Straw bale construction has been around for a long time. It is a construction method that uses straw bales from wheat, barley, rye, oats, and rice among others as walls and then covered with stucco; it has been used since the Paleolithic in Africa; some homes built in Nebraska, USA from the early 1900’s are still standing. Straw bales are staggered pretty much as bricks and depending on where one lives the structure should be designed accordingly. This type of construction has been recently revived by eco-enthusiasts everywhere. It indeed offers great features:
- It uses a byproduct that is renewable such as waste straw that otherwise would be tilled back or burned in open fields, releasing CO2 back to the atmosphere and hazardous breathable dust.The following is some basic info about the construction process:
- Depending on your location straw may be readily available; if you live in a state where any of these crops are harvested then it’s easy an inexpensive to have then dropped off at your construction site.
- Straw walls offer great sound proofing to the home.
- They provide excellent insulation, thus they are energy efficient.
- They are easy to build and inexpensive compared to conventional construction methods. Although, we have to keep in mind that expenses get higher the further the straw needs to travel.
- Depending on the design, walls can act as bearing walls and the roof could rest directly on top of them.
- Homes can be designed to be organic and rustic or modern with clean straight lines.
- Straw is rich in hard cellulose (75%) –and wood lignin (17%)-making it non edible for bug pests or any other animal for that matter, it takes four stomachs in a cow to get it digested!
Before construction; straw bales must be allowed to dry out sufficiently. It is a basic requirement for the bales to have a maximum of 15% moisture to avoid any future rot. A moisture meter should be used to determine the moisture trough every bale. During construction is important to install moisture barriers wherever it’s needed and the first row of bales should begin over a raised footing or foundation. When cutting or notching the bales must be retied and packed tightly. For a know-how instructional video visit: http://youtu.be/4y6Wpd0vGj4 where you’ll see how the knots are done.
As mentioned before; the structure will greatly depend on where on lives and construction codes. In some cases rebar or bamboo shafts are inserted through the bales to make the wall sturdier and stronger. Different types of stucco can be used. Cement stucco is the longest lasting and should be applied over mesh wire lath attached to the bales. The wire mesh will help in keeping everything in place; give the stucco something to grip on and overall making a stronger construction. There is also the option of earthen stucco, check out the properties of the soil in your job site area as this could be used in a mix to cover the walls giving them a very nice adobe color.
I found an interesting website where they say that The University of Western Ontario is doing some research about processing rice straw in to a concrete mixture. Rice straw is rich in silica which enhances the strength and durability of concrete. As a result of the process steam and Potassium are produced. The generated steam is converted to electricity and the excess goes to the grid. Then the Potassium is used as fertilizer in the agricultural industry. Read more about this topic at:
www.worldiscoveries.ca/technology/304
www.worldiscoveries.ca/technology/304
