Exterior foundation waterproofing
Keeping water off the outside of the wall is the most complete fix and the most disruptive one. Here's what to expect.
Every other basement repair handles water after it has reached the foundation. Exterior waterproofing is the one that stops it outside. The crew excavates a trench along the wall all the way down to the footing, scrapes and cleans the masonry, and applies a waterproofing membrane, usually covered by a dimpled drainage board that lets water fall freely to the bottom. There, a new perforated footing drain in stone carries it to daylight downhill or to a sump. Backfill goes in, and the final grade is shaped so rain runs away from the house.
Who usually chooses the outside route?
- Owners finishing a basement who want the walls themselves dry
- Houses whose original clay or plastic footing drain has collapsed or silted shut
- Homes cut into a slope where one wall takes almost all the water
- Fieldstone or brick foundations losing mortar to water pushing straight through
- Any job where the wall has to be uncovered anyway for structural work
Why can't every wall be dug?
Obstacles. Front porches, attached garages, driveways, patios, mature maples and gas meters all sit right where the trench needs to go. On many Elmira streets the next house is close enough that one side of yours has no room for an excavator at all. Sloped lots in Southport and on the hills above the valley can mean a much deeper cut on the uphill wall. That's why plenty of jobs end up as a mix: the uphill or worst wall done from outside, the rest handled with interior drain tile.
What's required before digging starts?
Under New York's one-call rules, the excavator has to contact Dig Safely New York through 811 at least two and no more than 10 full working days ahead, so gas, electric, water and telecom lines get marked. The contractor should make that call and wait for the paint and flags. NYSEG also recommends that homeowners who dig on their own call first. Ask too whether your city, town or village wants a permit for the job.
Questions worth asking
- What membrane or coating are you using, and what protects it while you backfill?
- Where will the footing drain discharge?
- Who restores the lawn, plantings, walks and steps, and how?
- What's the plan if the wall is cracked or bowed once it's exposed?
What affects the price?
- How deep the footing is and how many feet of wall are dug
- Machine access, or hand digging near utilities and tight spots
- Removing and replacing concrete, pavers, steps or a porch
- Repairs that turn up once the wall is uncovered
Prices come from the waterproofing company once someone has stood in your basement, checked the walls, the floor joint and the sump, and looked at where roof and yard water goes outside. We don't quote prices, and an honest number can't be given over the phone before anyone has seen the water's path.
Where we connect you with help
Common questions
Is exterior waterproofing better than interior drain tile?
Neither is better everywhere. Exterior work keeps the wall itself dry but means excavation and yard repair; interior drain tile is less disruptive but manages water after it arrives. The lot, the foundation and your plans for the basement decide it.
Can just one wall be done from outside?
Yes, and it's common. Often only the uphill or worst wall gets excavated, while the others are treated from inside or don't need anything.
Related services
More background: Chemung County basement water guide.
Water at the base of the wall, a crack that drips, or a sump you don't trust?
Call and a Chemung County waterproofing company will come trace where the water is getting in.