What is done
The soil against the wall is dug out down to the footing. The wall is cleaned and any cracks are patched. A waterproof membrane is applied, often with a drainage board over it, and a perforated pipe in gravel is laid at the base to carry water to daylight or to a sump. Then the trench is refilled, usually with stone near the wall so water drains down instead of sitting against it.
When it makes sense
- One wall is the problem, such as the uphill wall of a walk-out basement.
- The basement is finished and you would rather disturb the yard than the rooms.
- The wall is already being exposed for another reason, such as a new addition.
- A block wall is taking in so much water that draining it from inside would leave it permanently wet.
It makes less sense where a deck, a driveway, an air conditioner pad or a neighbor's fence sits tight against the wall. Each obstacle has to be removed and rebuilt, or worked around by hand.
Before anyone digs
Tennessee law requires a locate request before excavation. Tennessee 811 takes requests at 811 or (800) 351-1111, and asks for at least three working days' notice. Utility owners then mark their buried lines with paint or flags. A ticket stays valid for fifteen calendar days from the start date given.
The marks cover lines the utilities own. They do not cover what belongs to you: a wire to a shed, sprinkler pipes, a septic line. Tell the company about anything you know is buried.
Deep trenches beside a house are dangerous. Stay out of them, and keep children and pets away until the soil is back.
What to ask
- How deep is the footing, and how will the trench walls be kept from caving in?
- Where does the new footing drain empty?
- What membrane is used, and is it a coating, a sheet or both?
- What is the plan for plants, paving, steps and the air conditioner along that wall?
- How will the refilled soil be compacted, and who returns if it settles?
Exterior questions
Is tar on the wall the same as waterproofing?
No. The black coating builders brush on is damp-proofing. It slows moisture vapor and is not made to resist water under pressure or to stretch over a crack.
Can exterior work be done on a crawl space?
Sometimes, on a low wall where water runs straight in. More often the cheaper answer for a crawl space is better drainage at the surface and a drain inside.