Is it better to put down a concrete slab or use concrete blocks for a foundation repair?

For most New Hampshire repair jobs, neither one is your real choice. A poured concrete slab and a block wall are two different parts of a foundation, and which is “better” depends on what is actually failing. We do repair, not new builds, so what matters is fixing the wall, footing, or floor support you already have, priced after we see it. Crack work runs $1,000 to $3,000 and floor support starts at $1,300 to $2,500.

A slab is the flat concrete you stand on. Block (concrete masonry units, stacked and mortared) is one common way to build the walls that hold the house up. Poured concrete is the other. People mix these up because both are “concrete,” but they do different jobs.

Block walls vs poured walls in an existing home

If your house already has block foundation walls, you cannot swap them for poured walls without tearing the house off the foundation. That is a rebuild, not a repair. The better question is whether your block wall is failing, and how we stabilize it.

Block walls fail along the mortar joints, usually from frost heave. Water in the disturbed backfill next to the house freezes, expands, and pushes the wall inward. That backfill is the looser fill the builder put back after digging, so it drains slowly and holds water. Cold winter plus wet fill puts pressure on the wall.

When a block wall bows or cracks, we have a few ways to hold it. Carbon-fiber straps lock a wall that is bowing in but still mostly straight, at $850 each with a 25-year wall stabilization warranty. A power brace handles a wall that has moved more and may need pulling back over time, at $1,300 per brace. Past that point we look at wall anchors or steel I-beams, priced after we see them, since the right call depends on how far it has gone.

A poured wall with a crack is a different repair. Most poured-wall cracks get crack injection, epoxy or polyurethane, at $1,000 to $3,000 with a 10-year warranty. A thin, stable crack does not need a brace. If it is weeping water and not moving, injection is the whole job.

When the problem is the footing under the wall

Sometimes the wall is fine and the ground under it gave out. The footing settles, and you get cracks that step or open at one end of the house. That is a piering job, not a wall job.

Helical piers screw down to stable soil and carry the load past the soft backfill. They run $2,700 per pier for the first three, then $2,200 per pier after that with a 25-year engineered warranty, and we install them in-house, no subs. Push piers do the same work on heavier loads. For a sinking corner, piers are the fix, and no amount of new block or slab patching solves it.

When it really is a slab question

If your concern is a cracked basement floor slab, that is mostly cosmetic and drainage, not structure. A slab crack rarely means the house is in trouble. What it can mean is water working up through the floor wall joint where slab meets wall.

If water is the real issue, you do not want a structural product at all. You want interior drainage. Our Forever Dry System is full-perimeter interior drainage plus a sump pump, a 12-mil wall vapor barrier, and a dehumidifier. It runs $3,000 to $30,000 and it is 100% guaranteed to be dry for life! We do not do exterior excavation waterproofing. In our field experience it fails in about two to three years, while interior drainage lasts.

You do not need every service on this page. Most homes need one, and a free inspection tells you which, and where you can leave things alone. Price comes down to the length of wall, how far it has moved, soil access, and how many piers or straps the job takes. We give you a number after we look, with a free estimate and quote within 24 hours.

A note on settling in our climate. The U.S. EPA and DOE building science resources both treat foundation moisture and frost as the main drivers of movement in cold regions like ours. See DOE Building America for the building science. For what your homeowners policy may cover, the Insurance Information Institute is a neutral starting point.

Want to know whether your wall, footing, or floor is the real problem? Call us at 603-610-1770 or book your free inspection. We will tell you plainly what it needs and what it does not.

See the matching hubs: structural and foundation repair, foundation repair, helical piers, supplemental support, basement waterproofing, and the 603 guarantee.

Related questions

Can you replace a block foundation wall with a poured one? On an existing home, that is a full rebuild, not a repair. We do repair work, so we stabilize the block wall you have with carbon-fiber straps at $850 each or a power brace at $1,300 per brace, and we price a full wall rebuild after we see it.

Are block foundation walls weaker than poured walls? Block walls fail at the mortar joints and bow under frost pressure, where poured walls tend to crack instead. Neither is doomed. Both have a stable repair path, and which one you have just changes the fix.

My basement floor slab is cracked. Is my foundation failing? Usually no. A floor slab crack is most often cosmetic. If water is coming up at the floor wall joint, that is a drainage job, and our Forever Dry System at $3,000 to $30,000 is the durable answer.

Do I need piers or wall straps? Piers fix a sinking footing. Straps and braces fix a bowing wall. They solve different problems, so the inspection tells you which one your house actually has.