This article first appeared in The Owner Builder 196 August/September 2016. www.theownerbuilder.com.au
By Hannah Moloney
As we live on a steep slope we’ve had to build a lot of retaining walls in order to create functionality around access, water management and food production. We’ve used a range of techniques to do this including working with old car tires to build a big earthship-style retaining wall near our house.
Earthship construction is a building technique developed by American architect Mike Reynolds. He’s famous for using ‘rubbish’ and earth as building materials. We love his work. We chose to build an earthship-style wall as we had a small budget and a lot of excess subsoil left over from our initial earth works. We also knew we could get car tires for free from the local car yard who have to pay to get rid of them.
Check your soil
We hadn’t built one of these before, so we spent some time on YouTube learning how – there are plenty videos to watch. While it’s pretty easy, it’s also a lot of hard work. It would have been whole lot easier if we had heaps of people to help, one of those cool Wacker Packer tools and dry, gravelly soil instead of the wet and sticky clay subsoil we’ve got at our place.
This last tip is really important: the YouTube video we watched made it look like a walk in the park with dry, sandy soil in New Mexico. The builder just poured it into the tire and patted it down; in contrast we shoveled, packed, wacked and shoveled some more. It was a bit of a mission. But it’s an incredibly strong wall and used up much of our excess subsoil, for which we were grateful.
Plug, pat and pound
Starting out, we cleared the space, tacked some white geofabric to the bank to keep it from dropping crumbs and made a level pad to start laying tires. As we were almost on bedrock, we didn’t have to lay any sand or concrete for footings; we just leveled it off.
As soon as you start building up from your first tire, you have to find a way to plug the holes so the earth doesn’t just fall through. We had a pile of carpet tiles the previous owner had left under our house, which fitted perfectly, so we used them. We backfilled the area directly behind the tires with 20mm blue metal and agricultural pipe to guide excess water out of this area. In addition, drainage holes are also necessary, as you never want any water building up behind a retaining wall.
We went five tires high and angled them all slightly towards the back for structural integrity. An important thing to note is that if you go over one meter high for a retaining wall you need an engineer (in our region at least) to design and approve things, which can get complicated and expensive. Because of this, we didn’t exceed this limit – it might look taller below, but that’s because the earth around the wall had been excavated and the paving hadn’t been put down yet.
Plug the gaps
The next step involved plugging the holes between tires with subsoil. The best approach was to simply form balls of sticky soil, ‘peg it’ (throw it really hard) into the gaps and then pat it in to make sure it’s all bedded down. After that, we wrapped the whole wall in chicken wire. This is what the external renders ‘hang on’ and it helps create a smooth, level surface.
We chose concrete render instead of earth for two reasons: firstly, this wall is in the coldest, dampest area of the whole property so it needs to be able to handle long months of never seeing the sun and being constantly wet. Secondly, we’re not overly experienced with earth building, so we took the conservative approach.
The finishing touches
Recently we (as in, Anton) did the paving around this area using recycled bricks that were pulled up from our local town square. This was the final job to do before we painted the wall bright blue with a colorful patterned border.
Another nifty feature of our new wall is little steps leading up to our food gardens. The only downside to these steps is that our little daughter Frida Maria loves climbing them. When you’re not looking she’ll be up there in two seconds! We’re happy she has a great time there, but it’s just that the potential of falling onto the hard bricks below is a little too stressful for us. A little gate may be in order.
We’d love to see more people using recycled materials to build inside and outside their homes. The amount of ‘rubbish’ in our world is mind-boggling and when we look closer at so-called rubbish, you’ll notice that most of it could actually be re-purposed into a valuable resource. The possibilities are endless – we just have to pull our socks up and get creative!
*Just a quick note: car tires can have some leaching of chemicals, which we wouldn’t personally be comfortable putting near food gardens. So this wall isn’t near our growing beds. Everything downhill from it (the leaching will move with gravity) is all brick paving and house.
Hannah Moloney is the co-founder of Good Life Permaculture offering design and teaching centered around the concept of radical homemaking, placing home and community at the core in order to create a good life. www.goodlifepermaculture.com.au
This article first appeared in The Owner Builder 192 December 2015/ January 2016. www.theownerbuilder.com.au
By Maggi McKerron
Ten years ago I fell in love with a mountain. Mt Chiang Dao rises 2173 metres out of the forests of northern Thailand, its jungle covered peaks dressed in swirls of clouds. I leased a piece of land on a small hill facing the mountain. Under half a hectare, the land slopes down to a small rural Thai village under the mountain, clustered around the nationally famous Chiang Dao Cave.
