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THE SITUPS*: Super Insulated Tilt-Up Panel System.

By Bales, Issue 63, Prefabricated Panels, Straw Bale Construction, Uncategorized, Walls One Comment

By Huff ‘n’ Puff Constructions

Editors Note: We plan to have a comprehensive article covering as many of the tilt-up straw panel systems on the global market as we can in Issue #64 due out in July.  Please also note that the images associated with the thumbnails on this page are of large size.  We wanted to keep them original size to allow you to see details clearly.

INTRODUCTION
Recent times have brought an increasing wave of environmental and energy efficiency awareness in the building industry throughout Australia.  This increased awareness of the effect of logging on our forests, lakes, and streams, as well as heightened concern for the energy cost and efficiency of our buildings and ever-increasing costs of construction materials is bringing tremendous pressure for change to the Australian building industry.

A primary focus of this change is the development of alternative forms of construction for single and multi-family housing as well as commercial and industrial buildings.  With a tradition that dates back almost 200 years, the Australian building industry has utilized timber extensively for use in wood frame construction, concentration on wood framing timber as the principal raw material for the structural shell of the majority of our housing and much of our light commercial structures has tremendously diminished our hard wood and softwood forest resources in Australia.

The cost of framing timber has more than doubled in the past five years. The price of timber is projected to continue to rise over the course of the next decade with additional concerns over the quality and availability of that timber.  The price and in some areas the availability of energy has added a new and important factor in most building projects.  With these facts in mind, the building industry, known for its rigidity and resistance to change, will have to look at replacement materials for framing timber in home and commercial construction.

THE SITUPS*
We are in the process of developing and bringing to the market place a unique, and ecologically sound, structural insulated panel building system.  These panels will be able to be put into place by two people.  This structural panel system provides a cost-effective, building system that is based on an environmentally responsible manufacturing process.

Huff ‘n’ Puff Constructions are manufacturing a structural super insulated panel that uses as its core material waste agricultural cereal straw from wheat and other cereals commonly grown in Australia.

SITUP Prototype

SITUP Prototype From TLS #24

With the recent high rise in energy costs and energy availability this product’s value to the builder and his client is a product that is more important now than ever before.  THE SITUPS* is highly competitive to conventional building methods.  With the reduced construction time, energy savings, non-toxic nature of the product, and strength and durability of the product indicate we have a building system whose time has come.

HISTORY
It was on the banks of the Murrumbidgee River at Hay that we made our first SITUP.  This event was first published in The Last Straw many moons ago now.  It involved a BIG chain saw and a jumbo straw bale 2.4 m x 1.2 m x 1.2 m (8’x4’x4’).  We made three panels out of the one bale and had a lot of waste with the “method” we used at that time.  Back to the drawing board…  [Huff ‘n’ Puff shared this technique in TLS #24, Winter of 1998]

01 Testing 2

Testing

In between building straw bale houses and wineries we kept on refining the process over the past 8 years.  Eventually we got an order to make 60 x 2.4 x 1.2 x 150 mm panels for a straw bale house that we were building in Kangaroo Valley, near Sydney.  These panels were to be used for the internal walls and are non-load bearing. 

We had these internal panels tested at the University of Western Sydney.  Our tests were to establish their load bearing and wind loading capacity.  They did not pass muster for load bearing but showed us their potential.  However the size of 150 mm wide proved to be very hard to manufacture and will need a lot of refining in the 03 Kangaroo Valley 1 (1)process to make them a worthwhile proposition.

FIRST LOAD BEARING PROTOYPES
After many experiments and research we have chosen a method that we feel has the potential to change the way we build with straw bales now and into the future.  We also realise that several straw panel systems are now on the market in parts of Europe and Canada.  Our opinion is that more is good and will only lead to the acceptance of building a house, flats and even high rise units and many other types of building by adopting straw as the medium in tilt-up wall technology.

07 Wagga Wagga 2 (3)

Near Wagga Wagga

We have now completed two SITUP buildings in New South Wales.  One close to home in a suburb of Wagga Wagga, and the other on a farm near Yass, which is close to Canberra.  We are now filling an order for a three-pavilion SITUPS home in the Hunter Valley of New South Wales.

11 Yass 1 (4)

Near Yass

The SITUPS are currently 2.450 to 3.000 metres high and come in various widths from 600 mm to 1.2 metres.  We can also make them between 350 mm and 450 mm wide.  The cladding can be a variety of material from renders to weatherboard, corrugated iron and many other forms of external sheeting.  Internally they can also be clad in render or Gyprock and various types of lining boards.

We are also developing a portable SITUPS factory to make these on a building site.

SUMMARY
The SITUPS will greatly reduce carbon emissions from new buildings through savings during manufacture and the operation of the building.  We already know this, having built many straw bale buildings since 1998 and together with 145 straw bale building workshops now completed.

Hunter Valley

Hunter Valley

Our goal is twofold; first, to reduce the carbon impact of modern buildings with the SITUPS and; second, to be able to utilize a waste product of our wheat and rice cereal growing in Australia where rice straw alone is burnt at an alarming rate.  Some one million tonnes goes up in smoke (particulates and carbon) every year.  Enough straw to build, say, 44,000 three-bedroom SITUPS homes on an annual basis and that is only from the rice grown in one area of Australia.

All the other benefits that come with straw bale homes that we have know of and practiced over the past 17 years apply equally to the SITUPS.  The main difference to conventional building with straw bales is that the SITUPS are uniform pre-compressed at time of manufacture and hence are very fast to build with, saving time and money.

* The SITUPS is a registered trademark of Huff ‘n’ Puff Constructions

John Glassford and Susan Wingate-Pearse, The Straw Wolf and My Little Wolverine
Huff ‘n’ Puff Constructions
“Jack’s Flat”
22-24 Moore Street
GANMAIN N.S.W. 2702.
AUSTRALIA
61 2 6927 6027 Work
0412 11 61 57 Mobile
[email protected]
http://www.glassford.com.au

Healthy Living, Healthy Building (Building an EcoNest)

By Bales, Design, Issue 62, Straw-Clay, Walls No Comments

By Elaine Brett

Finished WallsTwelve years ago I had never even heard of building with straw.  I lived in a four-bedroom colonial house in a subdivision in Maryland.  The conventional American Dream – good job, big house, nice cars, the monthly lawn service, the health club membership, 24/7 access to shopping …

Then on my 49th birthday came the American nightmare.  A wake up call from Mother Nature.  Sometimes she needs to smack you hard to get her attention.  My wake up was a cancer diagnosis that sent me spinning into a quest of asking questions and trying to understand “how could this happen to me?”

One path of my quest (probably driven by my background as a chemist) sent me questioning the chemicals in my environment: the food I was eating, the air I was breathing, the water I was drinking, the lifestyle I was living, the buildings in which I was residing and working.  The answers took me beyond the overt pollution of urban air and water to the hidden nooks of micro pollutants in synthetic materials, chemical food processes and endocrine disrupters in simple everyday products.

The quest also took me on another path.  I began looking for a place to live clean and chemical free, or at least as clean as is possible.  And that’s how I came to a small town in the North Fork Valley (www.northforkvalley.net) in Western Colorado.

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Straw House Patent (Feuillette House Follow-Up)

By Bales, Community, Design, Issue 62, Straw Bale Construction, Technical, Walls No Comments

As an update to this post about the Feuillette House in France, here is a patent in the United States for straw bale construction.  It was filed on June 6, 1921 and is a very interesting read for the bale construction history buffs out there. The author was Emile Feuillette himself and approved on June 6, 1921.

This is not the oldest patent on bale construction as we documented back in Issue #21 in the Winter of 1998.  That title goes to Josiah M. Leeds (of Indiana, not Nebraska) in 1880.  The article describes and contains illustrations of three subsequent straw bale building patents (1885, 1903, and 1905).  Issue 21 can be ordered on our CD of the first 40 Issues here.

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Book Review: Earth Render

By Issue 62, Plaster, Straw Bale Construction, Technical, Walls No Comments

Reviewed by Jeff Ruppert

Cover file  SmlEarth Render: The art of clay plaster, render and paints by James Henderson is a refreshing, easy approach to what can become an overwhelming process.  As anyone knows who has worked in the natural building trades, earthen materials are highly variable and therefore require a basic understanding of those variables.  James Henderson explains this process in a concise, easy-to-read format with plenty of illustrations.

What is nice about the approach of this book is that it is meant for the novice as well as the seasoned tradesman.  It can be followed by anyone and needs little introduction.  It focuses on how earthen materials are used to clad and finish walls, and that is it.  There are no lengthy chapters espousing the virtues of earthen construction.  Mr. Henderson assumes that you are reading his book to learn the finer points of his trade, and therefore an ethical discussion is not necessary.

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Traditional and Contemporary Natural Building in Korea

By Bales, Design, Energy, Floors, Issue 62, Plaster, Straw Bale Construction, Straw-Clay, Walls No Comments

By Kyle Holzhueter

Editors Note – This article is a feature length pictorial look at the various aspects of natural building in Korea.  The full-length article will be in the upcoming issue of The Last Straw and is available in its entirety right here on the website for subscribers.  Make sure you have a subscription soon so you won’t miss this stunning array of natural building techniques.

Traditional Korean Architecture

Traditional Building in Korea relied primarily on natural and local materials.  Buildings were traditionally designed according to the 間 (Korean: ka, Japanese: ken) module, a common measurement found in east Asia.

East Asian Modual

East Asian Module

Traditional Korean homes generally have a timber frame with adobe or wattle and daub infill, though regional variations are found throughout the country.

Traditional House

Traditional House

Regional Variation

Regional Variation

Especially on Jeju Island where volcanic rock and strong winds are abundant, homes traditionally consisted of a double wall system with an exterior wall of volcanic rock surrounding an interior wall, creating a protected corridor around the house.  This in turn, protected the interior walls from wind and rain and improved the thermal performance of the home.  Also because of the strong winds, thatched roofs were generally secured by a net of straw ropes.

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A Straw-bale Home in Idaho – TLS #55

By Bales, Design, Plaster, Roofs, Straw Bale Construction, Walls One Comment

This article originally appeared in TLS #55 and was the feature article in that issue.

house1by Wayne Bingham and Colleen Smith – Idaho, USA

Our interest in straw-bale construction grew out of our concern for energy efficiency. Our research into building energy efficiency grew into an awareness of sustainable building practices. An urge to build an energy-efficient home of materials that are sustainable grew as we explored these issues.

As we examined the site conditions for our home in Idaho, we found prevalent winds came from the southwest, passive solar orientation was due south, and views were predominantly southeast toward the Teton mountain range. The homestead to the west anchored the place visually and the rolling grass and grain fields to the north and east held their own hypnotic beauty.

We asked ourselves, “How do we place a building here and what would it look and feel like?”

From Small Strawbale by Bill Steen, Athena Swentzell Steen and Wayne J. Bingham. Published by Gibbs Smith

From Small Strawbale by Bill Steen, Athena Swentzell Steen and Wayne J. Bingham. Published by Gibbs Smith

We walked the site many times over several years, searching for the right place to build and the right kind of structure to build to respond to the soil, views, and
weather. When the irrefutable drive to build overwhelmed us, we went to the land and stayed for three days, walking, feeling, talking, and looking for the right place. We examined alternative ways of achieving solar gain while maintaining prominent views and avoiding challenging weather patterns.

