October is the right time to look at your foundation. Not because the cracks appeared in October — they have probably been there since spring — but because what happens between now and March will determine whether a manageable repair becomes a major one.
Ontario’s freeze-thaw cycle is relentless. Water enters a crack, freezes overnight, expands, and widens the opening. By the time the ground thaws in April, a crack that was hairline in autumn can be measurably larger. Do this for three or four winters without intervention and you have a structural problem where you once had a surface one. The time to act is before the ground freezes.
Not All Cracks Are Equal
Walk your basement and look at every wall carefully. The type, location and direction of a crack tells you a great deal about what is causing it and how urgently it needs attention.
Vertical cracks running straight up and down the wall are the most common. They typically form as concrete cures and shrinks over time. Many are stable and have been the same size for years. The concern is when they show staining, mineral deposits, or active moisture — signs that water is using the crack as an entry point.
Horizontal cracks are a different matter. A horizontal crack running across a basement wall signals lateral pressure — the soil outside pushing inward against the foundation. This is a structural warning that requires professional assessment, not monitoring. Do not wait on a horizontal crack.
Diagonal cracks, particularly in corners, often indicate differential settlement — one section of the foundation moving at a different rate than another. These can be stable or active. Measure them and check back in a month. If the crack has grown, get it assessed.
Stair-step cracks in block or brick foundations follow the mortar joints in a stair pattern. These typically indicate movement or settlement and are worth having a professional examine.
“Most homeowners assume foundation cracks are purely a structural issue, but the real risk before winter is water,” says Andrew from Aquatech Waterproofing Hamilton. “Every crack is an open door for moisture. Once that water freezes inside the wall, it expands with enough force to turn a minor crack into a serious problem by spring. The repairs we do in October cost a fraction of what we fix in April.”
What to Do Right Now
Check every crack for active moisture. Press a piece of dry tissue against the crack and hold it there for ten seconds. If it picks up moisture, water is actively moving through. This crack needs sealing before winter.
Mark stable cracks with pencil. Draw a line across both sides of the crack and write today’s date beside it. Check it again in four weeks. A crack that has not moved is a very different problem from one that is actively growing.
Look at the outside too. Walk around your home’s perimeter and check where the ground slopes. Soil that slopes toward the foundation directs every rainstorm and snowmelt event directly against your basement walls. Re-grading the soil away from the house is one of the most cost-effective things you can do before winter.
Check your downspouts. A downspout that discharges at the foundation deposits hundreds of litres of roof water against your basement wall every storm. Extend it at least six feet away from the house before the snow arrives.
Clear window wells. Remove any debris, leaves, or standing water from window wells before the first frost. A window well that fills with ice can push directly against the window frame and crack it.
When to Call a Professional
Call a licensed waterproofing contractor if you find any of the following: a horizontal crack of any length, a crack that has grown since you last measured it, active moisture coming through any crack, white powder on the wall near a crack, or any crack wider than the thickness of a debit card.
Epoxy and polyurethane injection — the standard professional repair for active foundation cracks — seals the crack from the inside permanently and can be done year-round. The cost for a single crack repair is a few hundred dollars. The cost of leaving it through another Ontario winter is considerably more.
Take an hour this weekend to walk your basement, check your cracks, and look at your exterior drainage. If anything concerns you, get a professional opinion before the ground freezes. The window for low-cost intervention closes every year around the same time — and it is closing now.