Planning a B&B
I was approaching upper middle age and realised I needed to make some sort of plan for older age when my life might possibly slow down a little. This piece of land would be perfect for a B&B!
I did not have the money to develop the land, so I took off for the UK to make some. Although I am British, I was born in India and have always lived in Asia. Going to the UK to work was a challenging experience, as I had to learn to live in a western culture for the first time, at the age of 56.
While in the UK I took the opportunity to study natural building, beginning with an inspirational earthbag building workshop taught by Paulina Wojciechowska, author of the first book on earthbag building. Making a dome out of earthbags sold me on domes and round dwellings. I was determined to build round domes back in Thailand!
But using earth as the building material did not sit right with me. I am mildly asthmatic and need dry air and did not relish the thought of being enclosed in an earthen dome during six months of monsoon rains. I thought about rice husks. This is a product that no one wants. It takes ages to break down if added to compost, and is difficult to burn. It is also a desiccant, which means that it will draw moisture out of the atmosphere. Perfect!
After seven years in the UK I finally had enough money to return to Thailand. At least I hoped it was enough. There was no way I could calculate the costs of the buildings in any detail, as I did not really know how I was going to build my rice husk domes. I couldn’t find any information on the internet: no plans available, no books on building with rice husks. I worked out a financial guesstimate, which I finally reached in savings, and I bought a one way ticket back to Thailand.
My beautiful land was covered in towering brush and it was not until a team of machete wielding villagers cleared it that I discovered how steeply it sloped. What a challenge this was going to be!
I should mention here that where I was building, out in the scarcely populated countryside, planning permission, although preferred by the local council, was not an issue. In towns and cities I would have had to submit plans. My local council signed off the building after it was finished.
Beginning the build
Ready to begin my adventure, I posted on social media that I would welcome anyone who would like to help with the project, and people turned up. I hired some local day labourers from the village. We found the flattest area, at the top of the property, and one of the first steps was to prepare for a concrete base. I had been warned by locals that the termites were ferocious and there really was no alternative to concrete.
We marked out a circle 5.5 metres in diameter with some bamboo stakes. Then we got some tubing and filled it with water, and tried to find a level. No one believed what the water in the tubes was telling us, so I went and bought a spirit level. This confirmed the water’s message; there was still a big slope, even though compared with the rest of the land it looked practically flat. Leveling the area was our first task.
My very rough plan showed a concrete cap on the dome, as this was all I could think of to keep out the monsoon rain, so our next task was putting up six concrete posts to carry the weight of the concrete cap. Then the base of sub soil and stones went in, pounded flat
by enthusiastic volunteers, a trellis of bamboo for strengthening, a sheet of plastic as a damp proof membrane to stop moisture leaching upward, some sand and a final topping of concrete.
Now I needed to seriously consider the dome. I could not for the life of me work out how to construct it. Unlike earthbags, which are load bearing and could support a concrete cap, I was working with lightweight, not at all solid, bags of rice husks. I spent ages in hardware stores, second-hand wood shops and looking through books. I asked various local builders, but one after the other they shook their heads, mystified with the ideas of the crazy foreign lady.
At one point I decided to forget the dome and just build a hexagonal roof using the steel for conventional roof frames. One of the volunteers said: ‘But Maggi, your dream is a dome. You must follow your dream.’ So I thought again.
I found reinforced steel rods, rebar, bendable and long. I could buy quite thick pieces and long enough to go from one side of a dome to the other. First a piece of rebar was bent into a circle to go around the building, sitting on the top of the concrete posts. Then up went the rebar making the dome shape and we wired it onto the posts and horizontal rebar. Using different thicknesses of rebar and adding bamboo we made a dome shaped trellis.
The bamboo for the trellis in the dome came from bamboo poles we harvested from the land. These we cut and prepared and wove as needed. We used the same trellis idea for the walls, and our bags of rice husks would be attached to this frame. The whole thing looked like a giant bird cage!
The windows and doors were added as we built the bamboo trellis. This was complicated as the walls were going to be quite thick, so windows and doors needed frames to sit in. We learned as we went along. At no point in the building did we use any electrical tools – there was no electricity!