The summer sun in our high mountain desert can be intense. The days can be hot, evenings cool down fast when the sun goes down, and the nights are cold. So a porch wrapped around straw-bale walls made sense to us. It can protect us from the sun, provide outdoor living space, and allow the straw bales and the internal thermal mass to moderate and maintain a relatively even temperature inside the house. The porch would also serve to protect the earthen-plastered bales from the weather.

We wanted the house to sit lightly on the land and allow the rolling surface of the earth to flow unimpeded past the house. We raised the porch surface only six inches above the adjacent ground around the entire perimeter to require only one step to grade.

We have visited and experienced several houses that deeply impressed us and we developed several drawings to reflect this approach. They were approximately square, had hip roofs and wrap-around porches. The deep porches were occupied with plants, chairs, tables, firewood, clotheslines, and other apparatus for living out-of-doors under cover.

After consideration of many schemes, we settled on one that is 34-ft. square, providing 1,156 gross sf and 961 net usable sf. Seventeen percent of the total area is in straw bales and the house is 83 percent efficient. It has a kitchen/living area, one bath, a master bedroom and guest room. There is a loft for the grandchildren.

Photos by Wayne J. Bingham

Photos by Wayne J. Bingham

Colleen had researched the area for organic straw bales that were 14-in. high x 18-in. wide. We found a farmer in Blackfoot, about 90 miles away, who had grown straw without herbicides or pesticides. Because the crop had matured and there was rain forecast, he cut and baled the straw. We had been working to have the house dried-in before taking delivery of the bales. We were able to place the bales under the newly finished roof before rains. Bale installation took only one week, notching and fitting under the roof and between columns and windows and doors.

Several friends called out of the blue and said that they heard that plastering was about to happen and could they come to help. Yes! Stan, John, Joe, Susan and I spent the weekend hand applying the beautiful chocolate colored earthen plaster mixed with long fibers of straw. We were at the end of summer and we wanted the plaster to dry before it could freeze, rendering earthen plasters no good. We were able to apply a rough coat on three walls over a three-day weekend. Brian and I finished the final wall in two days. The first weather coat had taken about one week. The building season ended and we left for the winter, planning to return the next spring.

diningWhen we returned in June 2003, we turned our attention to the final plastering on the main house. Sift clay, chop straw, mix clay to water, add straw and sand and apply to the rough coat completed last year. Check proportions, read the newly published book Natural Plasters, do tests and define how we want to do the work. Out of the research and study and questioning came a process we are very pleased with. We applied an infill coat of stiff plaster to the existing hand-applied rough coat using wood floats. We then brought the surface to within 1/4-in. of the /finish surface using a plaster that has more sand and less straw, sent through the chopper a second
time.

The final coat was applied with a steel trowel with curved corners, and polished with stainless steel Japanese trowels. It turned out quite nicely, with soft rounded corners and the bottom edge flared out to meet the metal drip edge.

We had read of clay “alis” paint. We read recipes in the two books and called the Steens asking for their advice. “Start with one part wheat paste glue, add two parts water, add clay until it covers your finger without showing a print.” We added one small scoop of burnt umber and about four cups of medium-sized mica flakes. We painted it on with 4-in. brushes, allowed it to become almost dry, and then polished with a damp (not wet) sponge.

Wow! What a difference it made. When plastering, the joints between one day’s work and another were visible, even though we tried diligently to feather it out. The alis unified the whole surface, and no joints were visible. It has a soft sheen from the mica, and it invites touch, as everyone who comes to the house exemplifies. Some have said it looks like leather. We think it looks like the earth around the house, but is refined by plastering and polishing. It looks like it belongs to its surroundings.

Building our house started out as a dream, a desire to do something sustainable, to build with one’s hands. Our project then became something physical, real, as we worked with the foundations, concrete, rebar, straw bales, earthen plaster, roofs, wiring, and all the rest.

In the summer of 2004, we installed a photovoltaic system to serve electrical needs of the house. We mounted the solar collectors on the garage porch. Batteries and inverter are in the garage with underground feeds to the house.

Well drilling estimates came in at $20,000, so we looked for another alternative. We built an 18,000-gallon underground cistern for a fraction of the cost that takes rainwater from the house and garage that passes through a filter before going to the tank. Before use in the house, it also goes through a charcoal and UV filter. It filled completely the first winter. With the exception of propane for heating and cooking, we are entirely off-the-grid. What a feeling of freedom!

Our home developed meaning for us beyond our wildest expectations. There has been a profound change in direction of our lives and satisfaction since we explored ways of becoming involved in sustainable building and focused on strawbale as a preferred method. Thirty-five years of life energy are focused on building our home. Feeling through our needs, responding to the site, and building the house day-by-day have been the most satisfying and meaningful experiences of our lives.

———————————————————————–

Wayne J. Bingham and Colleen F. Smith, a husband and wife team, have been involved since 1998 in straw-bale design and building. Their interest is an outgrowth of an exploration of energy efficiency and sustainable building techniques. In the mid-1990s, they attended several American Institute of Architect Green Building conferences where they began to understand the need for finding new ways to build without endangering the earth and its resources or future generations.  Seeking a direction of their own, they went on a natural building odyssey to the Southwest U.S. evaluating cob, adobe, rammed earth, earthship and straw-bale buildings, visiting or staying in each. They evaluated thermal performance, beauty, the feel, construction techniques and concluded that straw-bale building held the greatest possibility to satisfy their interest.

They attended The Canelo Project straw-bale and earthen plaster workshops and came away with a love affair with strawbale and earthen plaster that has not abated. Wayne immediately plastered their concrete block garden wall in their backyard with earthen plaster (see p 11 of this issue). They returned to the Steens in 1999 to spend a year involved with workshops, construction and collaboration with Bill and Athena on the development and production of Small Strawbale published in 2005 by Gibbs Smith Publishers.

Avid photographers and travelers, Wayne and Colleen have searched out and documented indigenous buildings in the United States, Greece, Great Britain and Italy and have developed a large library of images that were the start of the book. They took additional trips to explore and further record specific straw-bale buildings that now constitute a new book called Strawbale Plans.

In addition to Wayne’s working with owners and builders on straw-bale home designs and conducting workshops, Colleen and Wayne have put their experience into building this straw-bale home of their own in Teton Valley, Idaho. www.wjbingham.com

Birth of the Power Trowel: Pumping Without Spraying – TLS #42

By Bales, Plaster, Products, Straw Bale Construction, Technical, Walls No Comments

This article appeared in TLS issue #42.  This issue includes articles about experimentation and development of bales made from various types of materials.  Articles about methods and equipment for spraying bales with plasters appear in #43 Spraying Earthen Plasters in Colorado), #33 (Stucco Pumping Iron).

by Peter Mack – Ontario, Canada

 

Mud arrives cleanly and directly through the homemade “power trowel” attached to a stucco pump.

Mud arrives cleanly and directly through the homemade “power trowel” attached to a stucco pump.

Very early on in our careers as straw-bale builders, we realized that being able to pump plaster was going to be important if we were going to attempt multiple projects. Bodies and spirits just wouldn’t be able to keep up with endless hand-plastering. So, we bought an ancient pump and started spraying.

Oh, how I remember the days of the sprayer nozzle! The comforting “farting” sound, the reassuring overspray sticking everywhere, plaster in our eyes, noses, lungs, hair, shirts and sometimes ending up on the new roof of the house we were plastering (do not trip while spraying!). The nozzle end was a tiny opening 1/2 to 5/8inch(12-16mm), so if a tiny pebble made its way through the screening and into the nozzle, it could (and did sometimes, much to our chagrin) jam up and create back pressure, even to the point of exploding the hose. Luckily no one has ever been in the way of the hose at the time, but what a sorry mess it makes!

Devising a Solution. We talked often about improving the system. I had read about trowel ends for plaster pumps before, and this kind of fitting seemed like it would be cleaner and easier to use, but it seemed impossible to find one for a large stucco pump. As often happens in life, I set about to make my own. The first step was to buy some new supplies:

  • 8-foot(2.4m) length of 1-inch(25mm) rubber air hose
  • 6-inches(152mm) of 1-inch steel pipe threaded on the outside.
  • 1-inch inline swivel (grease twice daily!)
  • 1.5-inch(38mm) cam lock coupler, NPT threads
  • 2-feet(0.6m) of 3/8-inch(9.5mm) round and square bar
  • various 1-inch hose barbs and bushing reducers
  • aluminum hawk or similar sheet metal

elev1Then I followed these steps:

  • Make a 30-degree (approximate) bend in the 1-inch pipe, leaving an 11inch(280mm) section of the pipe straight at one end. Use an acetylene or propane/ oxygen torch and wind a coupler onto the threads or they will get bent!
  • Grind a flat face roughly 3/4inch(19mm) across along the straight, 11-inch section. This is where the trowel will attach.
  • Grind a slot through the pipe in the flattened section, 3/8-inch(9.5mm) wide by 5-inches(127mm) long, centred five inches from the bend. The plaster will exit through this slot.
  • Place the flat face on the workbench with bend up and weld on four reinforcement bars flush with the face. Use the 3/8-inch square bar. These are necessary to support the trowel attachment, as the trowel material is not strong enough by itself.
  • Weld on the handle. Shape to taste from 3/8-inch round bar, remembering that heavily gloved hands will be trying to hold the handle.
  • Lay out the trowel face. An aluminum hawk makes decent material. Our trowel has very rounded corners and is 12-inches long by 6-inches wide(305x152mm), with a 3/8-inch by 4-1/2-inch(9.5x115mm) slot. Bias the slot towards the end of the trowel by 1/2 to 1-inch to allow closer application to ceilings.
  • Use a drill and saber (jig) saw to cut the trowel out. File off sharp edges.
  • The aluminum is fastened to the steel pipe with polyurethane caulking and annealed steel wires twisted tight with pliers. Our earlier experiments using Lexan for the trowel, attached by 20 machine screws failed, lasting only one or two jobs.
  • The rest is basic plumbing: use Teflon tape on all threads and heavy-duty hose clamps. As we’re reducing the hose down to 1-inch, a full size quick-connect is necessary at the upstream end of the eight-foot hose to allow for proper clean outs.
  • After trying several types of plugs in the open end of the pipe and wasting too much time searching for them at clean out time, we’ve settled into a groove using hand cut plugs made out of styrofoam. They hold just enough that, if the slot plugs up, the pressure pops out the plug. Foam rubber would probably work just as well.

elev2A New and Valuable Tool. Thus was the birth of the power trowel. It worked!  No more overspray!  We won’t kid you…we still make a mess when we plaster, but at least it’s more controlled now. The power trowel needs two operators (or one if that person is truly a power-power troweler, such as Andrew McKay!). One person handles the hose, the other holds the trowel end up against the wall. The trowel end emits a continuous “ooze” of plaster (hence the nickname “Barfing Snake”), and the speed is controlled by the throttle on the pump.

The trowel can be either moved sideways across the wall, or more popularly, up the wall. If you are using an up-and-down motion, the trowel must be held perpendicular to the ground, catching the material being squirted until you can begin applying at the wall’s base again.

There is quite a knack to this grueling job, and the pairs who are quite talented at it actually seem to dance together as they pass the power trowel back and forth, weaving gracefully around scaffolding, rocks, bales and other typical plastering obstacles.

