Straw bales currently come in come in three sizes: small, two wire; medium, three wire; and large round bales. The medium is the preferred size at 23″x16″x42″ and weighing 75-85 pounds. These also have the highest R-value, around R-50.

There are five recognized methods of building with straw bales:

1. In-Fill or Non-Structural — This method depends on some sort of pole or post-and-beam framing. Obviously the framing is then filled in with straw bales. It’s particularly useful for large buildings.
2. Structural — With this method, bales are stacked up like bricks up to one and a half stories. Some sort of spike is driven through the bales to hold them in place.
3. Straw-Clay Building — A clay and water mixture is stirred into loose stray and then packed into ladder-like frames. This makes for an extremely strong wall.
4. Mortar — In this method, structural mortar is placed between bales. Even if the bales eventually give way, one source says that the lattice of mortar will remain.
5. Pressed Straw — Straw is compacted under a certain temperature which results in 100% straw panels. These can be used fro prefabricated structures and even roofs.

In all the methods the outside is stuccoed (rendered) with earth or lime to protect it from the elements. The inside is plastered.

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Building with straw bales has been around for hundreds of years, but it has recently gained more momentum as a result of declining timber sources. Because it is readily available in so many areas it is very inexpensive. The USDA estimates that enough straw is harvested by farmers every year to build four million 2,000 square foot homes; clearly this is an underutilized building material.

There are three common mis-conceptions and apprehensions when you begin to talk about straw bale construction:

1. that straw bales are a fire hazard.
2. that straw bales house rodents.
3. and that straw bales are not structurally sound.

I’ll just jump right in. Straw bale houses are not a fire hazard. Studies have proven unrendered (not stuccoed or plastered) walls to be less of a fire risk than timber walls, and rendered walls are just a fire resistant as bricks. Rodents will not be attracted to straw bales for food, but they do like the holes. If the house is properly maintained there should be no problem whatsoever with mice and rats. As for straw bale homes not being structurally sound, that’s obviously not true. There are houses with this construction a hundred years old and older, and, with modern technology, there is no reason in the world why straw bale houses built today shouldn’t last just as long or longer.
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