Rice husk walls
Filling in the walls came next. I found a place that sold second-hand polypropylene bags and had bought several hundred. Then I found a rice mill that agreed to fill the bags for me with their waste husks, 200 a week. These we had been collecting in preparation.
The first layer of bags was filled with gravel to guard against water and moisture damaging the walls, with a layer of sand on top of that, then the bags filled with rice husks. We experimented with different types of string, and different knots and found the method that worked best. They went up quickly and easily in a couple of days, and soon we were at the level where the curve of the dome began.
The bags were too big. They would be too unwieldy and heavy to attach. We had to empty them, refill them with less rice husks, then tie them up in the shape of a sausage. Our sausages were quite complicated to put up as we were attaching them to the inside of the dome to continue the inside line of the walls.
The dome looked wonderful! The next step was to put on the concrete cap. We used plastic sheet covered with chicken wire and put the concrete on top. We made deep overhangs to protect the walls.
The last step was the mud on the walls. It took a while to perfect our recipe as putting plaster on bags of rice husks is not the same as putting it onto earthbags or straw bales. The bags were not solid, so plaster had to be built up slowly in several layers until it was firm and strong. Then a final layer of lime plaster, followed by some decorations, and our dome was finished!
The big lesson I learned was never to put a concrete cap on a dome in the kind of climate found in Thailand. It cracked, and cracked again! But because the rice husks dry out so easily it has not caused any lasting problems. The second lesson was to attach the bags to the outside of the dome trellis. Much easier!
Three years have gone by since the beginning of the adventure. I have three domes and five roundhouses with thatched roofs. All the buildings with their thick walls of rice husks covered with earthen plaster are cool in summer and warm in winter. I have a beautiful home, made from three of the five metre roundhouses, joined by thatched walkways. My B&B is up and running. And every day and all day I can see my mountain. My dream has come true.
Maggi will be running a roundhouse building workshop in November 2017. See website for details: www.chiangdao-roundhouses.com
Links & resources
Sharing her adventures of living – and building – in Chiang Dao, northern Thailand.
Chiang Dao Roundhouses
Set on the side of a hill overlooking the spectacular Mt Chiang Dao, offering rice husk workshops and B&B accommodation.
Carole Crews leads us on a journey through the parts of our home made with earth and water, but also tells an important story along the way.
We review the first comprehensive how-to guide covering the topic of earthen floors. Find out why you should have it in your natural building library.
Reviewed by Jeff Ruppert
Making Better Buildings: A Comparative Guide to Sustainable Construction for Homeowners and Contractors by Chris Magwood will be released this Spring and promises to be one of the most valuable tools for the designer and builder who wants to understand how their choices of systems rank in terms of environmental impact, cost and acceptability. No other compilation gives such an in-depth review of the most widely used natural building techniques. Not only will you find the tried and true methods of straw bale and rammed earth construction, you will find alternatives you never knew existed.
Being a guide, this is not a how-to manual. It does not have pictures showing how to build alternatives to concrete foundations, for example. What this book does is ensures you are not missing something, and if you are you will easily find it and be able to compare it quickly to what you think is the best choice. The information on each system is objective and easily referenced. What is so impressive about this book is the list of systems it covers:
- Walls and Insulation
- Floor and roof structure
- Sheathing and cladding materials
- Roof sheathing
- Surface finishing materials
- Mechanical systems
- Water systems
- Wastewater systems
- Heating and cooling systems
- Electrical generation
As a designer of natural buildings I found the tables used for comparison very easy to glance through. I was able to discern the most valuable information quickly once I became familiar with the format. Comparing choices is easy and finding the characteristics that may keep one system or another from fitting into a project simple. The format forces you to think about each system using the same set of parameters, such as code acceptance, embodied energy, waste generated, costs, durability, etc.
But let’s not mince words when talking about green building. This book is clear – the current mainstream methods of making buildings sucks from an environmental point of view and no matter how certified they are, they just aren’t that green. The systems reviewed in this book address the most fundamental issues facing our society and the construction trades. Systems such as steel and concrete construction are not included due to the simple fact that both materials cause huge harm to our environment. There is no need to waste paper (or bandwidth) on the higher end of impact and societal costs when you are focusing on real solutions. If you are reading this book it means you are serious about considering real alternatives in this day and age of high impact buildings and “greenwashing.”