Advantages:

  • fills hollows, good penetration into bales, flattens mud as it applies
  • less clogging because of wider opening, can pass fibre mixes
  • blow off valve works
  • less back pressure, easier on pump engine and workings
  • less loss of paste and water to atomization, resulting in longer working times
  • no more overspray on windows, ceilings and people (although we do still drop a bunch on the ground/floor)

Disadvantages:

  • overhead areas difficult
  • does not quite reach ceiling, trowelers often have to push the mud up the last three or four inches(75100mm)
  • occasional air pockets between coats
  • somewhat more physical effort for the nozzle person.

We still sometimes reminisce about the old days of the “farting” spray, and will occasionally bring it out of the closet and take it for a test drive; once a friend wanted to record it for a CD, but do we really miss it? Not a chance! The power trowel has made life as plasterers easier, cleaner and quieter.

 

Peter Mack is a full-time bale builder and a partner in Camel’s Back Construction. He is co-author of the book Straw Bale Building (New Society Publishers). Contact: Peter Mack <[email protected]> www.strawhomes.ca

Finishing Bale Walls with Siding – TLS #57

By Bales, Building Science, Design, Plaster, Straw Bale Construction, Technical, Walls, Water 2 Comments

This article appeared in TLS #57.

Loose Strings: Technical Discussions
by Jeff Ruppert – Colorado, USA
T e c h T i p s

A little known fact in the bale building realm is that a handful of people scattered across different continents have experimented with the idea of finishing their bale walls with wood or some type of manufactured siding. The technical term for siding over a bale wall assembly is a “rain screen.” The use of a rain screen (sometimes referred to a “multiple defense assembly”) on a bale wall plays the role of keeping rainwater off of the bale portion of the wall. This is in contrast to the standard way of finishing a bale wall with plaster and allowing moisture to come into contact with it on a regular basis (also referred to as “faceseal” walls). In fact, almost all of the literature to date on bale-wall construction makes the assumption that they are faceseal assemblies.

In this article, we are going to take a look at the pros and cons of in-stalling siding over a bale wall. To some people the idea of not having a plaster finish on a bale house would seem weird, mainly due to aesthetic reasons. However, for those who have chosen to use siding, aesthetics take a backseat to function due to high rates of rainfall throughout the year, as well as constant high humidity. The option of allowing bale walls to even get wet in the first place is not an option and therefore other systems must be considered.

For those of us who live in drier climates, the consideration of moisture is not as dire, therefore giving us more choices. However, doesn’t the siding option make sense if you are concerned about moisture at all? If you would like to design a building with mixed finishes, such as a combination of plaster, masonry and siding, this would open up the opportunity to include bale walls as an option on those projects. In fact, by installing a rain screen over bale walls are we not greatly reducing the potential for moisture damage, as David Eisenberg puts it, by “designing problems out of the project” from the start? We will explore these issues and hopefully offer you another choice in your search for solutions.

Rain Screens
In the old days, a rain screen was simply an exo-barrier that was attached to a building to catch rainwater and shed it before it could hit the structure behind it. The Norwegians titled this approach the “open-jointed barn technique,” since originally it was used in conjunction with the construction of barns1.

With tighter construction and newer forms of finishes, the technology of rain screens has evolved into a science. One of the advantages of using a rain screen on a bale wall is that, no matter
how you do it, it will probably add a significant layer of protection that would otherwise not exist. This assumes that you do not install the siding to accidentally direct water into the wall. The potential exists for this to happen, so just like any other type of finish, pay attention to the details!

Siding over bale walls

Siding over bale walls

No matter what type of wall you build, the driving forces of moisture will be:

  • Air pressure difference (gradient)
  • Gravity
  • Surface tension
  • Capillary action
  • Rain drop momentum.

The dominant force acting on your walls will be the difference in air pressure across the siding itself.  As the wind blusters around your house, there are pockets of less and more pressure ever changing within and around your wall assemblies. The main goal is to minimize any pressure differences so water is not accidentally driven into the wall assembly. By minimizing pressure differences, the main force acting on nearby moisture will then be gravity, drawing water down to the ground where it belongs, before it reaches your bales.

In order to equalize pressure, an air gap behind the cladding (siding) needs to be well ventilated to the atmosphere. This can be achieved through different methods, but whatever you do, make sure not to create a gap for wind to blow rain behind the cladding. This means providing ventilation behind the siding so air can pass through easily, but including a barrier at the points of ventilation to keep wind-driven rain from entering.

The advantages of using a rain screen are:

  • Adds another option for finishing bale walls (aesthetic),
  • Keeps moisture completely off the bale portion of the wall assembly,
  • Provides replaceable/changeable finish,
  • Has low or no maintenance (depending on material),
  • Uses local materials in northern climates near forested areas.

The disadvantages of using a rain screen are:

  • Plaster finish is not an option on a bale wall,
  • May not be as durable as some types of plaster,
  • Materials may not be sustainable or even available in your area,
  • Aesthetic of siding may not match your project.

Rain Screen Concept on Bale Walls

It is important to remember that no matter how we finish bale walls, they must be sealed with plaster. This means that even if we choose to use a rain screen, we must apply at least one coat of plaster. One way to install siding on bale walls is to first install nailers for the siding. These can be in the form of 2-in.x2-in. wood strips attached to the sill plate and beam at the top of your bale wall.
We recommend attaching the nailers before stacking the bales, but you can do it afterwards if you like. Once the nailers and bales are in place, one coat of plaster is applied between the nailers. A rough coat of plaster over the bales is all that is necessary. Little or no troweling is required because no one will ever see the results. After plastering, building paper is stapled to the nailers and the siding is then installed, leaving a gap behind the paper for ventilation and drainage.

One issue of concern with this method is the gaps that can occur between the plaster and nailers as the nailer wood shrinks over time. These gaps can allow air to ?ow in and out of the bale wall, creating a loss of insulating value, as well as a path for insects and/or rodents. Extra care and/or the application of caulk can take care of these gaps. Also, these gaps can be eliminated if the nailers are installed after plaster is applied. Whatever you do, be sure that a gap remains between the back of the siding and the plaster.

This is but one way to install siding on to a bale wall. There are variations to this concept, but the goals remain the same – keeping rainwater and back-splash off your bale walls. Pay attention to the details and remember the forces that are acting on water that comes into contact with your walls. Holding these basic concepts in mind will help you design your wall system. And most important, do your homework first!

Happy wall building!

Resources
1. Rainscreen Cladding: A Guide to Design Principles and Practice.Anderson, J.M. & Gill, J.R. Butterworth-Heinemann, 1988.
www.shildan.com/Rainscreen/History.htmlhttp://irc.nrc-cnrc.gc.ca/pubs/ctus/17_e.htmlwww.greenhomebuilding.com/pdf/RainScreen.pdfwww.cmhc-schl.gc.ca/en/inpr/bude/himu/coedar/loader.cfm?url=/commonspot/security/get?le.cfm&PageID=70139

Ed.Note: Jeff encourages TLS readers to send in questions and comments to The Last Straw. There may be outstanding issues that builders are dealing with that most laypeople may not aware of. There are always many questions from people new to straw-bale construction. With this in mind, this column is offered and intended to encourage everyone to educate themselves to the fullest extent regarding building construction, and we are here to help in any way we can. This forum endeavors to offer the best of our knowledge, with no claim to its completeness, but to the spirit of bale building as a continuing evolution of one form of habitat within the larger realm of natural building. We offer this forum for dialogue, with no implication of being right or wrong. This forum is for you, the learner, artisan and teacher.

Jeff Ruppert, P.E., Principal, Odisea LLC, Ecological Building, Engineering and Consulting, P.O. Box 1505, Paonia CO 81428, 970.948.5744  <[email protected]> www.odiseanet.com
Jeff has been in the construction trades for over 25 years, beginning as a laborer and draftsman on his father’s construction projects. He has spent many years working on construction projects he designs, and is a licensed engineer in Colorado.

Build Your Own Simple Bale Wall Moisture Sensor – TLS #57

By Building Science, Plaster, Products, Straw Bale Construction, Technical, Walls, Water No Comments

This article appears in issue #57 of TLS.  There have been other articles about moisture sensors in recent years.

drillby Habib John Gonzalez – British Columbia, Canada

This article appeared in a slightly longer version in TLS#22/Spring 1998.

Here are the simple steps and materials needed to build your own bale wall moisture sensor:

1. Determine what depth of the bale you want to monitor and cut the 3/4-inch PVC pipe to that length.

2. Make the white pine sensor disk 1/8-in. thick to fit snugly into one end of the pipe.

3. Solder two lengths of telephone wire to two pairs of small bolts. One end of the pair of wires is bolted to a PVC pipe cap so the tips will protrude from the finished interior wall. The other end of the wires will be bolted to the sensor disk.

4. Use epoxy to glue the disk to one end of the pipe; run the wires through the pipe and fasten the other pair of bolts to the interior wall end cap. Glue the cap to the pipe.

5. Glue a perforated pipe cap over the sensor end of the pipe.

sensor6. The sensor is ready for installation in the bale wall.

7.The TimberCheck moisture meter is available from www.leevalley.com

8. A number of bale wall moisture studies were sponsored by the Canadian Mortgage and Housing Corporation (CMHC). You can get a summary of all of the CMHC moisture work on their web site www.cmhc-schl.gc.ca/publications/en/rh-pr/tech/dblist.cfm?mode=year.  Scroll down to the bottom of the list for 00-103 (year 2000, document 103) on straw-bale moisture monitoring.

schematic

 

 

 

1. Outer end-cap
2. Perforated PVC pipe
3. Wood disk with screws
4. Wires
5. PVC pipe
6. Inner end-cap
7. Screw contacts

Siberia 2008 (Altai Project, Builders Without Borders)

By Bales, Community, Design, Plaster, Straw Bale Construction, Walls 2 Comments

This is original content and has not appeared in the printed version of The Last Straw.

In mid August of 2008 we saw ourselves back on the plane to Siberia.  This was our second trip as a group of builders and teachers to this far-away and exotic place we now consider our most remote home away from home.  Paul Koppana (Crestone, CO), Cindy Smith (Durango, CO) and myself, Jeff Ruppert (Paonia, CO) were much more comfortable this time traveling half-way around the globe having made a trip for the same reasons back in the summer of 2005.  We were to teach and transfer our knowledge and skills building a straw bale structure to a group of eager folks near the city of Barnaul.  While the goals were similar, the region and our sponsors the same (The Altai Project, Builders Without Borders) , the exact location and the participants for this year were very different.  We looked forward to meeting everyone and seeing some old faces from our previous trip.  This is the story of our time in Southern Siberia in 2008.

Bale Walls with Clay Clip

Bale Walls with Clay Slip

img_0374

Model of the Building

We departed from Denver International Airport on August 16th and flew to Atlanta where we boarded a flight straight to Moscow.  We were greeted at the airport by our Czech cohort and friend Jakub Wihan (Kuba) who speaks enough Russian to translate for us.  Kuba was present on our 2005 trip and was now playing multiple roles.  Not only was he going to be teaching his skills of wall building but he was to also translate for us when he could with his limited Russian.  In 2005 we were escorted by our leader, Alyson Ewald of the Altai Project, who organized and raised the funds for our travel.  While she was still in the capacity of the two latter roles, she was raising a newborn back home in Missouri on Red Earth Farms.  We missed her on this trip but new she was doing something much more important.

