The thick walls of a straw-bale wall have become synonymous with the green building movement. Part low-tech technique, part clever use of a waste material, straw bale is an attractive and popular alternative to wood framing.
Stories of the first use of straw bale date back to the 1890s when settlers in the Midwest plains of Nebraska had to make do with what was available. Trees were scarce. Because straw bale is really just a waste product, a leftover from their normal farming activities, the farmers had to find a use for it. Several of these buildings are still standing today.

 The use of straw bale slowed after World War II due to the surplus of other building materials. Early hobbyist homebuilders started tinkering around with straw bale again in the 1970s in response to the energy crisis. This natural, nontoxic, renewable, and abundant material was quickly embraced by green builders.

What Straw Bale Is

When wheat and rice farmers strip off the husks of the plant during a harvest, long, hollow stalks of straw are left behind. A large machine, called a baler, packs this straw into large bricks called straw bales. Bales can come from the harvesting of wheat, oats, barley, rice, rye, or flax.

The bales I’m talking about are straw, not hay. If you were to use hay, it would attract insects. The strong fibers of straw are pure cellulose (the same material as your fingernails) and contain nothing for the insects to eat.

Measuring around 14 inches wide, 18 inches tall, and 36 inches long, the tightly packed bales of straw weigh about 50 to 60 pounds each — just light enough for a strong person to stack into a wall.

Some 200 million tons of straw are wasted each year in the United States. The annual straw harvest in the United States could build around 4 million average-size homes every year. That’s four times the number of houses built each year!

When you hear about a straw house, you may be thinking of something out of the Three Little Pigs. But as you can see below, the bales are piled up like bricks and cannot be blown down, not even by a big bad wolf. Bamboo stakes or steel reinforcing bars (rebar) are used between each row to pin the bales together. Unlike real bricks, mortar is not used between the bales.

After the bales are all stacked up, plumbing and electrical conduits are easily placed in the wall. At the door and window locations, wood is used around the straw bale to act as a place to screw the door and window frames to the wall.

After the wall is completed, it has to be finished with something to keep the water out. Natural mud-based or lime-based stucco is traditionally used on the outside, with breathable earthen plaster on the inside. The stucco will not stick to the straw by itself, so a wire mesh (called metal lath or chicken wire) is wrapped over the straw to hold the finish.

The roof is set over the walls and is typically made of wood joists or trusses, just like on a wood-frame home.  ....read more