Foundation crack repair cost

Injecting a foundation crack costs $350 to $1,000, typically around $600. Epoxy runs $350 to $800 for a dry structural crack and polyurethane $400 to $1,000 for one that is actively leaking.

That is the cheap end of foundation work, and for most cracks it is the right and sufficient answer. The expensive question is not what the injection costs. It is whether the crack is the whole problem or a symptom of something moving.

What each method costs

Epoxy is a structural adhesive. It is stronger than the concrete around it and it welds the two sides back into one piece. It is rigid, so it only belongs in a crack that is not going to move again.

Polyurethane foams and expands to fill irregular voids, and it stays flexible. It is the default for a leaking crack, because it chases the water path and tolerates a little movement. It seals; it does not restore strength.

Choosing epoxy for a moving crack means the concrete cracks again beside the repair. Choosing polyurethane for a structural crack means the leak stops and the weakness remains.

Reading the crack

Vertical or near-vertical, hairline, in a poured wall. Almost always shrinkage from the original cure. Extremely common and structurally meaningless. Seal it if it leaks.

Vertical, wider at the top or bottom. One end of the wall has settled more than the other. Worth measuring over a season.

Diagonal, from a corner of a window or door opening. Stress concentration. Usually settlement, and the width tells you how much.

Stair-step through the mortar of a block or brick wall. Settlement in block construction. Common, and the question is again width and movement.

Horizontal, running along a course partway up the wall. The serious one. Soil pressure pushing the wall inward, usually with some bowing. This is not an injection job; it needs an engineer and probably reinforcement.

Cracks in the floor slab. Usually shrinkage and usually harmless, unless there is a height difference between the two sides.

Measure before you spend

The width matters, and so does whether it changes.

Under an eighth of an inch and static: monitor. An eighth to a quarter: seal it, keep watching. Over a quarter inch, or any crack where one side sits proud of the other, or any horizontal crack: get an engineer before getting a quote.

To monitor, mark each end of the crack with a pencil line and the date, and either measure the width with a feeler gauge or fit a plastic crack monitor from a hardware store for about $15. Check monthly for six months, through at least one wet and one dry period.

A crack that has not moved through a full seasonal cycle is a crack you can seal and forget. That $15 gauge is the best value in foundation work.

Doing it yourself

DIY injection kits are $50 to $150 and they work, for the right crack.

They are reasonable on a hairline to eighth-inch vertical crack in a poured concrete wall that is not leaking under pressure. They are not reasonable on a block wall, where there is no single crack path to inject into; on a leaking crack with active water, which needs to be injected under pressure while wet; or on anything horizontal.

The failure mode of a bad DIY injection is not wasted money. It is a sealed crack that hides continuing movement for two years.

The part injection does not fix

An injection restores or seals the concrete. It does nothing about whatever moved the wall, and if that is still happening the crack comes back, usually beside the repair.

Before or alongside any crack repair, deal with the water. Downspouts discharging six to ten feet from the house, gutters clear, ground sloping away six inches over the first ten feet, and window wells drained. These cost a few hundred dollars and they are the reason a large share of cracks appeared.

If the crack is structural rather than shrinkage, the underlying cause is settlement, and settlement is corrected by underpinning, not by filling the gap it left.

Frequently asked questions

How long does an injection last?

Permanently, on a crack that is not moving. The repair is stronger than the surrounding concrete. On a crack that continues to move, it fails, which is diagnostic in itself.

Can a crack be repaired from inside if it leaks from outside?

Yes, and polyurethane injection is done from the inside precisely for that reason. It fills the crack through the full wall thickness rather than just skinning the surface, which is why it works where surface patching does not.

Should I be worried about a crack in my slab floor?

Usually not. Slabs crack from shrinkage as a matter of course. Worry if one side is higher than the other, if it is wider than a quarter inch, or if it is growing.

My house is new. Should it have cracks?

Small ones, yes, and most appear in the first two years as the concrete cures and the backfill settles. Check whether the builder's warranty covers them; many cover structural cracks above a specified width for up to ten years.

How much should an engineer cost?

$400 to $1,500 for an inspection and a written report. On any crack you are unsure about, it is the cheapest thing you can buy, because it is the only opinion in this process from someone who is not selling the repair.