Chris Magwood continues to bring us fresh ideas and perspectives with this publication. We recommend it not only to the professional designer and builder, but also to owners who are serious about making better choices on their next project.
Making Better Buildings will be available in March for $39.95 USD and CAD from New Society Publishers. It is approximately 460 pages and will be available in both paperback and as an eBook.
Paperback ISBN: 978-0-86571-706-0; eISBN: 978-1-55092-515-9
Disclaimer: Chris Magwood has appeared as guest editor in past issues and submits articles regularly to The Last Straw.
This article was originally printed in Issue #52, 2005
by Tom Lander – New Mexico, USA
We have by no means mastered Earthen floors but have gained enough experience to have been hired this past building season to install two, adding to the ten we have worked on along with teaching another dozen or so here at LanderLand during our workshops.
Our current style is some times called a poured adobe floor. The term poured seems to come from the world of concrete floors but a better word might be placing. No matter what term or method, one needs to properly prepare the sub floor. We prep to within of 1/2 in./13mm of finished grade and then basically apply the final 1/2 in./13mm topcoat. Like any earthen application, one needs to know their material in regard to the clay content of the soil. Here in Kingston, New Mexico, our soil has close to a 30% clay content so it’s a dream to use.
We teach two mixes for floors, what we call our sand mix and the other a straw mix. The sand mix is made up of 1 part sifted clay soil and 4 parts course fill sand with the largest particles as large as 3/16 in./5mm. These large particle sizes mixed with finer aggregates keep the floor from shrinking, cracking, and add compaction strength, and are also easier to apply. The clay soil is more like the binder and filler. You need enough water to mix damp. You can add a small amount of 1/2 in./13mm chopped straw for the aesthetics but it’s not necessary.
Our straw mix is a variation of our basic earth plaster with added sand. 2 parts sifted clay soil, 2 1/2 parts course fill sand and 2 parts 1/2 in./13mm chopped straw. Start with 1 part water. This mix is harder to apply than the sand mix. The wetter the mixes the easier they are to apply but the moisture may cause shrinking and cracking.
Let’s move away from the mixes and talk a bit about prep work. The heart of a good strong crack-free earth floor is the base that it is applied on. This is true for almost any floor be it concrete, tile or wood. Earth floors are more like concrete in that they must be properly compacted, graded and screeded flat. For the inexperienced owner/builder, floor prep can be intimidating, again the compacted sub floor is the key.
Apply your fill materials in “lifts” of 1 in./25mm to 2 in./50mm and compact damp. A trick, if you have the time, is to flood these materials with the garden hose. You can rent noisy, smelly plate and foot compacters; some big floor jobs require this. I still would buy an 8 in. x 8 in./20cm x 20cm hand compactor. I’ve moved away from making a compactor from a steel pipe and welded plate or a coffee can filled with concrete. I recommend prepping your floor early in the building process so it has time to be compacted naturally from working on it; this also keeps your walls clean, assuming your floor is last in the construction process.
In addition to compacting, there are also possible moisture issues and, in some locations, soil gases like radon. These are issues you or the builder will need to address. Certainly it is difficult to write about floor prep and “build up” in a short article. There are so many variations and situations depending on your particular site and needs. I always recommend reading about conventional building materials and techniques and talking with builders in the area.
I’m a big fan of radiant heat and almost always add the pipe to my concrete slabs even if I am not going to heat the slab. Never know when someone might. Pex pipe is easiest with concrete slabs, the most efficient being an isolated slab where 1 in./25mm or 2 in./50mm foam lines the bottom and sides, (a thermal break) steel mesh is laid down and the pipe attached with zip ties. On small floors, I now use cattle panel fencing for my wire mesh rather then the traditional rolled mesh; it’s more expensive but for me so much easier to use. So, in my opinion, the best floor would be a 4 in./10cm thick, 3000 psi concrete slab with added fiber and PEX radiant heat pipe with a final 1/2 in./13mm earth top. Don’t forget your fly ash and control joints, concrete cracks. This of course is a mix of conventional and natural, not for the purest.