We landed in Moscow on August 17, met Kuba and made our way into the city for a long wait (12 hours) until our flight to Siberia.  The temperature was nearly 100 degrees (F) and the humidity was hovering around 90%.  We ate food, exchanged money and slept on the floor of the airport as jet lag caught up to us despite our best efforts to remain alert.  Kuba was fresh from his travel from England so he remained awake while we caught some much needed sleep.  We boarded our flight around 11p on Aug 17 and attempted to sleep during the five hour flight through three time zones to the east.  We landed around 6a on August 18 very tired and happy to see our Altai friend and hosts.

Sill Plates with Coal Slag Insulation

Sill Plates with Coal Slag Insulation

While the region and some of the folks were familiar to us, the project for this trip was different than 2005.  We were asked to help build a gallery/conference building with attached office and kitchen space for the Institute of Architecture and Design in Barnaul on their “Dacha” land which is directly south of Barnaul about 20 kilometers as the crow flies.  The building was designed by the architecture students over the past couple years as an ongoing project within their curriculum.  The result was a beautiful building using straw bale walls that stood about 14 feet tall.  The design of the building incorporated large overhangs and wrap around porches to protect the walls from the harsh winter conditions of Siberia.  To say that we were impressed with the design would be an understatement.  We thought it was magnificent, but we had doubts as to our ability to tackle all of the work needed for the walls, and then have a roof installed.  Our Siberian friends would astound us with their abilities and hard work, but more of that later.

After landing in Barnaul we spent the next few days attending and participating in a seminar for many of the Institute’s important administrators and local officials, we traveled into Barnaul for an art exhibit by one of the students who was also one of our translators, and we visited family of one of the professors and ate dinner.  We spent these days talking with Lena and Sergei, our main hosts and the Deans of the Institute directing the project, about building details and what materials we would need.  There were already bales on the site and the foundation was freshly poured.  There was no wood for the frame, nor any mesh or clay for plaster.  Cindy and Kuba immediately began looking for a source of clay which would prove to be a long and difficult task.

Our first step was to have the carpenters install the sill plates.  These turned out to be 6×6 timbers that were nailed into the foundation with blocking every several feet.  The spaces between the sills were filled with coal slag, which it seems is commonly used as an insulating material in Siberia.  On Aug 21 we built the first post as an example for the carpenters, which they copied many times to creating all of the window and door bucks, as well as corner framing.  The top plate was to be flat 2x material layered with joints staggered at post locations.

Bale Stacking

Bale Stacking

By the 23rd of August the posts were installed and braced around the main gathering space.  We were pressed by our hosts to teach a “workshop” and educate everyone in bale-stacking.  Paul and I described how stacking bales worked and showed them how to re-tie a bale.  The bales were of marginal quality so treating them delicately was very important.  The eager participants soon took over and were stacking away.  Within an hour three walls were substantially complete and we made everyone stop due to the questionable weather approaching.  We needed to cover our work before it was soaked by rain.  The carpenters also needed to construct the top-plate assembly so the top bales could be installed.

All of the bales on the main room were installed by the 25th and we began using plastic lath, or mesh, to reinforce the joints between straw and wood.  Without a stapler, we attached the mesh to the wood with nails bent over and we had some of the students make pins out of wire for attaching the lath to the bales.  Much of this work was loose by the time we began plastering, but it was still good to have it held in-place with something.  By this time, no clay had been found despite a few forays by Kuba and Cindy into the neighboring countryside.  It seems that any people with a pit of clay did not want to share it.  We were in an ancient floodplain where the river had deposited silt and sand, but left little clay exposed that was available for use. It seemed very frustrating as loads of “clay” would show up that was not suitable as a plaster material.  Cindy was becoming frustrated and unable to find a solution.

By the 27th clay arrived as Cindy and Kuba had found a source.  It was good quality so Cindy had the volunteers begin applying a clay slip to the walls while others prepared cob to stuff into voids.  The work was fun and we could finally see the project happening.  Our hosts, however, had bigger plans.  We were asked our opinions about how far we could go during our three week visit.  We were scheduled to leave on the 31st which was less than a week away.  We strongly encourage our hosts to focus on the main structure and get a roof installed before attempting any more new walls.  They charmingly went ahead with their plan of having the lower walls framed, bales stacked and the shed roof framed.  At this point a group of twenty or so students showed up to work for a few days.  The results were nothing short of miraculous.  Where we thought they were flirting with disaster, they used all of the skills we taught them and managed to not only frame and stack the lower walls, but plaster them with two coats of plaster before we left.  We were amazed!

Having witnessed how slow things can go in Russia, we could not believe the motivation that was instilled by our hosts in their students and other volunteers.  Not only were they dealing with the workshop, but they had a budget that was running out and needed to be refunded by the Institute.  If they failed to meet certain deadlines the building would not be finished.  We watched Lena and Sergei expertly navigate a sea of regulators, engineers, administrators and volunteers, all the while smiling as we appraoched never missing an opportunity to treat us like family.  The experience was humbling to say the least.

Students and Volunteers

Students and Volunteers

As the clay slip was applied to the building, we asked about electrical wiring.  No electrician had been hired and we were getting ready to seal the walls.  I created an electrical plan with Lena and some students, some wire was produced along with boxes.  The boxes were nailed to posts and lathed in-place.  Wiring was run up the posts through the top plate where all wiring would be figured out later.  We decided on the location of the electrical panel so I could plan where runs would be made later.  It was another last-minute detail, but we were able to do what we needed before it was too late.

Most of the plaster was mixed by hand due to a malfunctioning mixer.  We limped the mixer along until it was completely dead and then had the students team up in groups to make plaster.  They were able to keep up well with the dozens of people applying it.  By the time we left, a slip coat and one coat of plaster had been applied to the entire building.  Plastic tarps were used to protect the tops of the walls and drape over the rafters of the lower roof.  We held our breaths praying for dry weather.  We had seen rain on and off most of our visit, but not in large quantities.  All we could do was hope for the good fortunes of our amazing friends to continue.

We received pictures of the final building just before Christmas.  The building has been completed!  They have lime-washed the earthen plaster and installed siding where needed.  The roof is on and the interior is finished.  There are two truth windows that are the largest we have ever seen.  They didn’t seem to be swayed by opinions such as “the plaster is a rigid part of this structure.  Leaving it off large expanses of wall may not be desirable,” or “If bugs and rodents do get inside your walls, it will be like a movie theater for visitors.”  The desire of these folks to push their limits gave us pause at times and we are impressed by their resolve in the face of possible disaster.

Clay Delivery

Clay Delivery

Lessons were learned about working with the locals even if it meant doing something in the wrong order or what seemed to be the wrong way to us.  They have their ways of doing things and even though we thought we could help them, there was great resistance to our ideas at times.  Stepping back and letting the owners of the project remain in control no matter what was happening seemed to give them a sense of determination that would not be derailed.  It turns out that they did not ignore or resist our ideas as we had thought.  They listened and integrated them into their program in the best way they could.  What became clear to me was that we were working with formally trained architects and students of the classical ways of architecture.  They paid attention to details and form.  On this project the function drove their form more than what seemed typical.

Finished Building

Finished Building

This building took all of the lessons they were taught about bale buildings and integrated them in a very functional way.  They used large overhangs.  There was not a single bale wall over 2 feet in height that was not protected by a wrap-around porch.  They used earthen plasters even in their extreme climate where temperatures reach -50 degrees (F).  They finished the plasters with a lime wash that will be easily maintained over time.  They installed two huge masonry fireplaces as thermal mass.  There is almost no solar gain due to the dense forest so they reduced glazing on all walls to what was necessary and functional.

Truth Window

Truth Window

We left Krona on August 30 after a quick award ceremony where everyone received some thank you certificate and a book on the design of straw bale houses – a first of it’s kind in Russia.  Our next stop was the old building that we helped build back in 2005.  That project was 6 hours south by car so we kicked back as best we could in the smallest car we could imagine and rested until we arrived in the heart of the Altai Republic and back in Chemal at The Milky Way.  We were interviewed by a video production group and welcomed generously by our previous hosts.  They had erected a handful of wood-framed cabins for guests and used the bale building as a tourist attraction and gathering space.  The plaster is holding up much better than we thought.  It is also earthen with a lime wash.

The 2005 Project near Chemal

The 2005 Project near Chemal

On Sept 3 we were in Barnaul and boarding a plane back to Moscow and then onto Colorado.  It was another magical trip and one that was more successful than any of us thought possible.  The memories of bania (sauna) with friends every other night, meeting the families of our Siberian friends, working alongside our gracious hosts Lena and Sergei, and dancing around the campfire with all the volunteers who showed up for two weeks to help us and learn how to build with bales made for a deeply rich experience.  We look forward to seeing everyone again some day and to visit those two important projects that brought straw bale construction to the Altai region of Siberia.

We would like to thank the following organizations for their contributions and hard work:

The Altai Project
http://altaiproject.org

Trust for Mutual Understanding
http://www.tmuny.org

Builders Without Borders
http://builderswithoutborders.org

Institute of Architecture and Design in Barnaul

Fund for 21st Century Altai

Earth Plastering Guidelines for Finishes – TLS #43

By Bales, Building Science, Plaster, Technical, Walls One Comment

This article appeared in TLS #43.

by Gernot Minke – University of Kassel, Germany

Note: This article is excerpted from Earth Construction Handbook (by Gernot Minke, WIT Press, Southhampton, Boston, 2000) which contains further information about weather protection, physical and mechanical properties of clayey soils, treatments and additives and modern earth construction techniques worldwide.

blocks1) General. Earth plasters mainly consist of sand and silt with only as much clay as is necessary (usually between 5% to 12%) for developing their adhesive and binding forces. It is difficult to state what the proportions of an ideal earth plaster should be, because not only does the proportion of clay, silt and sand influence the properties, but also the grain size distribution of the sand fraction itself, the water content, the type of clay, the method of preparation and the additives. In order to test the appropriateness of earth plasters, samples with varied compositions should be tested. Earth plasters stick very well not only on earth surfaces, but also on brick, concrete and stone surfaces, if the surface is rough enough.

2) Preparation of substrate. As earth plaster does not chemically react with the substrate, the surface has to be sufficiently rough in order to develop a good physical bond. A good method of getting a strong bond is to wet it sufficiently until the surface is soft, and than scratch diagonally patterned grooves with a small rake or a nail trowel. In order to ensure that the plaster adheres better, it is also possible to use latching in the form of galvanised wire mesh, plastic mesh, reed mats, and such on the substrate before plastering.

3) Composition of earth plaster.

3.1 General. In order to get earth plaster free of shrinkage cracks, the following points must be kept in mind:

  • The earth should have enough coarse sand.
  • Animal or human hair, coconut or sisal fibres, cut straw or hay should be added (however, too much of these additives reduce the ability of the plaster to adhere to the substrate).
  • For interior plastering, sawdust, cellulose fibres, chaff of cereal grains or similar particles can also be used as additives.
  • In order to develop enough binding force, the adhesive forces of the clay minerals should be sufficiently activated by adequate water and movement.
  • When the plaster sticks to a sliding metal trowel held vertically, yet is easily flicked away, the correct consistency has been achieved.

