What would be the best way to seal the gaps between the bricks of my foundation?

The best way to seal gaps between the bricks of a foundation wall is to repoint the mortar joints, dig out the loose crumbling mortar and pack in fresh mortar, then control the water that made the joints fail in the first place. Caulk and spray foam are not the fix. They cover the gap, they do not rebuild the joint. On a 603 job we repoint the wall and then deal with the groundwater driving the decay, because new mortar in a wet wall just crumbles again.

Here is the plain version. In a brick or stone foundation, the brick is rarely the problem. The mortar between the brick is. It breaks down after years of New England moisture and frost, turns to powder, and leaves the gaps you are looking at. Seal the gap without fixing why the mortar failed and you are back here in a couple of seasons.

Why the mortar lets go

Water shows up at your foundation because the soil packed against it is disturbed backfill. That is the looser dirt put back when the house was built. It drains slow and holds water, so after a hard rain or a spring thaw the wall stays wet. Then NH frost heave pushes on those walls all winter. Wet brick plus that freeze and thaw works the mortar loose, joint by joint, year after year. That is the engine behind the gaps.

So a tube of caulk is the wrong tool. It hides the symptom. The wall keeps getting wet, the next joint goes, and now you are chasing gaps forever.

The fix that actually holds

Repointing is the real answer for the gaps themselves. We rake out the dead mortar to a sound depth and pack in fresh mortar so the joint carries load again and water stays out. On older brick and fieldstone walls we match the mortar to the wall so the new work does not crack the brick around it. That is the seal that lasts.

Then we handle the water. If the wall is wet because groundwater is sitting against it, we fix the drainage too. In a basement that is interior drainage, our Forever Dry System, full-perimeter drain to a sump and out. A dry wall keeps mortar in one piece. A wet wall eats it.

We do not seal a brick wall from the outside by digging it up and coating it. Nik has watched those exterior fixes fail in about two to three years once the ground settles and the coating cracks. That is our field experience, not a promise about every job. We seal and drain from the inside, where the work stays put.

When the gap is more than a gap

Sometimes loose joints are the wall telling you it is moving. If the brick is bowing inward, if whole sections are shifting, or if stones are dropping out, that is not a repointing job anymore. That is structural and foundation repair. We stabilize a bowing wall with carbon-fiber straps or a power brace, and we lift or hold a settling wall with helical piers. You repoint after the wall is stable, not before, or the new mortar cracks right back open.

You may not need all of that. A few crumbly joints on a wall that is straight and dry is a small repoint. We will tell you that when we look. No sense selling you straps and piers for a wall that just needs its joints packed.

What it costs

Repointing brick or stone joints is priced after we see the wall, because it depends on how many feet of joint are bad, how deep the mortar has gone, and whether the wall is moving. We price that after we see it, and the on-site look is free. If the gaps come with a structural problem, those repairs do have set numbers. Carbon-fiber straps run $850 each, a power brace runs $1,300 per brace, and helical piers run $2,700 per pier for the first three, then $2,200 per pier after that. A poured-wall crack, which is a different animal from a mortar joint, runs $1,000 to $3,000 to inject. You get every figure in writing within 24 hours, so you are not guessing.

A dry, sealed foundation is also worth real money to your house. The Insurance Information Institute notes that water damage is one of the most common home insurance claims, and a leaky foundation wall is a fast way to get there. Sealing the wall right is cheaper than the rot, mold, and repairs water brings once it is inside.

What this means for your home

If you can brush mortar out of the joints with your hand, or daylight shows through a gap, do not reach for caulk. Repoint the joints with fresh mortar and fix the water keeping the wall wet. If the wall is also bowing or stones are shifting, stabilize it first, then seal. We have done this work for 5,000+ homeowners across New England, and we self-perform it with our own crew. Angel runs our waterproofing side, so the seal and the water get handled together. Repointing carries our workmanship standard, and the drainage and structural work carry their own warranties, like 25 years on wall stabilization and a full transferable lifetime warranty on the Forever Dry System.

Ready to look at it?

We will come out, find out why your mortar is failing, and tell you whether it is a simple repoint, a repoint plus drainage, or a structural fix first. The on-site inspection and written estimate are free, and we get you a quote within 24 hours.

Call us at 603-610-1770, or book your free inspection. We back every job with the 603 guarantee.

Related questions

Can I just use caulk or spray foam to seal foundation gaps?

No. Caulk and spray foam cover the gap but they do not rebuild the mortar joint, and they do not stop the water working the joints loose. The wall stays wet, the next joint fails, and you are sealing gaps forever. Repointing packs the joint back with real mortar, and pairing it with drainage keeps the wall dry so the new mortar lasts. That is the fix that holds.

Should I seal my brick foundation from the inside or the outside?

We seal from the inside. Outside sealing means digging up the foundation and coating the wall, and in our field experience those coatings tend to crack and fail in about two to three years once the ground settles. We repoint the joints from inside and, where groundwater is the cause, add interior drainage with the Forever Dry System. Inside work stays put and you are not paying to excavate your yard.

Do failing mortar gaps mean my foundation is unsafe?

Not always. A few crumbly joints on a wall that is straight and dry is a maintenance repoint, nothing scary. It becomes a safety issue when the wall starts bowing inward, sections shift, or stones drop out, because then the wall is losing its grip on the house above. That is structural repair first, with carbon-fiber straps at $850 each or piers, then you repoint. We will tell you which one it is when we look.

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?