Strawbale Construction Methods and Techniques
As a former member of an ecovillage, an offgrid sustainable housing development, I have worked in the construction of several different varieties of buildings using strawbale as a structural element, insulative material, or both. There are three basic techniques of strawbale construction that are widely used within ecovillages and other sustainable developments.
Strawbale Construction Method: Post-and Beam, or Timber Frame
One popular technique of strawbale construction is the post-and-beam, or timber frame structure. This building type uses wooden posts and beams to create a strong, steady frame. The sturdy frame of the building supports the weight of the roof, as well as other structural additions like lofts and second-stories.
After a wooden frame is installed, the walls are built using tight strawbale bricks as filling material. Although the strawbales act as an insulative material and provide some additional structural support, the bales themselves do not support the roof of the building.
Timber framed strawbale construction is ideal for large and multi-story strawbale buildings. Although it requires more work and financial investment than some of the alternatives, this construction style is believed to last longer and require less maintenence than load-bearing design.
Strawbale Construction Method: Load-Bearing, or Nebraska-Style
Dubbed “Nebraska Style” by ecovillagers and others who promote sustainable construction, load-bearing strawbale buildings are surprisingly easy to assemble. Aside from laying a foundation and building a roof–by far, the two hardest parts–the construction of a load-bearing strawbale house is as easy as stacking Legos.
Load-bearing strawbale buildings differ from other strawbale construction techniques in that the bales themselves support the weight of a roof. They require no additional beams or corner-posts because strawbales themselves are fully capable of supporting the weight of a light roof.
Because of the ease of constructing a load-bearing strawbale building, a small strawbale home can be constructed by a group of five people in as little as a week (I’ve seen it done!). The downside of load-bearing strawbale houses is that they may not fit local building requirements and are more difficult to maintain.
Strawbale Construction Method: Insulation Only
Strawbales can be used solely as an insulative material in a structure that already has sturdy walls and roof support. I have worked to make metal buildings, like grainbins and back-yard sheds, livable by insulating them with strawbales or clay-straw slurries. This is probably the most ideal form of strawbale construction because it requires very little work but rewards builders with sustainable insulation.
Fortunately for those interested in green remodeling, strawbale is extremely inexpensive compared to synthetic insulation. Strawbales can be stacked inside a premade structure to increase its thermal mass, making it cooler in the summer and warmer in the winter. A layer of stucco, clay, or lime plaster on the inner walls makes the inside of the building both flame-resistant and attractive.
Lining any strawbale structure with some form of plaster is usually the final step in completing the construction project. This is often an opportunity to experiment with artistry; intricate designs can be sculpted into the plastered walls of a strawbale building. Following the completion of this final step, a strawbale building is energy-efficient, fire-retardant, and earth-friendly in every way.
Sources: Personal Experience; Strawbale.com Accessed 23 Dec 08.
