You found a crack in your foundation. Now you want to know if it’s serious. The answer depends almost entirely on what type of crack it is. Not the age of the house, not recent weather, not whether it looks wide or narrow at first glance. Start there.
What Type of Foundation Crack Do You Have? (Start Here)
There are five main crack types in BC residential foundations. Our article on the types of foundation cracks covers the full diagnostic picture. Here’s the working version.
Hairline cracks are thin, sometimes web-like cracks in poured concrete. They’re usually caused by concrete curing shrinkage and are common in homes built between the 1970s and 1990s. Stable, dry, and unchanged over time, they’re almost always cosmetic.
Vertical cracks run top-to-bottom, sometimes at a slight angle. Most are caused by differential settlement. A small vertical crack that hasn’t moved in years is often low priority. One that’s grown noticeably in recent months, or one with moisture present, needs attention.
Horizontal cracks run side to side, particularly in block or poured walls. These indicate lateral soil pressure pushing against the wall from outside. Treat every horizontal crack as structural until a professional says otherwise.
Stair-step cracks follow the mortar joints in block or brick foundations, stepping diagonally. They’re usually settlement-related, and both the direction and the width matter. A narrow stair-step crack in an otherwise stable wall is a different situation from one that has widened over the past year.
Diagonal cracks often run from a corner or penetration point in the wall. In BC homes, differential settlement is the usual cause.
In BC, clay soils expand with rain and contract in dry summers. That movement is why many cracks appear seasonally. They open in summer and close in winter. That seasonal behaviour doesn’t make them harmless; it just adds context.
How to Fix Foundation Cracks: The DIY vs Professional Question
For some crack types, DIY is a reasonable starting point. For others, it isn’t, and the distinction matters.
What a homeowner can reasonably address:
A hairline crack in poured concrete, stable and dry, with no sign of change over the past several months, is a fair candidate for a surface treatment from a hardware store. Polyurethane or epoxy injection kits are widely available. These are surface seals, not structural repairs. They can keep moisture out temporarily, but they don’t restore tensile strength and won’t help if the crack is still moving.
What requires a professional:
- Any horizontal crack in a block or poured wall
- Any crack that has changed noticeably over the past few months
- Any crack accompanied by moisture or staining
- Cracks wider than 6mm
- Stair-step cracks in block or brick foundations
- Any crack where one side of the wall sits slightly higher or lower than the other
Wet basements in this region often start at existing cracks. A DIY seal might stop water temporarily, but if soil pressure or poor drainage is the underlying cause, the crack will work around the seal, or the wall will show problems somewhere else. The seal treats the symptom. A professional assessment addresses what’s behind it. For basement-specific concerns, cracks in basement walls is worth reading before reaching for the sealant. And for a clear breakdown of which crack types cross into structural territory, structural foundation cracks covers the distinction directly.
The three-tier framework for how to respond:
Relax: Hairline crack, stable, poured concrete, no moisture. This is almost certainly curing shrinkage and doesn’t need immediate action.
Monitor: A vertical crack under 6mm with no moisture present. Photograph it quarterly, note any changes in width or length, and track it over time.
Call Now: Any horizontal crack, any crack with moisture, any crack that has grown noticeably, or any crack over 6mm wide.
How Foundation Crack Repair Works (What Professionals Actually Do)
When a professional assesses and repairs a foundation crack, the method depends on the crack type, its cause, and whether it’s still moving. The five main approaches:
Epoxy injection is used for structural cracks in poured concrete. Epoxy is injected under pressure, fills the crack fully, and restores tensile strength to the wall. It’s rigid, which works well for a dormant crack but is the wrong choice for one that’s still moving.
Polyurethane injection is the go-to where water intrusion is the main concern. Unlike epoxy, polyurethane expands as it cures and stays slightly flexible. It seals against water but doesn’t restore structural integrity.
For horizontal cracks or walls showing signs of bowing, carbon fiber reinforcement is the typical approach. Straps are bonded to the wall surface to restrain further inward movement. They hold the wall where it is. They don’t fix what’s pushing on it from outside.
