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.
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
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.