What is the best repair method for a vertical foundation crack that leaks water in my Fredericton basement every spring?

The best repair for a vertical foundation crack leaking water every spring in Fredericton is a polyurethane injection from the interior, which seals the crack through the full thickness of the wall and remains flexible enough to handle seasonal movement. This is the industry-standard repair for poured concrete foundation cracks and typically costs $300 to $800 per crack — a straightforward fix that stops the water and lasts for the life of the foundation when done properly.

Vertical cracks in poured concrete foundations are almost always shrinkage cracks — they form as the concrete cures and contracts, usually within the first few years after construction. They are not structural concerns in most cases. However, in Fredericton, where the Saint John River valley brings a high seasonal water table and mixed clay-loam soils hold moisture against foundations, these cracks become active water entry points every spring. As the frost exits the ground between March and May and snowmelt saturates the soil, hydrostatic pressure pushes groundwater through any crack in the foundation. Even a hairline crack can deliver a surprising volume of water under pressure.

Polyurethane injection is preferred over epoxy injection for cracks that leak water. Here is why: polyurethane resin is injected into the crack under low pressure, where it reacts with moisture and expands to fill the entire crack from the interior face through to the exterior soil side. It cures as a flexible, waterproof foam that moves with the foundation through freeze-thaw and seasonal soil cycles without cracking or debonding. Epoxy, by contrast, cures rigid and hard — it bonds the crack faces together and restores structural strength, but in a climate like Fredericton's where the foundation experiences thermal movement and soil pressure changes throughout the year, rigid epoxy can crack adjacent to the repair, reopening the leak.

The injection process takes 1 to 2 hours per crack and is done from the interior, meaning no excavation is needed. A technician installs injection ports along the crack at intervals, applies a surface seal paste over the crack between ports, then injects the polyurethane resin through each port sequentially under controlled pressure. The resin travels through the full wall thickness and often visibly emerges on the exterior soil side, confirming complete penetration. After curing (usually 24 hours), the surface seal and ports are removed, leaving a smooth wall ready for finishing.

When Injection Is Not Enough

If the crack is in a concrete block wall rather than poured concrete, injection is not effective — block walls leak through mortar joints and hollow cores, not through a single crack. Block wall leaks require an interior drainage system. If the vertical crack is wider than 1/4 inch or shows signs of displacement (one side higher or further out than the other), have a structural engineer assess it before injecting — wide or displaced cracks may indicate settlement rather than simple shrinkage.

For Fredericton homeowners planning to finish their basement, fix all leaking cracks before any framing or insulation work. Discovering a leak after the drywall is up means tearing out finished walls to access the crack — far more expensive than the original repair. A professional crack injection specialist will typically guarantee the repair for 10 to 25 years. Get matched with a foundation repair contractor through New Brunswick Basements for a free assessment of your leaking cracks.

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Looking for experienced contractors? The New Brunswick Construction Network connects homeowners with qualified professionals:

• Thirty Four Renovations
• Gionetterenovations