In order to test the characteristics of an earth plaster, a simple adhesion test can be carried out. The plaster to be tested is applied 2cm(3/4-inch) thick to the flat surface of an upright burnt brick. The plaster has to stick to the brick until it is totally dry, which might take two to four days.

If it falls off in one piece by itself, as seen in the left sample of fig. 3-1, it contains too much clay and should be thinned with coarse sand. If it falls off in portions after the sample is hammered on the floor like the second sample in fig. 3-1, then it has insufficient binding force and should be enriched with clay. If the plaster sticks to the brick but shows shrinkage cracks, like the third sample in fig. 3-1, it is too clayey and should be slightly thinned with coarse sand. However, it can be used without thinning as the first layer of a two-layer plaster. If the surface shows no cracks and the plaster does not come off when hammered, as in the fourth sample in fig. 3-1, then the sample might be adequate. In this case, it is advisable to make a larger test about 1x2m(40×80-inches) high on the actual wall. If shrinkage cracks now occur, this mixture needs either to be thinned with coarse sand or mixed with fibres.

3.2 Exposed exterior earth plasters. Exposed exterior plasters have to be seasonably weather resistant or must be given perfect weatherproof coating. It is important in cold climates that the plasters together with their coating have a low vapour diffusion resistance, so that water condensed in the wall can be easily transported to the exterior. The exterior plaster must be more elastic than its ground in order to meet thermic and hygric influences without cracking. In general, for cold climates, an external earth plaster is not recommended unless sufficient roof overhang, plinth protection and good surface coating can be assured.

Since plastered wall edges are very easily damaged, they should either be rounded or lipped with a rigid element. In extreme climates when the elasticity of large expanses of flat plaster is insufficient to cope with the influences of weather, vertical and horizontal grooves filled with elastic sealants are recommended.

table3.3 Interior earth plasters. Interior plasters are less problematic. Usually they create no problem if they have fine shrinkage cracks because they can be covered with a coat of paint. Dry earth plaster surfaces can be easily smoothed by wetting and being worked upon with a brush or felt trowel.

If the surface of the walls demands a plaster thicker than 15mm(5/ 8-inch), it should be applied in two layers, with the ground layer containing more clay and coarse aggregates than the second layer. If the ground layer gets shrinkage cracks, it is not problematic, but could actually help by providing a better bond to the final layer of plaster.

Adding rye flour improves the surface against dry and moist abrasion. The author has proved by testing that this resistance can also be built up by adding casein glue made of one part hydraulic lime and four to six parts fat-free quark, borax, urea, sodium gluconate and shredded newspaper (which provides cellulose fibre and glue). The mixes in the accompanying chart worked well.

Lime reacts with the casein within the fat-free quark forming a chemical waterproofing agent. A similar reaction is obtained with lime and borax (which is contained in the shredded newspaper). Sodium gluconate acts as a plasticizer so that less water needs to be mixed for preparation (thereby reducing the shrinkage). Urea raises the compressive and the tensile bending strength, especially with silty soils.

Waste paper shreds lead to better workability and reduce shrinkage. The mixes B, C and E showed best workability. When using mixes A and E, it is preferable to first mix the casein glue and the shredded newspaper together with the water, and then, after an hour, add earth and sand.

With all mixes, it was found that the final smoothing of the surface, which was done by a felt trowel, was best done after several hours or even a day.

4) Guidelines for plastering earth walls. As pure earth plaster does not react chemically with the substrate, it might be necessary to treat the substrate suitably so that sufficient bonding occurs. The following guidelines should be kept in mind:

1. The surface to be plastered has to be dry, so no more shrinkage occurs.

2. All loose material should be scraped off the surface.

3. The surface should be sufficiently rough and, if necessary, moistened and grooved or the mortar joint chamfered, as described in section 2.

4. Before plastering, the substrate should be sufficiently moistened so that the surface softens and swells and the plaster permeates the soft layer.

5. The plaster should be thrown with heavy impact (slapped on) so that it permeates the outer layers of the ground and also achieves a higher binding force due to the impact.

6. If the plaster has to be more than 10-15mm(3/8-5/8-inch) thick, it should be applied in two or even three layers in order to avoid shrinkage cracks.

7. To reduce shrinkage cracks while drying, the mortar should have sufficient amount of coarse sand, as well as fibres or hair.

8. To improve the surface hardness, cow dung, lime, casein or other additives should be added to the top layer.

9. In order to provide surface hardness and resistance against wet abrasion, the surface should be finished with a coat of paint[Editor’s Note: breathable paint].

10. While using plasters, the change of physical properties caused by additives and coatings should be kept in mind especially with respect to vapour diffusion resistance.

decorative5) Sprayed plaster. A sprayable lightweight earth plaster with high thermal insulation containing shredded newspaper was successfully developed by the author in 1984. This plaster can be applied in a single layer up to 30mm(1-1/4-inch) thick using an ordinary mortar pump. In order to get a shorter curing period, some high-hydraulic lime and gypsum was added to the mixture.

balls6) Thrown plaster. Fig 6-1 shows how a traditional African technique, which consists of throwing earth balls on a wall, has been adapted. Here, this technique is used on a wood-wool board for a winter garden wall. In order to increase the adhesion, bamboo dowels were hammered halfway into the board.

7) Wet formed plaster. As loam plaster retains its plastic state for a long time and is not corrosive to the hands like lime or cement plasters, it is an ideal material for moulding with the hands. Fig. 7-1 shows an example of an exterior loam wall stabilised by a lime-casein finish.

Professor Dr.-Ing. Gernot Minke is a professor at Kassel University and a consultant structural engineer since 1967. He has a keen interest in earthen structures and low-cost, low-impact housing. He numerous publications include the Earth Construction Handbook (WIT Press, Southhampton, Boston, 2000). Contact: <[email protected]>

This article was submitted by Friedemann Mahlke, a student of Dr. Minke and a straw-bale builder and researcher. Contact <[email protected]>

Bale Preparation – TLS #50

By Bales, Plaster, Straw Bale Construction, Walls No Comments

This article originally appeared in TLS issue #50, 2005

Load-bearing walls waiting preparation

Load-bearing walls waiting preparation

by Tony Caniglia – Colorado, USA

This technique was developed to reduce the amount of fill with loose straw or straw/clay required when the bent (rounded) sides of the bales are butted together. The purpose is to remove the bulge on the ends of the bales so that the bales are squared up and fit right up tight together.

Prepping the bales before stacking them can help make them nice and square.  Do this somewhere away from the house or building for fire safety, to keep the dust away from other workers, and to collect the loose straw that will be created.  Start with a large number of bales. Use a couple of other bales to help hold one bale stand up on end. With your chainsaw, cut downward a few inches next to the strings on the end of the bale and move the chainsaw out toward the edge of the bale.  The bales may have a little roundness between the strings, so clean that area up, too. Try and keep your chain saw level, and don¹t hit those strings! Step back to eyeball it to see if the bale looks square. Clean up 6 to 10 bales, then set the chainsaw down and flip all the bales over to stand them up on the other end, and do the other side. You may have to lay the bales on edge and, with a little jump, put your knee into the bale or hit it with a sledge hammer if it has a curve to it. You could also lay the bales flat on top of a bench, if you don¹t want to bend over or want to keep the bale stable (another person working with you can help make this work easier, too).

You may occasionally hit a string with your chainsaw, say one out of ten, but it is easy to restring the bale. Just tie another piece of string  about 16 inches long to the cut string and make a loop knot on one end. Put the other end through the loop, crank it down (pull it tight) and tie it off.  Once square, the bales push together better and will help make the walls more stout with less voids. This means little or no stuffing with loose straw. When the bales are stacked, grab a 4-ft level, a couple of sledge hammers (or other ³bale bangers² as you prefer) and get another person to help. One of you should stand on the inside of the wall and the other one on the outside of the wall. Smack the bales so they don¹t overlap one another too much. Focus on getting one side as plumb as you can (for example, work on getting the inside plumb). Now trim the surface of the bales on both sides of the wall (inside and out) with a chainsaw or weed whacker. Be sure to do the whole wall, top to bottom. That will help to finish cleaning up any overlapping bales and any humps, bumps and lumps. This nice, plumb wall will make your lathing, netting, plastering and troweling process easier, not to mention the money you will save in stucco materials! And these beautiful, straight walls may make your building easier to sell in the future!

Sustainable Living in California – TLS #59

By Bales, Design, Walls No Comments

This article appeared in TLS #59.

semmes1Turko Semmes is a licensed general contractor from San Luis Obispo County, California, and one of the foremost experts in straw-bale building techniques.

semmes2A graduate from the Architecture Department of Cal Poly State University in 1978 with a degree in Construction Engineering, he has been self-employed since that time, running a custom home building business specializing in energy efficiency and sustainable building techniques. Turko is a co-founder of the California Straw Building Association. He has built several custom homes, agricultural buildings, and wineries throughout central California. He has taught classes and workshops on sustainable building systems to community groups and to students at the elementary, secondary, and university level. He is recognized as an expert on passive solar design concepts and other energy efficient techniques, as well as nontoxic and sustainable building materials.

semmes4The Semmes southwest-style straw-bale home (pictured here) is nestled in the Los Padres National Forest in a setting that joins nature with natural building. The courtyard/pool area is an inviting setting filled with flowers and hand-painted artwork at the main entry door leading to Turko’s office and the family den. The lower terrace provides space for relaxing poolside with an outdoor shower nearby. The upper terrace is a covered outdoor cooking and dining area. The formal living and dining rooms and the master bedroom face onto the meadow with views toward the mountains of the Santa Lucia Range. The cool and calming color palette of the master bedroom contrasts with the bright and lively colors of the other living spaces.

semmes5Turko Semmes, Semmes & Co. Builders, Inc., Atascadero CA
<[email protected]> www.semmesco.com
semmes3Photo credits: Semmes & Co. Builders, Inc.

 

 

 

Lime Mortars DVD Review

By Plaster, Products, Technical, Walls One Comment

 

What is the ratio of your mix?  Let your sand tell you!

This article is original content and has not yet appeared in the printed version of The Last Straw.

St. Astier Natural Limes, a producer of hydraulic lime products from France, is offering a set of DVD videos called The Master Stroke DVD Tutorial Series.  The Master Stroke is a 4-disc series beginning with lime mortars.  Other discs cover plastering and rendering with lime, and building and pointing with lime.  In this article we will review the first in the series, Making Lime Mortars.

The content of the DVD is laid out very clearly and is easy to follow.  The quality of the video is very polished. The main purpose of the DVD is to show the construction worker how to create a consistent, high-quality mortar or render.  Tips include how to properly keep your sand dry, how to measure each bucket of sand, etc.  But there was one piece of information that really make this video important.  Nearly half of the video is dedicated to the concept of the sand void ratio and how it affects your mix.

Have you ever wondered where the ratios we use for our mixes come from?  This video explains how they are derived.  Without going into too much detail, the ratio of sand to lime is determined by finding the void ratio of your sand.  Once you know how much air is between the grains of sand you can find the volume of binder.  If you use too much binder, the sand particles will be far apart, separated by water and lime.  If you use too little lime you are not filling all the voids with lime and you will have pockets of air and water.  The perfect ratio is one that fills all the voids and leaves little room for air or water.  Once you know this ratio, based on your sand, you can then adjust the ratio to achieve your desired results.  Don’t think you can just figure this out on your own through this article.  There is a proper way to do this, and each step is clearly defined in the video.

