should I use stone under my cellar floor

by Donna
(Tiverton, RI)

Q. I am planning to concrete my cellar and I get water sometimes. My cellar is dirt. Should I lay stone before I lay the concrete.

A. Yes. First determine how much head room you need. You may need to dig out some of the existing sub-base before adding crushed rock. Check the building codes in your area.

Once the sub-base is ready and level add two to three inches of 3/4 inch crushed rock over it. Level the rock by using a laser level or measuring down from your existing floor joists.

Next, install a layer of 6 mil poly over the crushed rock. Be careful not to poke any holes in it. This will help keep moisture vapor from coming up through the new concrete floor.

If you have any water coming in through your foundation walls the next step would be to cut some strips of 2 inch styrofoam about 4 inches wide by 8 feet long. Lay these strips around the inside perimeter of the foundation walls on top of the crushed rock.

After you're done you should have a 4 inch high band of styrofoam (with no gaps, lying on top of the rock) lining the inside of your cellar. Place a sump pump bucket in one corner and right up against the styrofoam. Poke holes in the bucket at the height of the crushed rock. This will collect water that runs through the rock.

Your new concrete floor will be poured inside the styrofoam. The foam will be removed the next day and leave a 2 inch wide gap to collect any water that leaks from the foundation walls. Install rock in the 2 inch gap and at the same level as the new concrete floor.

Cut a groove in the sump bucket where it contacted the styrofoam so the water from the 2 inch gap can run into the bucket.

This system will keep your cellar floor completely dry. The rock will collect any water coming up from the sub-base and it will find it's way to the sump bucket. The 2 inch "french drain" will collect any water from the foundation walls and also direct it to the sump bucket.

If you already have a drainage system in your basement, you can do without the sump pump bucket and direct the "french drain" to one corner of the cellar and into the existing drainage.

For more information go to BASEMENT FLOOR WATERPROOFING.