The Best Way to Fix a Leaky Foundation

Review the Leak

• Before attempting to fix a leak, review the location, impact and cause. You will be making repairs to the exterior wall of the foundation, so you need to locate the troublesome wall from the inside first. The leak could be caused by ground water or surface water. If a nearby stream or creek is leaking into the basement, divert the water from the house using rocks or other obstacles. If the leak is caused by groundwater, you will have no choice but to waterproof the problematic outer foundation wall. Finally, review the severity of the leak. If it isn't causing damage to your foundation's walls, it may not be worth doing a difficult and time-consuming repair.

Dig down

• Once you have determined that you have no choice but to fix the leak, begin by digging deep into the ground beside the leaky exterior wall. Make a wide trench that goes all the way to the bottom of the wall and is wide enough to fit a person. You will have to climb into the ditch and move around to make repairs to the exterior wall.

Cover and Drain

• If the wall is made of cinder or cement blocks, you will begin by covering it with a layer of pasty premixed cement plaster. Spread the layer evenly across the wall, using a flat trowel. Cover the entire thing with a thick coat of plaster. It will take a few days for the plaster to dry, so try to choose a sunny week to do the repairs, or your ditch could collect water and flood the foundation more.
  If you have a foundation made of solid poured cement, you will not have to put on a layer of plaster. Begin, instead with this second step:
  Once the plaster dries, add a thick layer of foundation tar. Allow this layer to dry for a few days.
  Finally, add a drainage pipe to the bottom of the pit along the exterior wall. This should help move water away from the foundation. Bury the pipe and replace the earth around the house.