How to build a concrete foundation

Building a new concrete foundation means excavating, setting footings below the frost line, forming and pouring the walls, then waterproofing and backfilling before the house goes up. We do not build new foundations. We are the crew you call when an existing one cracks, leaks, settles, or starts to bow. So this page walks you through how a new pour goes, then where we fit once that concrete is in the ground.

A new foundation starts with the dig. The footing is the wide base that carries the wall, and it has to sit below the frost line. In New Hampshire that line runs deep. Frost heave pushes hard up here, and footings set too shallow will move. Forms go up, rebar goes in, then the concrete gets poured for the footings, then the walls. After the concrete cures, the walls get a waterproof coating, drainage goes in at the footing, and the dirt gets put back.

That last step is the one that comes back to bite people years later. The soil packed against a fresh foundation is disturbed backfill. It is the loose fill they put back when the house was built. It drains slowly and holds water. So water pools right against the wall, season after season. That is why a foundation that was fine on day one starts leaking at the floor wall joint a decade later. Nothing was done wrong. It is the backfill doing what backfill does.

That is also where we come in.

When your existing foundation cracks, settles, or leaks, we fix it. We do not dig the outside out and re-coat it. In our field experience that exterior fix tends to fail in two to three years. The durable repair is interior. For wall cracks, we use crack injection, epoxy or polyurethane, and that runs $1,000 to $3,000. If a wall is bowing inward from frost and soil pressure, carbon-fiber straps lock it in place at $850 each, or a power brace at $1,300 per brace for heavier movement. Both carry a 25-year warranty on the wall stabilization.

If the footing has settled and the foundation is sinking, that is a piers job. Helical piers drive down to stable soil and carry the load, and they run $2,700 per pier for the first three, then $2,200 per pier after that with a 25-year engineered warranty. We install those ourselves, in-house. Sagging floors or a tired carrying beam get lally columns and floor support at $1,300 to $2,500. A rotted sill or beam gets sill and beam replacement at $7,000 to $40,000. If a wall needs a second wall built inside it for support, that is an auxiliary wall at about $1,350 per linear foot.

A full foundation-wall rebuild or steel I-beams are a different animal. We do not put a price on those over the phone. We price that after we see it.

If you are planning a new build, you do not need us yet. Call a foundation contractor who pours new concrete. Come back to us once it is built and something goes wrong, or if you bought a house and the existing foundation needs work. And if your basement is just damp, not cracked, that is a waterproofing job, not a foundation job. Our Forever Dry System handles a wet basement. The foundation work above is for concrete that has moved or failed.

Footings below the frost line is not just a New Hampshire habit. It is in the building code, and your local building inspector will check it. The Insurance Information Institute (iii.org) also notes that most homeowners policies do not cover foundation settling from soil movement, so getting it right the first time matters.

For more on the structural side, see our structural and foundation repair hub, foundation repair, helical piers, sill replacement, and supplemental support. Every repair we do is backed by the 603 guarantee.

Cracked, settling, or leaking foundation? Call us at 603-610-1770 or book your free inspection. Free inspection, free estimate, and a written quote within 24 hours!

Related questions

Do you build new foundations from scratch? No. We repair existing foundations. We do crack injection, carbon-fiber straps, piers, lally columns, sill replacement, and more. For a brand-new pour, call a contractor who does new construction, then call us if it ever needs repair.

How deep does a foundation footing go in New Hampshire? Below the frost line, which is deep up here. The exact depth is set by code and checked by your local building inspector. Footings set too shallow will move with frost heave.

Why does my foundation leak years after it was built? The disturbed backfill against the wall drains slowly and holds water. Water pools at the foundation and finds the floor wall joint. A new pour can be flawless and still leak later for this reason.

Can you fix a bowing foundation wall? Yes. Carbon-fiber straps at $850 each hold a wall that is bowing from frost and soil pressure, and a power brace at $1,300 per brace handles heavier movement. Both carry a 25-year warranty.