Should I use epoxy injection or polyurethane injection to repair a poured concrete foundation crack in my Moncton basement?

For most poured concrete foundation cracks in Moncton basements, polyurethane injection is the better choice — it stays flexible, expands to fill the full crack depth, and tolerates the minor seasonal wall movement caused by Moncton's sandy and silty soils. Epoxy injection has its place too, but it is a rigid repair best suited for structurally significant cracks that need bonding strength rather than just water sealing.

The key difference comes down to flexibility versus rigidity. Polyurethane foam injection expands as it cures, filling voids and irregular crack paths all the way through the wall thickness. Once cured, it remains slightly flexible, which matters in Moncton where the sandy soils can shift subtly under footings and where the freeze-thaw cycle (frost depth around 1.2 metres in the Moncton area) causes minor seasonal movement in foundation walls. A rigid epoxy repair can re-crack alongside the original if the wall moves even slightly, sending you back to square one. Polyurethane absorbs that movement without breaking its seal.

Epoxy injection welds the crack shut with a structural bond that restores much of the concrete's original tensile strength. This makes it the right choice when a structural engineer has identified a crack that needs to be bonded back together — for example, a crack near a lally column bearing point or at a corner where the wall carries concentrated load. Epoxy does not expand, so it must be injected under pressure into a crack that is relatively clean and dry at the time of injection. In Moncton, where spring thaw sends the water table rising through March to May, timing an epoxy injection during a dry period can be challenging. Polyurethane, by contrast, actually reacts with water to expand and cure, making it effective even in actively leaking cracks.

Cost comparison is similar for both methods: expect $300-$800 per crack in the Moncton market, depending on crack length and accessibility. A typical basement might have two to four shrinkage cracks, putting total repair cost at $600-$3,200. Both methods are injected from the interior, so no exterior excavation is needed — a major advantage over exterior membrane repairs.

For Moncton homeowners planning to finish their basement, here is the practical guidance: if your poured concrete wall has hairline to moderate shrinkage cracks (under 6mm wide) that are leaking or damp, polyurethane injection is the standard recommended repair. It seals the water out, stays flexible through seasonal movement, and the repair is typically warrantied for 10-25 years by reputable NB foundation companies. If a crack is wider than 6mm, runs horizontally, or shows signs of structural displacement (one side offset from the other), get a structural assessment before any injection — you may need reinforcement beyond what either injection method provides.

One important note: injection repairs address individual cracks in poured concrete walls only. They are not suitable for concrete block foundations, which are common in older Moncton homes — block walls leak through the mortar joints and hollow cores, requiring a different waterproofing approach entirely. Make sure your contractor correctly identifies your foundation type before recommending a repair method.

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

• Thirty Four Renovations
• Gionetterenovations