Originally published on July 29, 2019
Author Kelly Hart
Today is the Build portion of our Grow Make Build Change summer reading sale theme featuring an excerpt from Essential Earthbag Construction: The Complete Step-by-Step Guide by Kelly Hart. Earthbag construction — building with polypropylene bags usually
— is a versatile, easy-to-master, low-impact, and highly durable form of building, suitable for structures from houses to root cellars. Today's post highlights some of the pros and cons of working with earthbags. You can download the full chapter here.
Excerpt from the Introduction
Earthbag construction is remarkably versatile, perhaps more than any other building technique. It can be employed both above and below ground without concern for rot or degradation. It can create thermal mass or an insulating barrier, depending on what the bags are filled with. It can be fashioned into a wide range of building shapes, from organically curvy to completely rectilinear, from domes to boxes — or combinations of any of these. It can be extremely durable, resisting fire, flood, earthquake, tornado, bullets, and time. It can also be quite economical — literally, dirt cheap.
The techniques are simple to learn; for the most part, the work can be done by unskilled labor.
The building shells are generally nontoxic, made of natural materials that can be returned to the earth or recycled at the end of their useful life.
Often, very little wood or industrial materials are needed, so the buildings are environmentally benign. A simple rubble trench foundation may be all that is required, eliminating the need for massive concrete foundations. Besides buildings, earthbags can be used to build dams, cisterns, retaining walls, and other landscaping features. What more could you want?
Authors home under construction
Of course, all of the above considerations depend on good design and proper execution for good results. As with any building method, it is essential to be educated about proper design principles and procedures before embarking on any project. This book will give you not only a better understanding of the technique of building with earthbags, it will give you all the information you need to actually do it.
Earthbag walls are usually rather thick and heavy, which does limit some of their possible uses. For instance, they may not be the best choice for interior walls, where space may be limited; they are not a good choice where plumbing or electrical needs to be run, or where there isn’t an adequate foundation to support the weight.
In most climates around the world, it is best for the shell of a habitable building to be insulated from the extremes of ambient temperatures in order to have a comfortable and energy-efficient dwelling. Unfortunately, most soils are poor insulators, so filling earthbags with soil has limited utility. To remedy this, it is possible to either fill the bags with a more insulating material or to add a secondary insulating layer on the outside of the shell. Lightweight volcanic stone (such as scoria or pumice), perlite, vermiculite, and rice hulls are all insulating materials that can be used for fill. These materials are not available in all localities, or they might be too expensive for a given project. When investigating the possibility of building with earthbags, the availability of the most appropriate fill material needs to be a primary consideration.
A general problem with earthbag building is that you may have to jump through some extra hoops to obtain a building permit — if one is required. Earthbag technology is simply too new and too alternative to have generated the necessary impetus for uniform codes to have been adopted. This means that in order to be acceptable to the authorities, any given plan may need to be signed by a licensed engineer or architect who will vouch for its safety, and this can add to the time and expense of a project.