Foundation crack: what it is, how serious, what it costs

Concrete shrinks a little as it cures, mostly in the first years. Since it cannot shrink freely, it cracks: that is a shrinkage crack, thin, often vertical, often near a corner or under a basement window. A large share of poured concrete foundations have some.

Other cracks come from movement: settling soil, frost, the push of the earth against the wall. A French report says « fissure de fondation », with words like « mineure » (minor), « à surveiller » (to monitor), « colmatée » (already sealed) or « expertise recommandée » (engineer recommended).

A thin, vertical, dry crack with no offset is generally shrinkage: you seal it so it does not let water in, and you keep an eye on it. What should worry you: a horizontal or stair-step crack, wider at one end than the other, one side offset from the other, water coming in, or doors that stick and floors that slope inside the house.

That is why it shows up in all three lists: “Can wait” for a minor crack to seal, “To check” when it is hidden by finishes or was already repaired, “Fix first” when the inspector asks for an engineer.

Sealing a crack, most often by injection from inside: $500 to $1,500 for one isolated crack, $1,200 to $3,000 for several cracks on the same wall. Having the crack assessed by a structural engineer: $600 to $1,600.

If the engineer finds the foundation is moving, the fix is priced separately, after their report.

These are ballpark figures for Quebec, to be confirmed with quotes.

1. Is the crack vertical, horizontal or stair-step, and how wide is it?
2. Is one side offset from the other, and are there water marks?
3. Did you see other signs of movement: doors that stick, floors that slope, cracks above the windows?

Ask the seller whether the crack was already repaired, and for the invoices: some injection companies give a warranty that stays with the house.

Does your report mention a foundation crack? Upload it: in five minutes, I tell you what comes first, what to have checked and what to ask the seller.

Not for a thin, vertical crack that gets sealed. Yes when the inspector recommends it, when the crack is horizontal, stair-step or offset, or when it keeps widening. In Quebec, an engineer is a member of the Ordre des ingénieurs du Québec.

Mark both ends with a pencil line and the date, then look at it over the seasons. A crack that grows longer or wider should be seen by an engineer.