Post & Beam Straw

Part One - Foundations & straw bale walls

Probably the most common form of construction using straw bales. The structure can be wood (traditional post & beam, or modified), steel or masonry. The straw bales are infill; they provide the insulation and the surface of the wall. They support only their own weight and not the floor or roof.

Back to Building with Straw

After pouring the footer, the work on the foundation can begin. Durisol ICF (insulated concrete form) blocks were used. The foundation wall is two layers thick with added mineral fiber insulation. The wider wall rises 12" above grade and takes the full depth of the bales. A metal separation is provided between the bales and the foundation. Concrete fills the interior of the forms. The first course of the bale wall is secured to the foundation by rebar set into foundation.

The structural steel frame is assembled on-site. Steel was selected for a variety of reasons. The frame is certified recycled content and produced regionally - supporting the local economy and reducing shipping. The steel is pre-cut to size with no construction debris.

The steel frame provides for a much larger roof span as well as longer spaces between the posts. With less posts, there is less fitting of bales around the structure.

With the post & beam structure finished the bale stacking begins. The construction schedule was dependant on when bales become available as it is best to use fresh cut materials. The first course should be set carefully and as accurately as possible. As the bale raising continues the courses should be staked at least every two courses with bamboo dowels. The straw bales should be stacked with staggered joints. A level should be used to keep the bale wall both horizontally and vertically. If the wall is not plumb it can pushed back into line.

Custom bales can be fitted around structural elements. In this case the line of structure is on the inside of the wall - so the exterior is a continuous line of bales; this provides optimal insulation value. Door and window openings are set to the outside of the wall to create deep window seats or sills. It also offers better protection from water infiltration at these connections.

After stacking the walls can be shaped to create smooth curves at windows, doors and corners. Niches and details can be added to the interior. A variety of tools can be used to sculpt these unique elements. The finish of the wall can be very smooth and level, undulating or bumpy - depending on the desired look. For a smooth wall, the bales will be trimmed prior to plastering. Undulating walls occur naturally. Curvy walls can be stacked irregularly, or shaped after. The creative nature of working with bales is one of the most satisfying and beautiful.

Rough electrical can be added as the walls are being stacked, or once it is finished. The boxes are attached to a 2 x 4 stake. This is then pounded in the desired location. The wires run between course of bales or cut into the bale. Wires can be run through the wall by using a bale needle.

Mechanical vents and other wall penetrations are easily cut as needed through the wall. The only systems that can not run in or through the bale walls are water or waste lines.

Continue

PartTwo - Envelope enclosure & plastering

PartThree - Finish materials & interior details.