To know the proper ratio of sand to lime (or any other binder – clay, cement, gypsum, etc) is like an enlightenment for most of us.  Have you ever wondered why the code says 4:1:3/4 (sand:cement:lime), or why your friends used 1:2:9 (cement:lime:sand)?  Now you don’t have to guess.  This video will teach you how to properly measure the void ratio of your sand and the ratio of sand to binder.  It will become apparent that the mix your friends are using on their project has little bearing on your mix.

Mortars, renders and plasters all folow the same ratio and mixing concepts.

Mortars, renders and plasters all folow the same ratio and mixing concepts.

Learning how to derive the ratio of sand to binder is obviously very valuable.  The rest of the video walks you through the measuring and mixing process, showing how a professional would prepare his or her mortar.  After being a sub-contractor and mixing thousands of batches of plaster, this video would have been great as a tool for estimating.  In my mind it creates a baseline for high-quality that a builder can use to determine costs.

In summary, I would say buy this video!  It can be purchased at the link above for $39.  From novice to professional, you will find value.  Good luck.

This review is intended to be objective.  No compensation of any form has been accepted in connection with this article.

Straw-bale Sound Isolation and Acoustics – TLS #53

By Building Science, Design, Sound, Straw Bale Construction, Technical, Walls One Comment

This article appeared in TLS #53.  The topic of this issue is Moisture.  It contains an extensive article about Moisture Basics and Straw-Bale Moisture Basics (by John Straube, edited by Bruce King)  it also includes articles on moisture meter accuracy, moisture sensors, seismic resistance, and plaster testing.

by Rene Dalmeijer – The Netherlands

In June 2003, Jasper van der Linden, a building engineering student at the Eindhoven Technical University, Eindhoven, The Netherlands, tested the sound isolation of an earth-plastered straw-bale wall. Rob Kaptein of RAMStrobouw and I assisted in carrying out the test. The test was executed in a true acoustic test chamber according to ISO 140-3. We were able to execute a consistent test giving a good indication of how well a plastered straw-bale wall retards sound.

Based on the outcome of the test, it is to be expected that a reasonably well-designed and built straw-bale wall without acoustic defects (like protruding post-and-beam members) will perform in the region of 53dB and upwards (55dB with A weighting; “A-weighting” means the impedance is corrected to approximate human hearing sensitivity, which varies depending on frequency). The 2dBA increase in performance when compared to the test is mainly because we used very thin (worst case) plaster thickness in the test sample. Normally earth plaster finishes would be thicker. This puts the performance of a straw-bale wall at more or less the same level as a decoupled brick cavity wall and even exceeding it in the critical low-frequency region.

Most everyone who has been in a straw-bale building has had the sensation that interior sounds somehow seem louder, because interior sounds become more distinct for not being drowned out by background noise coming from the outside. This is a clear indication that straw-bale walls work very well as an acoustic insulator. Normally built structures depend on high mass for good sound insulation. But there is also another way of achieving good sound insulation, which depends on a damped cavity surrounded by two not-sostiff membranes with sufficient mass. A straw-bale wall, specifically with earth/clay plasters, is an excellent example of this alternative way of achieving good sound insulation, as the test result clearly illustrates.

The Test

The test was executed in the acoustic lab of the Eindhoven Technical University. The test and test facility is according to ISO 140-3 which is to test the sound isolation of building aperture of two acoustically separated chambers (the test sample is placed in an aperture between the chambers). Although I am aware of the limitations of the test facility for testing a wall system, we have endeavored to make this test as accurate and as representative as possible. The aperture’s size (ISO 140-3 std) is 1.88m2 /20 ft2. The tested straw-bale wall section had the following configuration:

  • Two-string (460mm wide building quality bales laid flat density 120-130kg/m3)
  • Earth/clay straw plaster 25mm and 35mm (intentionally asymmetrical cover)
  • No reinforcing plaster netting or mesh or any form of pinning

table1The chosen sample structure was to be as representative as possible of a normal earth/clay plastered straw-bale wall structure as used by the experienced straw-bale builder Rob Kaptein of RAMstrobouw. Rob was also responsible for manufacturing the test sample. The graph and table summarize the test result.

[Rene’s comment on the measured performance: The result can be expressed as 53dB according to A-weighting. Actually expressing the sound isolation value in one number (i.e., 53BA) is a simplification. In actual fact, giving the performance at each of the various frequencies is much more meaningful.]

Generally this is done at either one octave intervals (1/1oct) or at one-third octave intervals (1/3 oct), the last giving even more detailed information.The graph and table show both measurements (not A-weighted). The dip at around 250Hz is due to the transition between the masws and damped cavity odes of operation of the test sample and should be largely disregarded as part of the vagaries of a test.

The 53dBA test result might seem low but in fact is very good. Most conventional wall systems including a brick cavity wall with much higher mass have a lower performance. Specifically interesting to note is the 2-3dB better performance at very low frequencies of the straw-bale test sample when compared to brick-wall systems. Nearly all wall systems, including stick frame, are able to sufficiently subdue high-and mid-frequency sound, but low-frequency sound is problematic. In practice, better performance at low frequencies is worthwhile because it means that the ever-present background noise in suburban areas is perceptibly reduced.

Recipe for Straw-bale Wall Acoustic Isulation

Besides sheer mass, low stiffness with sufficient mass and acoustic decoupling are very imortant for acoustic sound insulation. The relatively low stiffness of a straw-bale wall with earthen plasters is ideal. The fact that the cavity between the two plaster shells is filled with straw provides excellent acoustic damping. Beware and be careful to fill all cavities and voids with very light straw/clay. Avoid any direct mechanical contacts between the inner and outer plaster shells, as these will seriously degrade sound damping performance. Contrary to what you would expect, loosely packed bales will perform better than very tightly packed bales. Extra thick (>35mm) earth plaster specifically improves low-frequency performance. Cement and lime plasters perform almost as well but earth plaster with lots of straw is the best due to a lower modulas of elasticity (stiffness). Applying significantly asymmetrical plaster thicknesses helps to avoid coincident reverberation of the inner and outer plaster layers. The thicker plaster layer should be on the sound source side of the wall. Pay a lot of attention to all openings and edge details; these are the weak points. An air leak of only one sq. mm will seriously degrade performance. Door openings and windows are literally acoustic holes in the wall; these need special detailing and attention to even remotely approach the acoustical (and thermal) performance of the surrounding walls. Even double doors generally show poor performance compared to the wall. The gaskets and seals in the doors should be double or even triple, but even then there is a problem as, over time, the seals will degrade and leaks will occur. The type of door you are aiming for is more like a steel watertight door in a ship than a house door with multiple closing bolts and tightening clamps. (All of this only if acoustical performance is essential.)

table2In conclusion, I would like to emphasize that, due to the nature of a straw-bale wall (an excellent sound barrier), the wall is not the problem; the connections between the

wall and all other elements incorporated or surrounding it are. In other words, it is the same issue as with thermal and moisture performance. I strongly suspect that most sound isolation tests executed on straw-bale walls are measuring the defects of other structural components or mistakes in the test procedure (a non-calibrated sound source, background noise, and such).

Room Acoustics

Here are some simple rules of thumb depending on the type of acoustics you want, e.g., very lively to very well damped. Soft acoustic instruments require a “live” (reflective) room. Loud amplified sound needs a “dead” (absorbtive) room. The single most important parameter is the reverberation time and level. The harder the surfaces, the livelier the sound. A bathroom is lively, hence your strive to sing even if you can’t. The opposite is standing on top of a snow-bound hillock [small hill or mound] – virtually no sound reflects back to your view. The bigger and harder the room, the longer the reverberation time, e.g., a cathedral. Next the relative dimensions: an oblong box (like Concertgebouw Amsterdam) approaches the ideal. Preferably the relative dimensions are approximately 2 to 3 to 5; this ratio will avoid the formation of dominant harmonic resonance and standing waves. The exact ratios needed for a given acoustical requirement depend on the size and acoustic reflectivity. I personally prefer rooms without parallel surfaces, thus avoiding standing waves. I think if you finish a room with earth/clay plaster on straw-bale walls, with wooden flooring and a well-pitched ceiling, you will have quite acceptable acoustics for musical performances. If it’s too lively, you can always add some damping afterward by placing soft furnishings in the room or hanging curtains on the windows. A bigger audience also helps.

Good acoustic isolation is definitely one of good merits of straw-bale walls. It should be seriously considered for purposes where sound isolation is of importance. It would be hard to find a more affordable solution to building sound studios, quiet houses in noisy neighborhoods, or noisy workshops in residential surroundings.

<[email protected]>

Rene Dalmeier has been interested in straw-bale building since 1998. In June 2005, he finally took the plunge and turned his hobby into a profession by becoming a full-time straw-bale builder.

A whisper = 15 dB … Normal conversation = 60 dB. dB: Abbreviation for decibel(s). One tenth of the common logarithm of the ratio of relative powers, equal to 0.1 B (bel).

Sill Pan Design Detail – TLS #51

By Bales, Straw Bale Construction, Technical, Walls No Comments

 

Slope pan flashing to outside.

Slope pan flashing to outside.

Included in TLS #49 (Myths and Realities, Spring 2005) was a discussion of ways to deal with moisture at the bottom of windows. David Eisenberg shared a written design detail for a pan under the window to carry water away from rather than down the wall. We wanted to share a drawing of this detail and David kindly provided one for us to share in Tech Tips.

Here’s the portion of the discussion in which David details this design idea.

“Protecting the bales beneath the windows requires that you catch the water under the window and make sure it gets all the way out of the wall. In other words, ideally, you would have a pan of sorts under the window, sloped slightly to the outside, extending a bit beyond each side and with a lip at the back and on each end (so water can’t just run off the ends), and extending out beyond the exterior wall surface, with a drip edge – so that any water that leaks through or runs down the sides of the window ends up in this pan and is shown the exit. You can make these pans out of metal, plastic, ice and water shield, cast this shape into a concrete sill, anything that will keep the water from leaking through it, but the principal thing here is to make sure that the water can’t get into the wall below the window. You can put your window sill material, whatever it is, on top of this pan flashing being careful not to punch unsealed holes when you install the sill. It can take a little thought and ingenuity to do this, but it assures you that, when the windows leak, the water leaves the building.

sill2

Concept of pan flashing turned up at back and sides extending beyond exterior finished wall with drip edge. Extending behind finish or trim at each side of opening.

“That old practice of just putting roofing paper or plastic over the top of the bales and setting your windows on it and then plastering over it just leads the water down inside the plaster to the bales wherever the water protection ends unless it runs continuously down the wall under the window to below the bales (and we don’t recommend doing that).  It just temporarily moved the problem down, didn’t solve it.”

