To help reduce the cost of our home, we are planning to utilize a rubble trench foundation or dry wall footing.
Rubble trenchs are a construction approach popularized by architect Frank Lloyd Wright.
The general plan is to use loose stone or rubble, in a trench, thereby minimizing
the not only our cost (less cement) but also the amount of embodied energy used.
Due to the lower embodied energy, lower material cost and comparable results,
we've selected the rubble trench approach.
The goal of the foundation is to bear the imposed structural while also
providing adequate drainage of ground water to prevent expansion or weakening of soils and frost heaving.
To construct the foundation a narrow trench will be dug (we will determine how deep
later). The bottom of the trench will be gently sloped to provide drainage to a
pipe routed to "daylight" (graded 1":8'). We plan to first place a fabric
filter, clean pea gravel 4" thick, and then a drainage piple. The trench will
then be filled with stone.
A steel-reinforced concrete grade beam will then be poured at the surface
for our stem wall. We plan to insulate the grade beam to lateral heat loss via XPS foam board, which
we currently plan to place inside the stem wall.