Is it a good practice to put a coat of waterproofing on my foundation?

A coat of waterproofing on the foundation wall is a short-term patch. In our field experience it usually fails in about two to three years, because the water is not coming through the wall. It is coming up from the ground around and under the foundation. The fix that holds is interior perimeter drainage.

Here is what is going on. When your house was built, the crew dug a hole, set the foundation, then backfilled. That disturbed backfill is looser than untouched ground, so it drains slow and holds water. Rain and snowmelt pool against your wall, and NH frost heave pushes the walls inward all winter, so the pressure comes from outside and below all the time. A coat of paint or tar on the face of the wall does nothing about it. Water finds the weak spot, a hairline crack, the floor wall joint where the wall meets the slab, a tie hole, gets behind the coating, and the coating peels. You are back where you started.

People think exterior excavation waterproofing is the gold standard: dig the wall out, coat it, backfill. We do not do that work. Nik has watched too many of those come back in two to three years. You disturb the soil again, the coating is only as good as the day it goes on, and you have spent money and torn up the yard for a fix that does not last.

What lasts is moving the water instead of blocking it, which we do from the inside with the Forever Dry System: cut a channel around the inside perimeter, lay drainage that carries water to a sump pump, line the walls with a 12-mil vapor barrier, and add a dehumidifier to dry the air. The sump runs a half horsepower for every 120 feet of drain. The basement stays dry, 100% guaranteed to be dry for life!

The Forever Dry System is for basements only. A crawl space needs crawl space encapsulation, with a 12-mil wall and 20-mil floor vapor barrier, drainage matting, sealed seams, and a dehumidifier. Do not let anyone put a basement system in a crawl, or sell you paint and call it waterproofing.

When the wall itself is the problem

Sometimes a coating question is really a structural one. For a leaking crack, the fix is crack injection, epoxy or polyurethane pushed the full depth so it seals front to back, not a coat on top. It runs $1,000 to $3,000 and carries a 10-year warranty.

If the wall is bowing from frost and soil pressure, paint does nothing either. That is where carbon-fiber straps stabilize the wall, at $850 each with a 25-year warranty, or a power brace at $1,300 per brace. If the foundation is settling, that is piers. Helical piers run $2,700 per pier for the first three, then $2,200 per pier after that with a 25-year engineered warranty.

Most of the time, though, the wall is fine and the problem is water management. You do not need structural work just because your basement is damp, and we will tell you if all you need is drainage and a sump. No upsell.

A coat is cheap up front, but when it fails you pay again to handle the water it let through and still need the real fix. Interior drainage costs more on day one, then it is done. Basement waterproofing with the Forever Dry System runs $3,000 to $30,000, depending on perimeter and any wall work. The Department of Energy treats foundation water as a drainage and air-control problem, not a coating problem (Source: DOE Building America).

So, should you coat it?

If you are selling next month and want the wall to look clean, a coat might do that. For a basement that stays dry, no. Put the money toward interior drainage and a sump, the fix that holds in NH, ME, and MA ground and the one we stand behind for life, for more than 5,000 homeowners across New England.

Call us at 603-610-1770, or book your free inspection. Both the inspection and the written estimate are free, and Angel, who runs our waterproofing side, has seen every kind of wet wall there is. See the 603 guarantee for what dry-for-life actually means.

Related questions

Does waterproofing paint stop a leaking basement wall?

Not for long. Waterproofing paint sits on the face of the wall and does nothing about the water pressure pushing from the soil outside. Water finds a crack, the floor wall joint, or a tie hole, gets behind the paint, and the paint peels. In our field experience these coatings fail in about two to three years. The fix that lasts is interior perimeter drainage that carries the water to a sump pump, which is the Forever Dry System, guaranteed dry for life.

Is exterior foundation waterproofing better than interior drainage?

We do not think so, and we do not do exterior excavation waterproofing. Digging the whole wall out and re-coating it tears up your yard, disturbs the soil again, and the coating is only as good as the day it goes on. Nik has seen too many of those come back in two to three years. Interior drainage moves the water to a sump instead of trying to block it, and that is the fix that holds up in New England ground.

How much does it cost to actually fix a wet basement in New Hampshire?

Basement waterproofing with the Forever Dry System runs $3,000 to $30,000, depending on how much perimeter drainage you need and whether the walls need any work too. If the wall has a leaking crack, crack injection runs $1,000 to $3,000. If a wall is bowing, carbon-fiber straps run $850 each and a power brace runs $1,300 per brace. We come out, look, and give you a written quote within 24 hours. The inspection is free.

Related answers: More foundation answers · If someone sealed a basement crack completely with liquid sealant, is the foundation problem fixed? · What are the pros and cons of a stone foundation? · What is the difference between helical piles and push piers?