How to waterproof a basement wall on the outside of the foundation

You waterproof the outside of a foundation by digging down to the footing, cleaning the wall, coating it with a membrane, and adding drainage and gravel backfill before you bury it again. That is the textbook exterior method, and it works on paper. In our field experience it does not hold up. The fix tends to fail in about two to three years once the membrane cracks or the soil settles, and you are back to digging. We do not do exterior excavation waterproofing for that reason. The durable fix is interior drainage, and that is what we install.

Here is why the outside route disappoints so often.

When your house was built, the crew dug a hole, poured the foundation, then pushed the dirt back in around it. That refilled soil is called disturbed backfill. It is looser than the packed ground next to it. So it drains slowly and holds water right against your wall. Add a New Hampshire winter and frost heave starts pushing the wall inward. An exterior coating sits in that wet, moving soil. Once it cracks, water finds the path again.

Digging it back up is the worst part. To re-coat an exterior wall you excavate the full depth of the foundation, sometimes eight feet down, around the part of the house that is leaking. That means moving decks, walkways, gardens, and sometimes a driveway. Then you do it all again when it fails.

What we install instead

We stop the water on the inside, where we can reach it for life. Our basement fix is the Forever Dry System. We cut a channel along the inside floor wall joint, lay full perimeter interior drainage, and run it to a sump pump. The pump is sized at half a horsepower for every 120 feet of drain. We add a 12-mil wall vapor barrier and a dehumidifier so the room stays dry and the air stops smelling like a cellar.

That system is 100% guaranteed to be dry for life! The warranty is a full transferable lifetime warranty (transfer is conditional, and it voids if another contractor or homeowner touches the work). Basement waterproofing with the Forever Dry System runs $3,000 to $30,000.

The Forever Dry System is for basements. If your problem is a dirt or low crawl space, that is a different job called crawl space encapsulation. There we line the walls with a 12-mil vapor barrier, the floor with a 20-mil barrier over dimpled drainage matting, seal the seams, and add a dehumidifier and sump. Crawl space encapsulation runs $3,000 to $25,000. The Department of Energy notes that up to about a third of a home’s heat loss can come from an uninsulated foundation or crawl space, so sealing it pays you back in comfort too.

When the wall itself is the problem

Sometimes water is the symptom and the wall is the real issue. If you see a horizontal crack, bowing, or a wall leaning in from frost pressure, drainage alone will not fix it. That is structural work. We use carbon-fiber straps to stabilize a bowing wall, a power brace where the wall needs to be pushed back over time, or helical and push piers when the footing is settling. A single leaking crack with no movement is usually just a crack injection, epoxy or polyurethane, and you do not need the bigger repair yet.

If you are reading this hoping to skip a contractor, here is the plain part. You do not need exterior excavation. It is the most expensive way to chase a wet basement, and it is the one most likely to come back. Start with what is causing the water, then match the fix.

Want to see which fix your wall actually needs? We will come out, look, and tell you what we find. Free inspection, free estimate, and a quote within 24 hours. Financing is available through Hearth, subject to approval, and we make nothing on it either way.

Call us at 603-610-1770 or book your free inspection. We serve New Hampshire, Maine, and Massachusetts out of East Kingston, NH. We are trusted by more than 5,000 homeowners in New England, rated 4.9 on Google across 250 reviews, and BBB A+ accredited.

Learn more on our basement waterproofing page, our crawl space services, our structural and foundation repair and foundation repair pages, helical piers, and the 603 guarantee.

Related questions

Does exterior foundation waterproofing last? In our experience it tends to fail in about two to three years once the membrane cracks and the disturbed backfill keeps holding water against the wall. Interior perimeter drainage with a sump is the fix we stand behind for life.

Can I waterproof my basement from the inside instead of digging outside? Yes, and we recommend it. Our Forever Dry System routes water along the inside floor wall joint to a sump pump, adds a 12-mil wall vapor barrier and a dehumidifier, and is guaranteed dry for life. It runs $3,000 to $30,000.

Why does water pool against my foundation in the first place? The soil right next to your foundation is disturbed backfill, the looser dirt put back when the house was built. It drains slowly and holds water against the wall, and New Hampshire frost heave then pushes that wall inward.

What if my basement wall is cracked or bowing, not just wet? That is structural, not just a drainage job. We use carbon-fiber straps for a bowing wall and helical or push piers for a settling footing. A single non-moving crack is usually a crack injection, $1,000 to $3,000, and nothing more.