One 300 sf radiant earth floor we did had 9 in./230mm of pumice put down over the native rock soil as the insulated layer and then we brought in another 10 in./250mm of crusher fines (road base), sand, earth, no foam and no steel. This technique had it’s own challenges, where again experience and creativity help. What is interesting in this house is to notice the different “feel” to the radiant floors from the earthen side next to the conventional isolated foam 4 in./10cm concrete radiant floor in the adjacent room. They both work, the house is warm but the concrete feels hotter to the feet.
So now you have prepped your floor rock solid (like concrete, huh?) to within 1/2 in./13mm of finish height. You have also gone around all the walls and drawn a line at your finished height. A day or two in advance, you might need to go around and fill any holes, voids or low spots with a damp clay-sand mix, maybe even tamping a bit with your nice tamper. When dry you should be able to sweep up any loose debris.
It’s a good idea to mix up your material a day in advance. Now, do your math. Calculate your square footage then your cubic footage and add about 30%. If your room is 10 ft x 12 ft, then 10 ft x 12 ft equals 120 sf. Multiply this by 0.0416 to get cubic feet. (0.0416 is 1/24th of 12 in.) 120 x 0.0416 = 4.99 cubic feet.[ For metric calculation: 3m x 3.6m = 10.8m2. 10.8m2 x 13mm = 0.14m3]
Add 30% more material. 4.99 x 0.3 = 1.49 for a total of 6 1/2 cubic feet. We add 30 % due to the fact that we will be measuring our materials dry so there is air space. Once wetted and applied, the material gets compacted by the toweling process and we lose volume. You will need a container to store all this material. A simple tub can be made out of a frame of straw bales set on the ground and lined with plastic or a tarp. You can also buy large kids’ swimming pools. The color of your floor will be the color of your dried clay. You can add concrete liquid or powdered colorants. It is always a good idea to do a few 3 ft x 3ft.90cm x 90cm samples to test for shrink, cracking and color, also a good way to practice your applying techniques.
How to apply
Again one of those concepts that is best shown during a workshop training session than through trying to write about it, but here it goes. Ahead of time make up a few 1/2 in. x 1/2 in./13mm x 13mm screed sticks. These are also the thickness guides, four per person. Vary the lengths, 12 in. to 36 in./30cm to 90cm. Also make some wooden pool trowels out of the 1/2 in./13mm thick concrete wood floats from your building center; they cost around $3.00 USD each. Keep one square for corners.
Plan your route of attack so you will be able to work your way out of the room. Begin by setting down some pre-wetted wood sticks – trowel lengths apart, shovel down some material and start working in the material between the sticks. The trick is to make sure the material is compacted well, no voids. Do a few square feet leaving the sticks in place to run your trowel over thus establishing the thickness. Don’t spend a lot of time making it look good right now. Slide out the sticks, you now have a square groove that needs to be filled. First, take your trowel and press the sharp sides and ends down to form sort of a vee, now add small amounts of material in the vee and trowel it flat. Any voids or air pockets will leave a spot for cracking so compress well. The tendency is to put too much material in at one time; instead use a small amount frequently rather than large amounts all at once. Keep your guide sticks clean, wash frequently so as not to add buildup creating a thicker and uneven floor. As you progress along placing material and removing sticks, go back over the previous areas with your trowel to smooth and even out your floor as far as you can reach back over what you did. Sounds easy? Hopefully you worked this all out in your 3 ft x 3 ft (90cm x 90cm) test samples.
Sure looks good doesn’t it? You’re not done yet. More steps involved as the floor begins to dry. A word of caution about drying, it’s important to get even drying. If the sun shines in a window or door, these must be covered up. Air circulation helps to remove the moisture and speed up drying but again you need even flow.
Now it’s all about timing. On hot days/in hot climates, we find it best to apply the floor early in the morning so that hopefully by late afternoon or early evening we will be able to get back on the floor with kneeboards and steel pool trowels, or apply late in the day and hopefully you are back on it first thing in the morning. Miss this window of opportunity and your floor will be too hard to steel trowel. If you were so good applying the material with the wood floats and you are happy with the results, then one can skip hard troweling so your floor will be a little more course.
So your floor is drying, time to hard trowel on kneeboards – 3/4 in./20mm plywood, 18 in. to 24 in./45-60cm square or 2 in./50mm foam blue board works well. Make sure to wet your kneeboards, otherwise they stick and pull up your material. Almost like hard troweling a concrete slab. Steel troweling tightens up and flattens the surface. We use pool trowels and basically just go over the whole floor again, pushing hard with two hands in big sweeping motions.
