What this covers
Basement waterproofing keeps water out of a below-grade space, from the inside, the outside, or both. Interior systems cut a channel along the base of the wall, set a perforated drain in gravel that leads to a sump, and run a dimpled membrane up the wall so any seepage drops into the drain. Exterior systems excavate to the footing, apply a membrane to the wall, add a footing drain and backfill with gravel. The company first finds where the water enters: wall cracks, the cove joint where wall meets floor, window wells or the floor itself, and chooses the method to match. Fixing gutters and grading outside is part of the job.
When to call
- Water at the joint where the basement wall meets the floor after heavy rain.
- Damp stains, white mineral deposits or peeling paint on the lower part of the walls.
- A musty basement, rusted appliance feet or mold behind stored boxes.
- A basement you plan to finish, or one being rebuilt after a flood.
What to expect
- Find the sourceThe company inspects walls, floor, window wells and the outside grade, during rain if possible.
- Choose the systemAn interior drain, exterior membrane or a combination is proposed, with the sump and discharge route.
- InstallThe channel is cut, drained and patched with the membrane set, or the exterior is excavated and sealed.
- Test and finishThe sump is run, the discharge checked, and the area cleaned for finishing.
Get a certified company
Look up a certified company by ZIP code. Every company's license, insurance and trades are verified before it is listed, and placement is never paid.
Questions people ask
Interior or exterior waterproofing?
Exterior stops water before it reaches the wall but needs excavation and access around the house. Interior systems manage water that gets in and are less disruptive. Many homes get an interior drain and sump plus grading and gutter fixes outside.
Does the interior channel show?
A narrow strip of new concrete along the wall and a membrane on the lower wall, both covered when the basement is finished. The sump basin has a sealed lid.
Is waterproofing paint enough?
Coatings can slow dampness through a wall but do not stop water under pressure or at the cove joint. They are a finish, not a drainage system.
Related: Sump pump installation · French drain installation · Basement finishing · All foundation, basement and drainage
This page describes what the service involves. The company you hire sets the scope, the schedule and the price, and your contract is with that company. We verify credentials and collect reviews from real jobs. We do not guarantee any company's workmanship. Safety steps are general guidance. When in doubt, leave the home and call 911.