Why We Build with Earthbags – TLS #55

By Roofs, Walls 4 Comments

This article originally appeared in TLS #55.  This article is one of several natural building materials covered in the issue. There are earthbag articles in these other issues: #52 An Earthbag/Papercrete House; #28 Earthbag Construction; #16 Earth Shoes: Earthbags (used as foundation); #57 Earthbag Structures in Disaster and Poverty-stricken Areas.  Subscribe to TLS to enjoy more articles like this or purchase back-issues at The Last Straw website.

by Kaki Hunter and Doni Kiffmeyer – Utah, USA

earthbag1We live in the heart of the great Southwestern United States, surrounded by examples of one-thousand-year-old ruins left behind by the ancient civilizations of the Anasazi, Hohokam, Pueblo and many others. It was these original natural builders that inspired us to consider building with earth as a way to create beautiful, low-impact, energy-efficient housing that has endured the test of time to this day.

We started by teaching ourselves how to make adobe bricks, the most common earthbuilding technique native to the U.S. Making adobe bricks turned out to be a lengthy process that involved mixing the mud, pouring it into forms, lifting the forms, and then turning the blocks over the next several days to facilitate even curing. The blocks then had to be stacked and protected until ready for use. Manufacturing the adobes required a considerable amount of space for both the pouring process, as well as for storage of the dirt needed to make them, and then the storage of the adobe bricks themselves until they were ready for building. We live right in the heart of a small town, which made this process a little tight.

The dirt for adobe block and most other forms of earthen architecture require a specific ratio of clay to sand, ideally about 25 to 30 percent clay to 75 to 70 percent well-graded sand. In some cases, a stabilizing agent may be added to an earthen soil to increase its compressive strength and make it resistant to the affects of water. Some earth building techniques like cob require copious amounts of straw fiber added to the mix. In most cases, adobe brick also benefits from the addition of straw or some other kind of natural fiber.

Honey Home

Honey House

After our initial foray into homemade adobes, we read about the work of international award-winning architect Nader Khalili. Nader is an Iranian-born architect who abandoned a successful career designing skyscrapers to follow his heart, which led him to create an innovative sandbag/superadobe/earthbag architecture as a means of providing low-tech, enduring affordable housing. Inspired by the ingenious monolithic adobe buildings of his homeland of Iran, Nader conceived the idea of building domed and vaulted structures with…bags of earth. We took a one-day workshop with Nader and we were hooked! We returned home excited to build our first earthbag-wall project, a privacy wall opposite the busy baseball field across from our house. However, our interest quickly zeroed in on the building process itself. We began innovating tools, tricks, and techniques that we felt made the building process more enjoyable and the results cleaner and predictably solid. We coined the acronym FQSS which stands for Fun, Quick, Simple and Solid. The process has to be Fun, which makes the work go Quickly as long as the procedure is kept Simple and the end results are Solid. Hence the FQSS stamp of approval became our dirtbag golden guideline.

Earthbags (as we were soon to discover) had the advantage of being able to use a wider range of soil types than traditional earth building techniques – “Wow, this dirt’s just got five percent clay and it still works!” We have been able to adapt soils for use in earthbags that have ranged from zero clay to 50 percent clay content. No type of fiber was needed within the soil. Since the bag acts as a textile container for the earth, the woven fibers do the job of stabilizing the soil in place so the soil can have a lesser quality binding strength than required for most other types of earthen construction. When necessary, even dry sand can be used as fill, as could be the case in providing emergency relief shelter. The Earthbag System is a contemporary form of earthen construction that uses modern woven polypropylene feedbags (usually misprints) or long tubes as a flexible textile container (or what we call a flexible form) preferably filled with dampened soil. The bags or tubes are filled in place on the wall being built so there is no heavy lifting. After a whole row is laid, the bags are compacted from above with hand tampers. The compacted earth later cures to a cement-like hardness. Two strands of four-point barbed wire are laid in between every row that act as a “Velcro” hook-and-latch mortar, cinching the bags together while providing continuous built-in tensile strength. Tensile strength inhibits the walls from being pulled apart during stressful conditions like earthquakes, floods, hurricanes, and load-bearing and lateral forces. The combined strength of the four-point barbed wire sandwiched in between the woven textile fabric of every row of earthbags adds a significant degree of tensile resilience that is lacking in most traditional forms of earthen architecture.

earthbag3-240x300The soil we selected for our initial earthbag building projects was delivered from our local gravel yard at 80 cents per ton. That was ten years ago. Today we pay about $1.80 per ton. Reject sand or crusher fines are common names for the clay fines that are the byproduct from the manufacture of washed sand and gravel produced at most developed gravel yards. Often, this reject material has sufficient clay-to-sand ratio to produce strong compacted earthen blocks. However, over the years, we have had considerable success with using almost any type of soil available on site by paying particular attention to adjusting the moisture-to-soil ratio that produces the optimal strength block.

Building the earthbags around temporary rigid box and arch forms creates door and window openings. After compaction of the keystone bags, the forms are then removed. Wood-strip anchors are installed during the wall-building process, providing an attachment for bolting on doorjambs, cabinetry or wood-frame intersecting walls, electrical outlets and plumbing systems.

Wall plastering options range from thick natural earthen plaster applied directly over the surface of the bags (yes, it sticks!) or, for additional protection, lime plaster can be applied over an earthen plaster. Cement/lime based plasters perform well when the earthbags are filled with a stable, well-draining sandy soil and applied over stucco mesh (chicken wire). Plasters can be applied by hand or sprayed on with a pressurized plaster sprayer for a unique contoured effect that accents the shape of the bags or tubes.

Earthbag Architecture can be designed to suit a wide variety of climates. Since the woven polypropylene bags are virtually rot proof, earthbags are an excellent choice for underground structures: root cellars, storm shelters, bermed homes and greenhouses. In climates where wood is scarce, whole houses can be built exclusively with earthbags including the foundation and roof, as is the case for corbelled earthbag domes. Earthbags also combine well with other natural building materials that can be combined together to create hybrid structures. Straw bales can be interlocked with earthbags to build sturdy arch entryways or to add thermal mass to the interior wall of an attached sunroom. Or we may choose to use earthbags for the sunken first level of a structure and then switch to strawbale, post-andbeam, cob or adobe brick for the rest of the wall above grade to make use of an available resource or add aesthetic variety.

The advantage of combining two alternative natural building mediums: load-bearing earthbag walls provide mega-thermal mass, while an exterior straw-bale wrap provides mega-insulation.

The advantage of combining two alternative natural building mediums: load-bearing earthbag walls provide mega-thermal mass, while an exterior straw-bale wrap provides mega-insulation.

Insulation strategies for earthbag walls offer a variety of options. Narrow tubes provide a sturdy load-bearing wall with plenty of thermal mass, while straw bales secured to the exterior of the wall provide ample insulation. Now, we have mega mass coupled with mega insulation to provide the best use of both of these materials in one building. Another way to add interior mass is to build our interior walls with earthbags and our exterior walls with straw bales alone. Another approach we have experimented with is mixing a percentage of 3/4-inch pumice to a quality rammed earth soil that captures air spaces within the earthbag itself. A 50/50 mix of suitable earth and pumice make the bags one third lighter than their normal all dirt weight yet still makes a nice hard compacted earthbag.

Building codes

The advantage of combining two alternative natural building mediums: load-bearing earthbag walls provide mega-thermal mass, while an exterior straw-bale wrap
provides mega-insulation.

The earthbag building system has been extensively tested by Nader Khalili in conjunction with the ICBO (International Conference of Building Inspectors) and the Hesperia Building Department in Hesperia, California, at the California Institute of Earth Art and Architecture for earthquake resilience, loadbearing, and shear strength stability, all of which were proven to far exceed conventional code standard acceptance. (See Building Standards issue Sandbag/Superadobe/ Superblock Sept-Oct 1998 for a full article on the merits of Earthbag structural nitty-gritty).

Resources

Sources for bags and tubes can be found on the Internet under woven polypropylene feed bags. Our favorite U.S. supplier for both pillow-pack and gusseted misprint bags is www.innpack.com, toll-free 800.622.3695 in Tennessee. Typical prices for 50-lb misprints are approximately $.17 each (USD), and 100-lb bags are $.25 each (USD). Both come in bales of 1,000 bags. Smaller quantities for bags and tubes are available from a Kansas City, Missouri, source www.centralbagcompany.com 816.471.0388. Ask for Chris Klimek for prices and selection. Also try 800.521.1414 www.fultonpacific.com.

For step-by-step nitpicking details about building with earthbags, check out our book Earthbag Building, the Tools Tricks and Techniques by Kaki Hunter and Donald Kiffmeyer, New Society Publishers, 2004. Or call us at 435.259.8378, or visit our web site www.okokok.org.

Donald Kiffmeyer and Kaki Hunter have been involved in alternative construction since 1993, specializing in affordable, low impact and natural building methods. Inspired by the work of visionary architect Nader Khalili, the grandfather of Sandbag/ Superadobe/Earthbag architecture, they wrote a screenplay entitled “Honey’s House,” a film about truth, justice and affordable housing. From these innocent beginnings, they were launched into the alternative building movement where they were encouraged to share their combined innovations to establish the Flexible Form Rammed Earth technique. Together they co-authored the book Earthbag Building, the Tools, Tricks and Techniques by New Society Publishers. They live in Moab, Utah, where they continue to focus on the research and development of fun, quick, simple and solid natural and alternative building techniques that are inspired by this fabulous planet.

Panel-built Classroom in Northern Arizona

By Bales, Design, Products, Walls No Comments

This article originally appeared in TLS #49.  Articles on straw-bale wall panel systems are included in issues #30, #42, #47, #48, #55.

panels1-300x224by Matt Robinson – Arizona, USA

Northen Arizona provides an ideal climate in which to build with straw bales and has been the site of many such structures since the 1990s. Ed Dunn has been the principal designer and builder of straw-bale homes here for over a decade. In May‘04, Western Strawbale Builders (WSB) was formed by Jason Radosevich and Matt Robinson, former crew members of Ed Dunn. The focus of WSB is to increase the scope of straw-bale building to include affordable housing as well as top-of-the-line custom housing.

With affordability in mind, systems using prefab panels seem to us the most promising avenue of approach to building with straw bales. In order to spare you the well covered details of this method of building, you can reference several articles published by TLS including: Chris Magwood in TLS#42, Canada Guy TLS#47, and Brett KenCairn in TLS#48.

Western Strawbale Builders was able to show off our skills in a project this past Fall here in Northern AZ. Designed and overseen by Ed Dunn, this project was an additional building done for The Star School, an off-grid solar-powered charter school on the borders of the Navajo Reservation in Coconino County. Star School teaches middle school students subjects, including permaculture, cultural awareness, and sustainability. Proprietors Mark and Kate Sorrenson therefore wanted to build a structure that reflected these values while fitting into their budget.

Ed Dunn designed this structure to utilize passive solar principles, trombe walls and a greywater planter. It is to be used as a combination classroom, performance hall, and wrestling gym, as well as any other creative uses Mark and Kate come up with.

We decided to hold the bid on this project to the regular bid price for stick-framed structures in our area to see how well we could compete. To our mild shock and great relief, we were able to build to these numbers and still afford our business a modest profit. With a four-man crew including ourselves and the exceptional abilities of carpenters Alden Catherman and Phil Mason, the class room was completed in eight workweeks, beginning to end.

We feel that this project, although relatively simple in scale and design, can serve as an example of an affordable option for people who love the idea and feel of straw-built houses. Hopefully this structure and others like it will help in bringing straw-bale houses into the mainstream.

