Foundation crack repair

Is it a water problem or a structure problem

Most cracks in poured foundations are shrinkage cracks: thin, roughly vertical and stable. They matter only if they leak. Cracks that are wider than a pencil line and growing, horizontal cracks in block walls, stair-step cracks through mortar joints, and walls that lean or bow inward can point to soil pressure or settlement. On hillside lots, the uphill wall carries more soil and water pressure, so watch it closely. Structural signs call for an engineer or foundation specialist before any waterproofing work.

How the repair works

For a leaking crack in poured concrete, the contractor cleans the wall, glues injection ports along the crack, seals the surface between them and then pumps in material from the bottom up until it comes out the next port. Flexible polyurethane is common for leaks because it expands into the crack and tolerates small movement. Rigid epoxy is used when the goal is to bond the concrete back together. After curing, the surface seal and ports can be ground off.

Gaps around pipes and wires that pass through the wall, and old form-tie holes in poured walls, are sealed in much the same way.

• Clean and inspect the crack
• Set ports and seal the surface
• Inject from the bottom up
• Let it cure, then finish the surface

Stone and block walls

Injection is made for poured concrete. Stone and block walls leak through mortar joints and hollow cores rather than single cracks, so injecting one spot rarely helps. For those walls, repointing the joints and adding drainage are the usual answers. If you have an older stone foundation, mention it in your request so the right contractor follows up.

Keeping the repair working

A sealed crack lasts longest when the pressure behind it is reduced. Clean gutters, extend downspouts, keep soil sloping away and check for water coming down the hill toward the house. If new cracks keep appearing, ask whether drainage or a structural issue is the real cause.

Keep a record

Before any repair, photograph each crack with a tape measure beside it and write down the date. If you want to watch a crack for movement, pencil a mark at each end and check it every few months. That history helps a contractor or engineer judge whether a crack is stable, and it is useful paperwork when you sell. After the repair, keep the invoice and warranty with your house records.

If you are buying a home in the area, ask the seller about past crack repairs and any warranty that transfers.

Typical crack and foundation repair costs

Published national figures. Not quotes.

National figures, rounded, not quotes. The two crack ranges come from different sources and show how much prices vary.

Sources: This Old House, basement waterproofing cost; Fixr, foundation repair