Through the wall · the slow leak

Foundation crack repair: why a basement wall leaks, what it costs, and why insurance usually says no

When a basement is wet and it is not a sewer backup or a burst pipe, the water came through the floor or the wall, and a crack is the usual suspect. Cracks form over time, as the federal guidance puts it, and a crack that has been dry for years can start to weep the spring the water table rises.

This page covers what the federal guidance says you can fix yourself and when it says to call someone, what two companies publish as their prices, why a crack has to be dealt with before a basement is finished, and the insurance problem: water that seeps through a foundation is on GIO’s short list of typical exclusions, and the cover written for it is optional.

The repair methods, and what the quote calls them

Why a crack starts leaking

The federal page makes two separate points, and they explain why a crack can be dry for years. Rain and snowmelt reach a crack from the surface, so grading and downspouts decide how much water arrives at it. Groundwater reaches it from below when the water table is high, which is seasonal: spring melt and long wet spells. A crack is a path; the water has to get to it first.

Toronto’s two categories are worth using as a test before you price a repair. Water seeping through a wall or a floor crack after rain is the first category — drainage. Water rising out of a floor drain is the second — a sewer backup, which no crack repair will touch. If you are not sure which you had, the basement flooding page separates them.

What you can fix yourself, and what you should not

The federal method for a small crack is short: dry it completely, brush out old caulking or sealant, vacuum, wipe, fill, then seal. Then watch it. The page asks you to mark the ends of each crack in pencil and look again, so that a crack that is growing tells you so, and to check the foundation at least once a year and again after heavy rain or snowmelt if you have just sealed one.

The professional list is where the money is, and each item points to a different problem. A crack that keeps growing is movement, not water. A large network of cracks is the wall, not one defect. A crack where water is coming through is a leak whose source may be outside, where only excavation reaches it — the federal page warns that some foundation damage cannot be seen without internal or external excavation. It also says to check with your local government about permits and inspections for foundation repairs, which matters most for the structural work.

What it costs, where anyone publishes it

No Canadian public body publishes a crack repair price, and this site does not invent an average. Two companies publish their own figures, reproduced here as theirs, from two provinces.

The two exterior figures overlap but do not match, and the reason is scope: how deep the crack runs, what is in the way of the excavator, and whether the quote includes the membrane and the backfill. The bands are also a warning about diagnosis. An injection is a few hundred dollars and a structural repair is thousands; the first question is whether the crack is leaking or moving. Ask any company quoting the work which one they think it is and why, and whether a permit is needed.

When the leak is not one crack but the whole wall — a wall that weeps along its length, or a footing drain that has failed — the job becomes drainage rather than crack repair, and the prices and municipal programmes are on the weeping tile and sump pump pages. In Toronto, two companies' published per-foot prices for whole-wall waterproofing are set beside the City's subsidy and permit rules on basement waterproofing in Toronto.

Before you finish the basement

Natural Resources Canada’s warning is blunt for a reason: insulation and drywall over a damp wall hide the water and give it something to rot. Its sequence is the useful one — fix major leaks first, deal with minor ones by sloping the grade and aiming downspouts at least two metres away from the foundation, patch from the inside, and only then insulate. The dampness symptoms it lists are the ones to look for before you build: staining or mould, blistering and peeling paint, efflorescence, spalling and a musty smell. The federal foundation page adds bubbling or discoloured paint and wallpaper to the same list.

If a finished basement is already wet, Health Canada’s timeline applies: mould begins within 48 hours where moisture is excessive, and the mould removal page sets out what it says about cleaning it.

What insurance does with water through a crack

Slow seepage through a foundation is close to the definition of what a home policy is not for: gradual, repeated, and connected to the condition of the house. GIO’s published cases show how it is argued:

The cover that is written for water coming through a wall is a separate, optional one, and not every insurer sells it.

Read GIO’s definition closely: it is for water that enters “suddenly and accidentally” through the foundation. A crack that has wept every spring is the opposite. Whatever your policy says about the water damage, the crack itself is the house’s repair. The full comparison is on ground water coverage.

Questions people actually ask

Where to read next

• Weeping tile, when the whole wall leaks
• Ground water coverage
• Basement flooding
• Sump pumps
• Mould after water damage