Matt Robinson and Jason Radosevich own and operate Western Strawbale Builders in Flagstaff, AZ. Contact: or westernstrawbale.com

A Bit About Bale Walls

By Bales, Straw Bale Construction, Walls No Comments

Currently in rough draft form, this information is the beginning preparation for an article or perhaps two that will appear in a future issue of The Last Straw journal with the theme “All About Bales.” Your comments and input are welcome.

by Joyce Coppinger, Managing Editor/Publisher, The Last Straw Journal

Wall Structures
The structural methods used for the design and construction of bale walls are generally of two types: loadbearing and non-loadbearing. Stated another way – bales supporting the weight of the roof and any snow or other roof loads, and any post-and-beam or modified post-and-beam structure with the bales used as infill for insulation only.

Timberframe is the post-and-beam structure of choice in most countries. Posts of conventional milled 4×4, 4×6 and 6×6 wood; lodge poles, timber bamboo and other types of materials have been used. Modified post-and-beam structures are wide-ranging and diverse – anything from box columns to ladder-truss wall systems, to the current experiments in and development of SIP or structural insulated wall systems (also called wall panel systems or panelized walls) using bales as the insulation material rather than rigid foam insulation as the material sandwiched between the sheathing on both sides. [See articles in TLS#42 and #55.]

Widths
Bale walls come in many different widths depending on the size of bales you use, how you lay the bales as you stack them, and even the type of material baled and the method used to stack the bales to form the wall.

Widths Using Small Square Bales: Typical widths for bale walls are 16 or 18 inches when the bales are laid flat (strings or wires on the top of the bale). If stacked on edge, the bale width will be 14 inches with the strings or wires on the side of the bale. If the bale is stood on end to fill a framed space, the bale can be either 14, 16 or 18 inches depending on the size of the bale and the direction in which you set the bale.

Size of Bales
Even though a bale may be called “square,” it’s usually rectangular in shape.

The size of a small square bale may vary by region or country depending on the type of baling equipment used or the method of making the bale, e.g., bale press or hand pressed compared to using a mechanical baler. The bale may also vary because of the type of mechanical baler used and how it’s set to produce a bale.

The small and medium size balers used in some regions of the U.S. have a fixed bale chamber that produces a bale that is 14-in.x16-in., 14-in.x18-in. or 16-in.x18-in. The length can be varied to produce bales between 36 inches and 41 to 48 inches. This is the range of length that is required by most automatic bale wagons used to pick up bales in the field in the U.S..

You should also be aware that there are also other sizes of bales used – some are called “jumbo” bales because of their large size. In some places, these large bales might be called 4x4s or 6x6s or 8x8s. Some people define a square bale’s size as small, medium and large. Small bales can be 24in.x24in.x48-in. Or they can be 14-in.x 16 to 18 in.x 36 to 48 in. A medium bale of this type is around 4-ft.x4-ft.x6-ft., and large bales around 6-ft. to 8-ft. square by 8-ft. to 10-ft. long. Weight depends on the type of hay and settings of the baling equipment.

And density (compactness of the baled material) or compression (how much pressure is placed on the bales to “compress” them when they are created or after they are stacked) of the bales might also change the dimensions.

The binding material on the bales is most often wire or poly twine; sisal (natural fiber) isn’t the best to use as it tends to break while the bales are being handled. Some people don’t use wire as they are concerned about moisture might condense on it or be drawn to it; some feel it’s difficult to work with when retying bales, others feel it’s easier. Some don’t like to use the poly twine because of the coating or because they feel it’s not as easy to work with. In most cases ot comes down to personal preference or type of binding available locally.

Placement of Bales
Bales laid flat are usually 16 to 18 inches wide and 14 inches high; they can be 36 to 40 to 48 inches long. Bales stacked on edge are usually 14 inches wide, 16 to 18 inches high, and the same lengths as mentioned for bales laid flat. Bales used to fill in framed spaces – or stacked on end – can be 14, 16 or 18 inches wide depending on how you orient the bale in the space filled.

There has been and continues to be much discussion about the way bales are laid or positioned when stacked. Are bales set on edge or bales laid flat easier to plaster, and what reasons do balers use to explain a preference for one method or the other? Do the bales laid flat have less or ore insulation value – and why?  Do bales set on edge have more tensile strength than bales laid flat?

What to Use and What Not to Use
A bale made with a mechanical baler that chops the straw as the bales are made probably doesn’t produce the best bale for construction – it tends to fall apart or could be harder to work with when cutting and tying.

A bale made from alfalfa will be hard to use – the alfalfa tends to be woody and brittle, the bales are usually not uniform in shape and perhaps even in size to some extent. This may be true of bales made from switchgrass or flax or other “slippery” materials.

Bales made from tumbleweeds are not suitable for bale building – they are very brittle and highly flammable (usually very dry). The same could be said for pine straw bales – the kerosene in the pine needles is flammable and the pine needles are also one of those “slippery” materials mentioned earlier.

The most common materials used for buildable bales are wheat, oats, rye, rice, and hemp. It’s said that the Nebraska prairie pioneers used prairie meadow hay (probably hard to find these days), cattails and wetland reeds (most often baled during droughts). We’ve heard of the use of bales made with timothy grass, Sudan grass, and barley. We’ve been asked about corn stover and soybean stover – but don’t know of anyone who’s ever used this crop residue as a bale building material. If you’ve heard of other materials used for buildable bales, please let TLS know.

Fire in a House With Straw Bale Walls

By Fire, Straw Bale Construction, Walls One Comment

This article is original content and has not yet appeared in the printed version of The Last Straw.

No, this is not the house.  We dont have a picture of a bale house on fire!

No, this is not the house. We don’t have a picture of a bale house on fire!

This story is a reluctant one about a house comprised of both wood-framed and straw bale walls lost to a fire in 2009. The structure was built over a longer period of time than most main-stream homes.  The different phases incorporated the most appropriate materials at the time for the owners. We are excluding specific reference to the owners and the location of the building due to privacy concerns. For this article we will say that the building is in the central U.S. at approximately 8,000 ft elevation and the Owner’s name is Bob. In the end, it really does not matter who owns the home or exactly where it is. What we will focus on is the performance of the bale walls in the fire, the aftermath, and how the owners and insurance company feels about the whole incident.

The building was an un-permitted residence in a rural mountainous area. As mentioned above, some of the walls were wood-framed, others were built with bales. The bale portion of the structure was round, approximately 26′ in diameter, on a foundation that was an 8″x18″ concrete grade-beam supported by concrete pillars, with a yurt-style roof which included a “tension-ring” cable. The bale walls were Nebraska-Style (no posts) and had a 2×6 box-beam for the top plate with plywood on the bottom but not the top. The box-beam was filled with rigid foam insulation. Both the interior and exterior surfaces of the bale walls were covered with cement-based plaster. Two coats were present on the exterior and one coat was completed on the interior. There were relatively small areas not plastered on the interior, but the location of these un-plastered areas were not specified in my conversation with Bob.

The fire was started in the crawl-space of the framed portion of the structure by accident. It quickly spread throughout the framed structure and overtook the occupants who had to flee for their safety.  Bob is a local volunteer firefighter who was overcome with smoke inhalation and had to be taken away for medical care. He was present for a majority of the fire and taken away before it was extinguished. However, he has some interesting comments regarding the bale walls, how they performed and how they were affected by the fire. The family lost everything to the fire and is now picking through the remains.

The fire quickly engulfed all of the wood-framed structure and spread to the floor and then the roof of the round bale structure. The roof of the round structure collapsed inside the bale walls but the bale walls themselves were still standing when the fire department , hampered by by the long driveway and 18″ of fresh snow, arrived on the scene 50 minutes after the fire started.   Due to smoldering straw the fire department felt compelled to knock the bale walls down to access smoldering area within the walls.  Eventually all the bale walls were knocked down and all of the smoldering extinguished. This process took five days after the initial incident.

Bob commented about how fast the areas with no plaster ignited compared to the bale walls covered with plaster. The windows and doors had been framed using standard wood bucks. These, in addition to the wood box-beam, became the main avenues for the fire to spread into the bale walls. It appeared that the fire moved down from the top and in from the window and door bucks. Had these areas been plastered, or concrete bucks used, Bob feels the bale walls may have been spared.

Due to the generally impenetrable nature of the walls they seemed to act as barriers to heat-flow in both beneficial and detrimental ways.  Bob had installed his solar PV array 10 feet from the bale structure. The PV panels were virtually unharmed due to the shielding nature of the bale walls. His wood-framed shop, situated approximately 30 feet from the framed portion of the residence, ended up burning to the ground from direct exposure to the heat of the fire. The drawback was that Bob felt the bale walls created an oven-like effect within the building, holding heat inside, keeping the temperature very high.  As a result, one of the losses was the family safe which was supposedly fire-proof.  It was unable to withstand the “heat-trap” surrounded and created by the bale walls.  From these accounts, It is clear that the bale walls have a very significant heat-shielding effect during a major fire event.

The entire structure was insured by Allstate Insurance.  Bob was honest with them at the time of insuring the building and did not hide the fact that part of the building incorporated bale walls.  Allstate did not seem to make a big deal of the fact either then or now.  It appears they are making a pay-out on the insurance policy.  This is good news to bale building owners everywhere.  An insurance company had the capacity to not focus on the fact that some of the exterior walls were made of straw and plaster.  It is not clear if they understood how stable the walls were during the fire since they did not collapse, like the rest of the structure.  The fact that the bale walls did not contribute to serious problems was probably one reason for the lack of focus.

Being a volunteer firefighter Bob was frustrated he could not help fight the fire that destroyed his own home.  He understood that following orders from his fellow firefighters to seek help for his smoke inhalation was the right thing to do.  When asked about how the fire was suppressed in the bale walls and why it took so long, it became clear that the ongoing smoldering was not going to stop on it’s own.  The walls needed to be broken up in order to access all of the smoldering spots.

It seems that there is a pattern among bale buildings that are engulfed by flames.  The walls remain standing as long as anyone is willing to let them stand.  The main reason they are taken down is to gain access to smoldering areas within the walls so as to eliminate any risk of spread and the accidental ignition of other fires elsewhere.  The fact that bale walls are very effective heat shields makes them good fire-separation wall candidates between living units, or uses, within a structure.  They remain stable throughout the fire event, which cannot be said of steel or wood-framed walls in low-rise residential or commercial construction.  The fact that they tend to smolder and require maintenance for days after the initial fire event costs money and resources, but weighed against the fact that they do not fail catastrophically means that they may be considered as life-safety elements in buildings with many uses and occupancies.

The lessons learned in this building are that bale walls are incredibly stable during a fire event, offer a thick shield to retard flame-spread, and are tough to dismantle, requiring many days and resources by the local fire department.  When put together it seems that the bale walls themselves had a much better track record than any other part of the structure.  Feel free to comment or add to the discussion by logging in and submitting your thoughts.

Bob says he will not rebuild with bales mainly due to the huge amount of labor involved.  He will probably choose to build with some form of ICF (insulated concrete form) and steel.  He and his family enjoyed their bale home, but the time and labor necessary do not seem as realistic the second time around.

All fires in bale buildings are felt throughout the community as a serious and deep loss.  Even though we do not wish for them there is a great deal to learn from each and every one.  We hope this account will help firefighters, insurers, designers and homeowners make the best decisions possible.  Please comment below and participate in the conversation.  We are interested in your thoughts.  Email the author with any specific question for the owner offline.