Every poured concrete foundation cracks. Concrete shrinks as it cures and it has essentially no tensile strength, so it relieves that stress by cracking. Finding a crack in your basement wall is not, by itself, information.
What matters is which kind. Here is how we triage them, so you can do a first pass before anyone quotes you five figures.
Read the pattern, not the width
| What you see | What it usually means | What to do |
|---|---|---|
| Vertical or near-vertical, under 3mm, uniform width | Shrinkage crack. Very common, especially in the first years. | Repair only if it leaks |
| Vertical, noticeably wider at one end | Some differential settlement | Monitor, then assess |
| Diagonal from the corner of a window or door | Settlement concentrating stress at an opening | Assess |
| Horizontal, across the middle of a wall | Lateral soil pressure bowing the wall inward | Get it looked at now |
| Stair-stepping through block mortar joints | Differential settlement in a block wall | Get it looked at now |
| Any crack with displacement — one side proud of the other | Movement, not shrinkage | Get it looked at now |
| Fine map-like cracking across the surface | Surface crazing. Cosmetic. | Nothing |
| Crack at a cold joint where two pours meet | Common and usually benign, but a frequent leak path | Repair if it leaks |
The three bolded rows are the ones that justify urgency. Everything else is a leak question rather than a structural one.
Why horizontal cracks are the serious one
A vertical crack means the wall shrank or settled slightly. The wall is still doing its job.
A horizontal crack across the middle of a wall means something is pushing the wall inward and the wall is bending. The mid-height point is where bending stress is highest, which is why it appears there.
What pushes: saturated soil is heavy and exerts lateral pressure. Clay soils — present in a good deal of Barrie ground — expand when they take up water and contract when they dry, cycling that pressure seasonally. Frost also does it: water in soil against a foundation freezes and expands, and Simcoe County frost goes to about 1.2 metres.
A bowing wall does not straighten out on its own, and the failure mode at the end of that process is not gradual. If you have a horizontal crack in a block wall, particularly with any visible inward displacement, this is the one item on this page that warrants a call this week rather than this season.
Monitoring a crack properly
If someone has told you to watch a crack, do it with a method rather than a memory.
- Mark both ends of the crack with a pencil line across it, and write the date beside it.
- Measure the width at three points and write the numbers on the wall.
- Photograph it with a ruler or a coin in frame, in the same light, monthly.
- Note the season. Almost every foundation crack widens slightly in spring and closes in late summer, and that seasonal cycling is normal.
What is not normal: growth that continues in one direction over more than one annual cycle, any width increase beyond about 1mm within a season, or the appearance of displacement between the two faces.
Six months of this data is worth more than any single inspection, and it costs nothing.
Polyurethane or epoxy
Both are injected through ports set along the crack from inside. They do different jobs.
Polyurethane expands on contact with moisture and remains flexible. It seals against water and tolerates the small seasonal movement every foundation has. This is correct for a non-structural crack that leaks — the large majority.
Epoxy is rigid and bonds the concrete back into a single monolithic piece, restoring structural strength. Correct when the crack is structural and the wall needs to act as one piece again. It is also unforgiving: if the wall moves again, the new crack appears beside the repair rather than in it.
A contractor who uses the same product on every crack is choosing based on what is in the van.
What injection does not do
Injection seals the crack. It does not address why the wall cracked.
If the cause is a downspout discharging against the foundation, or clay soil cycling wet and dry against the wall, or a footing bearing partly on disturbed fill, then either the crack returns or a new one appears nearby. This is why any competent crack visit includes a look at the outside — grade, downspouts, window wells, what is planted against the wall.
Often enough that exterior look is the actual fix, and the injection is just the cleanup.
Cost in Barrie
| Job | Typical cost |
|---|---|
| Polyurethane injection, single crack under 2.4 m | $350–$600 |
| Epoxy structural injection, single crack | $550–$900 |
| Additional cracks, same visit | $250–$450 each |
| Carbon fibre straps for a bowing wall | $550–$850 per strap |
| Steel beam bracing, per beam | $700–$1,200 |
| Independent structural engineer’s report | $800–$1,800 |
| Exterior excavation where injection is insufficient | $180–$320 per foot |
Get an independent engineer for structural work
If a contractor tells you a wall is structurally compromised, get a structural engineer’s assessment from someone who is not selling the repair.
This is not a comment on anyone’s honesty. It is that “diagnose the structural problem” and “sell the fix for it” should not be the same person’s incentive, and a written engineer’s report also gives you something to hand a buyer, an insurer, or a second contractor.
For non-structural leaking cracks, this is unnecessary — that is a straightforward repair with a straightforward price.
When a crack is genuinely nothing
We are asked to look at a lot of cracks that need nothing at all:
- A hairline vertical crack in a ten-year-old poured wall, dry, uniform width. Normal.
- Surface crazing that looks like a dry lakebed. Cosmetic, entirely.
- A crack at a cold joint that has never been wet. Leave it.
- A crack that has been there since the house was built, marked and monitored, and has not moved in three years. That is a stable crack, and stable is the outcome you were hoping for.
If you have one of those and someone has quoted you a foundation system, get a second opinion before you do anything.