Once your floor has completely dried, it’s time to seal and fill the floor with Linseed oil. We will address sealing in our next article.
Tom and Satomi Lander have been involved with natural building since 1993 and began teaching straw-bale building and earth plaster in 2003.
They can be reached at <[email protected]> www.LanderLand.com
Visit www.LanderLand.com for color images and earthen floor workshop information.
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
We 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.
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.
The 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.
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.
The advantage of combining two alternative natural building mediums: load-bearing earthbag walls provide mega-thermal mass, while an exterior straw-bale wrap
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).
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.
This is the second of a two-part article on creating a poured adobe or earth floor. See Earth Floor, TLS#52, for the first article describing how to prepare for and install a poured adobe floor.
By Tom Lander – New Mexico, USA
Now, weeks later after your floor is 100 percent dry, it’s time to seal and fill the floor with Linseed oil. Here in the South West our floors can dry in a matter of a few weeks but in humid climates error on the safe side.
Linseed oil. We prefer raw linseed oil, less petroleum additives then the common boiled linseed oil but the boiled works if you are not concerned about petroleum out gassing. Even raw linseed oil has carcinogenic warning labels. Ask for an MSDS sheet. Linseed oil is made from flax seed.
Citrus Solvent (thinner) or mineral spirits, again petroleum out gassing
We are still learning how to estimate coverage and quantity so I’m not sure how much material is needed for your size floor. Maybe buy 2 gallons each for starters; you can buy linseed oil in 5-gallon lots.
4” paintbrushes, natural bristle is always best but pricey
Electric hot plate or gas camp stove
Large pot or kettle
Approved vapor mask
Safety glasses or goggles
Fan for air circulation/expelling fumes if you feel this is necessary
Sweep or vacuum any loose debris and dust. You might want to do a light mopping or sponging. Give yourself time for the moisture to dry before applying the oil.
Heat the linseed oil to almost boiling (do not boil). We are just trying to heat the oil to aide in soaking, absorbing in. This must be done outside with caution, flammable. Another option is to pour the oil into a large deep baking pan, cover with a piece of glass and let it sit out in the sun. Leave an air gap. With either method start with a small batch to get the hang of heating and applying.
Transfer the oil into a suitable container. You can paint the material on or if you are quick, you can pour some onto the floor and swoosh it around with the brush. The only risk here is that you will not get an even distribution of material. Try it. Be consistent and watch how the floor is absorbing. If more than one person is applying, then you might get varying results but by the time you are done it shouldn’t matter. Use up your first small amount then decide how much more (a large batch) to heat for your next go at it. For reference keep track of how much material you use for each coat and offer this info to others.
The floor will soak up this first coat and there should not be any pooling of the oil on the surface. Plan your route of attack so you end up working yourself out the door, window or hallway. You should be able to go back to the start and do a second full strength coat right a way. Remember your shoes will be picking up dirt and dust from the outside so take steps to minimize this. There are disposable booties one can buy to cover their shoes.
What we are trying to do is seal the floor but think of it more like filling the floor. Filling all the little air voids between the sand and clay particles with oil.
The floor will dictate the timing and how much material. Watch how the material soaks in. You might be able to continue with more heated, thinned coats the same day, unless you are tired or sick from the fumes and not wearing a vapor mask.
The first two coats can be applied full strength. For the third and fourth coat combine 75% oil with 25% thinner, heat and apply. Watch the absorption, watch for pooling or puddling but also give the material some time to soak in; you just don’t want it to dry on the surface. Have a rag and thinner handy to wipe up any excess otherwise the material dries on the floor and becomes sticky. If this happens then it’s quite a job to use thinner and rags to clean the floor. Apply at least two coats of this first diluted mix.
Next is a 50% to 50% heated mix. Hopefully by now you have learned if pouring and brushing works for you (certainly faster) or just brushing or maybe it’s time now to just brush. Isn’t this fun learning as you go? Like all earthen materials, they tell you when and what to do, what’s the word? Experience.
Remember, oily rags and brushes are flammable so hang out to dry and do not leave a pile of rags unless it’s in the middle of a gravel driveway and you want to have some fun.
Sunny Side http://www.gillroys.com