A leaking crack in a poured-concrete wall is usually the cheapest waterproofing problem you'll ever fix — if it's done right. Warrantied epoxy and polyurethane injection, $400–$1,000 per crack, most repairs completed in a few hours.
Get a Free Quote 📞 Same-Day Assessment — Call NowMost Guelph homes built from the 1970s onward — and virtually everything in newer subdivisions in the south end, Kortright Hills, Westminster Woods and the East End — sit on poured-concrete foundations. Poured concrete shrinks as it cures, and shrinkage cracks are close to inevitable: thin vertical or diagonal lines that often run down from a basement window corner, a beam pocket, or a spot where the wall steps down. They're rarely a structural emergency. But because a crack passes through the full thickness of the wall, it's a direct pipeline for groundwater the moment the soil outside is saturated.
Crack injection repairs that pipeline from the inside, without excavation. We surface-seal the crack, set injection ports along its length, and pump a liquid resin under pressure so it travels through the entire crack — from the inside face of the wall to the soil side — and cures into a solid, watertight seal. No digging, no landscaping damage, no jackhammering. A typical single-crack repair takes two to four hours and the basement is usable the same day.
The two injection materials do different jobs, and a contractor who quotes without explaining the difference is worth a second opinion.
In practice, the large majority of leaking basement cracks we see in Guelph get flexible polyurethane. Where there's a structural concern, we'll say so and price the epoxy or reinforcement work honestly.
Homeowners often tell us the same story: the crack has been there for years, bone dry — then every spring, or after one big summer thunderstorm, there's a wet line down the wall. That's not the crack changing. It's the soil. Much of Guelph sits on clay-heavy till that drains slowly and holds water against the foundation. Through winter, frost drives moisture cycles in the upper soil; when the March–April melt arrives — often on top of still-frozen ground that can't absorb it — hydrostatic pressure against the wall spikes, and water finds the one path through: your crack. The same physics repeat during heavy summer downpours. A crack that leaks once will leak again; each wet cycle also carries dissolved minerals that leave the white efflorescence staining you may already see.
We're direct about this because it's where homeowners get burned. Injection is the complete, permanent fix when you have a typical shrinkage crack in an otherwise sound poured wall: roughly vertical or diagonal, hairline to a few millimetres wide, not offset, not growing. That describes most of the cracks we repair, and it's why the fix costs hundreds rather than thousands.
Injection is not the whole answer when the crack is a symptom of something bigger: horizontal cracking mid-wall (a classic sign of soil pressure on the outside), stair-step patterns near corners, cracks wider at the top than the bottom (settlement), one face of the crack offset from the other, or a wall that's visibly bowing. It's also the wrong tool entirely for concrete block and stone foundations, which leak through cores and mortar joints rather than discrete cracks — those homes need exterior waterproofing or an interior drainage system with a sump pump. If your crack signals movement or your foundation isn't poured concrete, we'll tell you at the assessment, explain the options, and quote them separately — no pressure, no upsell theatre.
Per our 2026 Guelph waterproofing cost guide, expect $400–$1,000 per crack. The main variables are crack length (a full-height 8-ft crack takes more ports and resin than a 3-ft window-corner crack), wall thickness, and access — a finished basement where drywall must be opened along the crack adds scope. Multiple cracks injected in one visit are cheaper per crack. Every injection repair is warrantied, and because we can usually assess a crack the same day you call, a leak spotted in the morning is often sealed before the next rain.
Related services: Sump Pump Installation · Exterior Waterproofing · 2026 Cost Guide
Assessments — leaks don't wait, neither do we
Honest per-crack pricing, quoted before we start
Most single-crack repairs done in one short visit
Injection repairs backed in writing
Most single-crack repairs cost $400 to $1,000 per crack, depending on crack length, wall thickness and access. Multiple cracks repaired in one visit are usually priced lower per crack.
Polyurethane is the standard for actively leaking cracks — it reacts with water, expands, and stays flexible as the wall moves seasonally. Epoxy is a structural adhesive for restoring wall strength but needs a dry crack. Most leaking Guelph basement cracks call for polyurethane.
Freeze-thaw cycles and Guelph's clay-heavy soil. Snowmelt and spring rain saturate the clay, hydrostatic pressure builds against the wall, and a crack that's dry all summer leaks every March and April.
For a typical shrinkage crack in a poured wall, yes — the resin fills the crack through the wall's full thickness and the repair is warrantied. If the crack is driven by ongoing movement, injection alone treats the symptom, which is why we diagnose the cause first.
No. Injection only suits solid poured-concrete walls. Block and stone foundations leak through cores and mortar joints and need interior drainage or exterior waterproofing instead.
Tell us where the crack is and whether it's leaking now — we'll book a same-day assessment when we can and give you a firm per-crack price.
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