First, make sure that rainwater runs away from the house foundation. To pinpoint problem areas, go outside while it's raining and observe how the water flows off the roof and onto the ground around the house. Pay particular attention to areas below roof valleys where lots of water runs off.
Add soil to slope the ground away from the foundation. The grade should slope a minimum of 1 in. per foot for the first 4 to 6 ft. If necessary, direct roof water away with gutters and downspouts.
If these measures fail, you may have to install an interior drain tile and sump basin. The corrugated floor edging catches water running down the inside of the foundation wall and seeping under it and then directs it to the drain tile. The drain tile carries the water to the sump basin, where an electric pump automatically discharges it.
The materials are relatively inexpensive, but the labor is huge. You'll need to jackhammer out a strip of concrete around the perimeter, haul out concrete rubble and dirt, carry in gravel, and then patch the concrete floor. This is dusty, sweaty labor. Pros charge several thousand dollars for this job.
To install this system, follow these steps:
- Break out and remove an 18-in. strip of concrete around the walls to expose the footing and underlying dirt. Rent an electric jackhammer for this task.
- Dig a 12-in. wide by 8-in. deep trench alongside the footing.
- Find a location for the sump basin (an unfinished room is best). You'll need an electrical outlet for the sump pump and a way to run the discharge pipe outside. Break out additional floor, dig a hole and set the basin in place so the top is flush with the concrete floor.
- Lay about 2 in. of gravel in the bottom of the trench (use crushed stone or river rock). Run the perforated drain tile in the trench and push its end through the knockout of the sump basin. Try to make a complete loop of the basement with the drain tile and run both ends into the basin. Fill the trench and around the basin with more gravel, leaving room for 3 to 4 in. of concrete.
- Hang 6-mil polyethylene sheeting from the top of the foundation wall. Leave the bottom edge hanging just above the footing.
- Lay the floor edging on the footing. Make sure the polyethylene runs behind it.
- Lay a strip of polyethylene on top of the gravel and pour concrete to patch in the floor.
- Install the sump pump in the basin and run the discharge pipe outside. Make sure the pipe runs at least 6 ft. away from the foundation so you aren't just dumping the water back against the foundation wall.
If you have a concrete block foundation, you'll have to drain the block cores by drilling 1-in. holes through the face of the block. Rent a rotary hammer with a 1-in. masonry bit; it's worth the cost.