Does a house built on a slab have to be anchor bolted to its foundation?

Yes. A house on a slab needs the wood sill plate fastened down to the concrete, and anchor bolts are the standard way to do it. Building codes have called for this for decades. The bolts tie the framing to the foundation so wind and movement can’t slide the house off its slab.

That’s the short version. Here’s what it means for your home.

When a slab gets poured, anchor bolts (sometimes called J-bolts) get set into the wet concrete around the edge. Once it cures, the bottom wood plate of your wall, the sill plate, drops over those bolts and gets washered and nutted down tight. Some builders use steel hold-down straps or powder-driven fasteners instead. The point is the same. The frame and the concrete have to act as one piece.

Why does code care? Lateral force. Wind pushing on a wall, ground settling, the house wanting to shift. Without that connection the framing can walk off the foundation over time. The anchor bolts stop that.

If your slab home was built in the last 40 years or so, it almost certainly has them already. You usually can’t see the bolts because drywall and trim cover the sill. So the real question most people are asking us is different. They’re asking whether something is wrong down there. A crack. A gap at the base of a wall. A door that won’t latch right anymore.

That’s where we come in.

What we fix on slab and foundation homes

We don’t pour new foundations or build new homes. We do repair. So if you’re worried about your slab or your foundation walls, here’s the kind of work that’s on the table.

Cracks in a poured foundation or slab edge get sealed with crack injection, epoxy or polyurethane. That runs $1,000 to $3,000 and carries a 10-year warranty.

If a wall is bowing or shifting inward, we stabilize it. Carbon-fiber straps lock a wall in place and come with a 25-year warranty. Pricing on those is $850 each. For a wall that needs more push, a power brace runs $1,300 per brace.

When a foundation is settling, sinking on one side, dragging a slab or a wall down with it, we lift and support it on helical piers. We drive those ourselves, in-house. They carry a 25-year engineered warranty and run $2,700 per pier for the first three, then $2,200 per pier after that.

Sagging floors over a crawl or basement get lally columns or floor support posts, $1,300 to $2,500, with a 10-year warranty. A rotted sill or beam gets replaced, $7,000 to $40,000. If a wall is failing and needs a new partner wall built inside it, that’s an auxiliary wall, about $1,350 per linear foot.

A few jobs we won’t price over the phone. A full foundation-wall rebuild, wall anchors, or steel I-beams. We price that after we see it. Same with anything involving a brand-new foundation, since that’s new construction and not what we do.

You can read more on the structural and foundation repair hub, or go straight to helical piers, sill replacement, or supplemental support.

When you don’t need us yet

Plenty of slab cracks are nothing. Concrete shrinks as it cures and hairline cracks come with the territory. A thin crack that isn’t moving, isn’t leaking, and isn’t tied to a door or window sticking is usually cosmetic. You don’t need a repair for that yet. Keep an eye on it. Mark the end of the crack with a pencil and a date. If it grows, call us.

What does deserve a look: a crack wider than a credit card, a crack that steps or stairs diagonally, a wall pushing inward, floors going out of level, or new gaps where the wall meets the slab. Here in New Hampshire, frost is the usual suspect. Water sits in the disturbed backfill soil around the foundation, freezes, and frost heave pushes against the walls. That pressure is what cracks and bows them over the years.

If water is also getting in, that’s a separate fix. A wet basement is interior drainage, our Forever Dry System, not a foundation repair. A damp crawl is crawlspace encapsulation. We’ll tell you which problem you actually have.

Every structural fix we do is backed by the 603 guarantee. We’re licensed and insured, BBB A+ accredited, and trusted by 5,000+ homeowners across New England with a 4.9 rating across 250 Google reviews.

Want eyes on it?

If you’ve got a crack, a gap, or a floor that feels off, get it looked at before it grows. Call us at 603-610-1770 or book your free inspection. Free inspection, free estimate, and a quote within 24 hours. We serve New Hampshire, Maine, and Massachusetts.

Related questions

Can you see the anchor bolts in a finished house? Usually not. The bolts sit in the sill plate at the very bottom of the wall, and drywall, baseboard, and flooring cover them. On an unfinished garage or an exposed slab edge you can sometimes spot the nuts and washers along the base.

Is a crack at the bottom of my slab wall serious? It depends. A hairline crack that isn’t moving or leaking is often just shrinkage. A crack wider than a credit card, one that’s growing, or one paired with a sticking door or an out-of-level floor is worth a free inspection. We seal active cracks with crack injection from $1,000 to $3,000.

Does a slab foundation settle like a basement does? It can. A slab can sink or tilt when the soil under it gives way, and that pulls the framing with it. We lift and hold settling foundations on helical piers, $2,700 per pier for the first three, then $2,200 per pier after that, with a 25-year engineered warranty.

Do you build new slab foundations? No. We’re a repair crew. We fix cracks, stabilize walls, lift settling foundations, and replace rotted sills and beams. New foundations and new builds are outside what we do.