Build Phase 3 – Rubble Trench
Concrete foundations are expensive and would require a lot of concrete, even for our small building. We needed a foundation that could handle the large volumes of water that we get in our yard.
Through a ton of research over a number of weeks, I came across the rubble trench foundation. Basically you dig the size trench you want for the foundation and fill it with a layer of gravel, then bricks, or broken concrete or rubble. We had a lot of broken concrete from the shed foundation we tore down, so we used that. There are plenty of people looking to get rid of rubble, concrete and bricks. Often they will gladly give it away free, if you pick it up.
After the desired depth has been reached, a minimum of 6” of concrete is poured on top of the rubble trench. Rubble trenches have a long history, but cannot be used for basement spaces and are not often used in cold climates. Rigid foam was used to for the rubble trench foundation form work.
We filled the trench with rubble, bricks and broken concrete. The trench is graded towards the drainage system. Concrete foundations require specifications to insure good soil drainage, the rubble trench foundation serves both foundation functions at once.
Concrete dries surprisingly fast. We had to be quick! We placed rebar to help support the concrete from cracking, as well as providing more strength to the integrity of the foundation. Lastly we cut away any excess foam forms.