Building with Straw

by Chuck Hall

In spite of any childhood stories you may have heard about the Three Little Pigs, homes made of straw are actually quite comfortable, affordable and safe. Straw has the added advantage of being highly sustainable. The types of straw used in straw bale construction are by-products of grain harvesting. Straw that would otherwise be used for animal bedding, landscaping, or just for kindling can also be used to build homes. Straw is also an annual crop, unlike lumber, which can take several decades to replenish.

Building with straw was used in the plains of the United States way back in the 1800s. Some of those structures are still standing as a testimonial to the durability of this building technique.

Straw bale buildings are made by stacking bales of straw inside a framework. A stone or masonry footer is built first to keep the straw dry by preventing contact with the ground. The framework supports the roof and adds stability to the structure. It can be made of wood or metal. Openings for windows and doors can easily be cut using a chainsaw. Once the straw bale walls are in place, they are finished with a coat of plaster. Concrete stucco is not recommended, as it doesn’t allow the walls to breathe. Moisture can potentially accumulate inside the straw, and it needs a way to escape so that the straw does not mildew. It is therefore recommended that you use an earth or lime-based plaster to improve breatheability.

Amateurs with little or no experience can build straw bale homes. The finished result looks similar to adobe, and straw bale homes can be built very inexpensively. These homes have been built for as little as ten dollars per square foot. Additionally, straw has a very high insulating factor, estimated at between R-35 and R-45!

The first question people generally ask about building with straw is, “Isn’t it highly flammable?” While straw itself is flammable, once it is coated inside and out with plaster it is very safe. The plaster prevents the fire from getting into the walls from the outside, and should a spark find a way inside the wall, the plaster keeps the straw from getting enough oxygen to burn. When properly constructed, a straw bale home is at least as safe as a traditional stick-built home, and straw bale can be less expensive (if you don’t use a contractor and do it yourself) and more energy efficient.

The main factor to consider with straw bale construction is damage due to humidity. If moisture gets into the straw, it can cause mildew or water damage. So if you are building yourself, take extra precautions to limit moisture within the walls. A good beginner’s guide to minimizing water damage in straw bale construction can be found at: www.skillful-means.com/strawbale/papers/moisture.htm.

For more general information on straw bale building, including a directory of homes built with straw, visit the Green Builder’s Straw Bale Construction site at: www.greenbuilder.com/sourcebook/strawbale.html.