We wanted to get the first floor deck on before we poured the slab in the basement to help protect the concrete from the sun. Now that the deck is complete we move to the basement.
We had several tasks. 1. Wrap the center concrete pier in 6″ of rigid foam (a total of R30). The pier was poured on 6″ of foam when we poured the walls. 2. Install a radon perimeter pipe and a floor drain pipe. 3. Spread 4″ of clean gravel to level the floor. (Yes, that’s a tractor in our basement!) 4. Tamp down the gravel (I love a good tamping). 5. Attach drainage plane to the interior of the basement wall. This allows any condensation or water to drain down the concrete walls and out over the footing. We’re using a material that is generally used on the exterior, but it will work well for us as a drainage plane and air seal to keep any radon gas out. 6. Install 4″ of rigid foam on the floor over the gravel, lay down our poly vapor barrier and tape and seal to drainage plane.
We still have to attach 2″ of foam to the walls and then (finally) install the last 2″ of foam on the floor. (Later we will add 9″ of cellulose to the walls.) Then we will be ready to pour 4″ of concrete for the floor slab.
The basement is the weak link in most homes. Its considered a conditioned space since there is usually no insulation between the first floor and the basement, but it is cool and damp in the summer and bleeds heat from the house in the winter. We will have an R30 floor and R40 walls to match the rest of the house. Our efforts should even out the temperature swings and lower the potential for moisture and mold problems even though we’re not directly heating or cooling the space.