Foundation underpinning is the answer when the crack is caused by settlement rather than simple wall movement. Sealing a crack that’s opening because the foundation is moving is a temporary measure at best. Foundation underpinning using steel piles addresses the movement itself.
Sometimes the right repair is outside the wall entirely. When hydrostatic pressure or poor grading is what’s driving the crack, drainage remediation is the fix. Foundation repair options covers the full range if you want to go deeper.
One note on active vs dormant cracks: an active crack, one still in motion, needs a flexible repair. A dormant crack can be rigidly filled. Getting that distinction wrong leads to repairs that fail early.
Epoxy injection restores strength to a poured concrete wall, but if the foundation is still settling, the crack will return. Sometimes in the same place, sometimes nearby. The crack is a symptom, not the whole problem.
How to Fix Foundation Cracks: Reading the Pattern in BC Homes
In BC, the fix and the cause are connected. The soil here creates crack patterns you won’t always find explained in a generic guide, and knowing which conditions apply to your property changes how you read what you’re seeing.
Surrey homeowners deal with one of the most common crack-causing conditions in the region: clay soil. Clay in Surrey, South Surrey, and surrounding neighbourhoods expands significantly when wet and contracts through dry summers. That cycle puts stress on foundation walls year over year. Many cracks in Surrey homes follow this seasonal pattern, opening slightly in summer and closing again through fall and winter.
Pre-1950 concrete in older Vancouver character homes behaves differently from modern poured walls. Older concrete was mixed with different aggregate ratios and responds to movement in its own way. Cracks in heritage foundations often need more careful interpretation to understand what they’re actually indicating.
Richmond and Delta properties sit on soft delta soils that compress unevenly over time. Settlement in these areas tends to be gradual and long-term, and cracks often reflect slow, ongoing movement rather than a single event.
Slope-adjacent homes in North Vancouver, Maple Ridge, and West Vancouver face a different problem: lateral soil pressure from uphill. Horizontal cracks in these homes are often driven by soil pushing against the uphill side of the foundation.
To tell whether a crack is active or dormant, a pencil line drawn across the crack at its widest point, dated and photographed, is a practical starting point. Check it every few weeks. If the crack has grown past the mark, it’s active. No change over six months points toward dormant.
When a Foundation Crack Is a Symptom of Something Bigger
Some homeowners notice a crack and, once they start paying attention, realise there’s more happening. Foundation cracks don’t always develop alone. Often they’re part of a cluster of settlement signs that together tell a clearer story than any one crack does.
Watch for cracks appearing alongside:
- Sticking doors and windows, particularly doors that changed gradually over months rather than all at once
- Uneven floors, especially a slope or noticeable bounce that’s new or noticeably worse than before
- Cracks at the base of a chimney, or a chimney that’s pulling slightly away from the main structure
- Active water intrusion through or near the crack itself
- Multiple cracks appearing in the same section of the foundation over a short period
A single hairline crack isn’t usually the story. When a homeowner notices a crack in the foundation wall and then remembers the doors started sticking six months ago, that timeline matters.
If the combination of what you’re seeing raises questions, when to worry about a foundation crack covers the warning threshold in more detail.
What to Expect From a Foundation Crack Assessment in BC
A free assessment with Ossum covers more than just the crack itself.
The assessment starts with a visual inspection of the crack, including its pattern, width, and length, along with a look at the surrounding area. Secondary signs get attention too: moisture staining, adjacent cracks, and how level the floors are nearby.
You’ll be asked about the crack’s history. When did you first notice it? Has it changed? Did anything else in the house change around the same time? That timeline matters more than many homeowners expect.
The findings are documented in writing, and you’ll get a clear explanation of what was observed and what it likely means.
One thing to know going in: an assessment doesn’t always end with a repair recommendation. Often the outcome is “keep an eye on this.” That’s a useful answer. Knowing a crack is stable gives you real information about your house, even if nothing needs to be fixed right now.
