May 2009 - Concrete Walls and Slab

Here i am moving the gravel by tractor into place where it is spread and leveled at the subgrade elevation. That is the level of the bottom of the concrete slab.

Trucks of Pea Gravel and crushed rock drove onto the pad and dumped as close as possible so that we didn't have to move it all too far to get it level and in place.

After the footings were poured, the next step was to pour the concrete foundation walls. THe footings and the bottom of the footing were located below the frost line. This is a major structural requirement in climates where the ground freezes, as the frozen ground will move UP ,or heave up. If the bulding foundation is not built below the frost line, the whole bulding will have a signficant chance of heaving up in the winter. The top of the walls are at an elevation of 6" above where we anticipate the final grade around the building will be.

Because time was tight, we placed pea gravel fill over the existing ground elevation to bring the overall ground elevation to the underslab elevation. The concrete slab floor will be poured on this. We used our Kobota tractor to bring in nearly 80 cubic yards of fill. Mostly we used pea gravel, because it doesn't need to be compacted and it spreads very easily to the bottom of slab elevation. Areas where the concrete slab has to pull into will be filled with 5/8" crushed rock which will hold the truck very well. Both fills work well for the concrete, but 5/8" will be rock hard for supporting the concrete truck. If pea gravel was used there, the concrete trucks would spin its tires and ruin the subgrade preparation. One of those "experience" things!

Here is the ground after the concrete walls were poured and prior to the gravel being put in.

Here we are putting in gravel!

Now we are ready to proceed with the concrete slab and all the things that go in and under it!