Jame Henderson of Henderson Clayworks shares his knowledge of bale wall plaster systems and how to differentiate the most important aspects of each
By Ryan Chivers
With the modern development of natural building technologies, there has been a resurgence and rediscovery of ancient and traditional methods of plasterwork. For over 10,000 years, in nearly every culture, humans have used lime as an applied material that serves as both function and decoration. From the frescoes of the Italian Renaissance to the sculpted bas relief masks of the ancient Mayans, the chemistry, durability and elegant beauty of lime has, until modern times, been a staple of art and architecture the world over. In the twentieth century, builders have all but forgotten how to work with earth and lime based mortars, and plasters. Thanks to the efforts of passionate builders, craftspeople, architects and designers, and many within the natural building community, these old ways are being revived and put into practice once again. Collectively we are relearning how to successfully formulate and apply traditional plasters, using locally sourced materials and modern tools.
The rich and mysterious culture of Morocco offers one example of an ancient lime plaster art, nearly lost, which is now enjoying a rebirth – Tedelakt
We like to share this is the type of information because the context of lime plaster is so broad and interesting. It is important to keep in mind your goals when choosing materials. The information below creates a connection between two areas of lime plaster that are very important to understand before choosing a material for your project.
The Endeavour Centre has shared their process for making artificial hydraulic lime using locally available materials. The fact that they are able to source the materials close to home and create a consistent material using a simple process is what makes this tid-bit stand out.
In Issue #62 Michel Couvreux from Transmineral explained the various types of hydraulic lime and how to choose one that is appropriate for your project based on specifications. Natural hydraulic lime (NHL) is a naturally occurring material of high consistency that is very durable and easy to work with. In contrast, an artificial hydraulic lime (AHL) is created by blending materials to create similar set times and durability performance as a NHL. As Michel points out in his article, the consistency of AHL’s cannot be guaranteed and therefore quality control may suffer. However, if experimentation is possible and a level of risk can be tolerated, following a similar to process to what the Endeavour Centre has done can be useful and beneficial.
The point here is that you must educate yourself and experiment before committing to a new mixture of materials. Most importantly, you want your building to perform as expected.
Let us know how your experiments go by sending us an article so we can share it with everyone.
Reviewed by Jeff Ruppert
Earth 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.
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.
Traditional Korean homes generally have a timber frame with adobe or wattle and daub infill, though regional variations are found throughout the country.
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.
by Chris Magwood
The straw bale revival of the 1990s reintroduced builders to a pioneer building method that showed remarkable potential for building in a modern context. The nature of the basic components of a straw bale wall system – bales with plaster applied directly to bales – combined several obvious advantages over other wall systems while simultaneously raising some serious questions.
The advantages are familiar to TLS readers: low environmental impact, simplicity and well placed thermal mass. The serious questions and attempts to answer them were the lifeblood of TLS: What about moisture? Air tightness? Cold climates? Humid climates? Longevity of the straw in all these conditions?
There was a lot more going on in the construction world of the 1990s than the straw bale revival. The housing industry was recovering from multiple moisture-related disasters, many caused by overly airtight but under-ventilated homes and/or the use of un-vented “waterproof” exterior cladding systems. The research into these issues, among other factors, led to a rise in prominence of “building science” as a distinct engineering discipline. The straw bale revivalists were extremely lucky to have the attention of some of building science’s leading practitioners, in particular John Straube, who authored several key articles and studies about straw bale walls that were essential to answering the question of why bale walls were so resilient, despite some seemingly obvious moisture concerns.
Simply put, building science attempts to quantify the movement of heat and moisture through building assemblies and help designers and builders to make decisions that lead to structures that adequately deal with the moisture and temperature regimens of their particular climate and use.
By Michel Couvreux
Thanks to the hard work of a few, Natural Hydraulic Lime has become one of the materials of choice for restoration/preservation projects and natural building construction in the United States.
Suddenly realizing the great potential of NHLs in the US, and feeling the economic hardship abroad, several European manufacturers have begun to latch onto the path opened by Saint-Astier.
Unfortunately, all NHLs are not equal in performance and quality.