What is the best way to seal foundation cracks from the inside in NB?

The best interior method for sealing foundation cracks in New Brunswick is polyurethane foam injection — it works on wet or actively leaking cracks, remains flexible after curing, and performs well through NB's freeze-thaw cycles. Epoxy injection is the second option for dry, dormant cracks where structural strength of the repair is the priority. Surface-applied waterproofing paints or cements applied over cracks without injection are generally the least reliable option for anything more than hairline surface cracks.

It is important to be clear about what interior crack sealing achieves: it addresses the symptom (water entering through a specific crack) without addressing the cause (hydrostatic pressure from exterior soil and water against the wall). In NB, where spring thaw generates significant water pressure against foundation walls — especially in Fredericton and Moncton where homes in the Saint John River and Petitcodiac River catchments deal with high water tables — interior crack injection is a practical repair for isolated cracks, but does not replace addressing poor exterior drainage.

Polyurethane foam injection for leaking cracks:

This method involves drilling injection ports along the crack at 6-12 inch intervals, inserting low-pressure injection ports into the drilled holes, and pumping two-component polyurethane that expands and cures within the crack. The foam is hydrophilic — it actively seeks out and reacts with moisture, expanding to fill voids and seal the crack path completely even while water is flowing through it. The cured foam remains flexible, which is important for NB foundations that experience slight seasonal movement from soil pressure and frost. Professional polyurethane injection costs $500-$1,500 per crack depending on length and severity.

Epoxy injection for dry structural cracks:

For dormant, completely dry cracks — particularly diagonal or vertical cracks that have not changed in years and show no active moisture — epoxy injection creates a bond stronger than the surrounding concrete. This is the right choice when structural integrity of the wall is the primary concern. Epoxy has no flexibility once cured, so it is not appropriate for cracks that are still moving or in locations subject to significant seasonal soil pressure variation. Professional epoxy injection runs $500-$1,000 per crack.

What not to do: Hydraulic cement pressed into a leaking crack is a temporary patch — it stops active water but does not penetrate and seal the crack depth, and the rigid plug can be bypassed by water pressure that redirects through adjacent concrete porosity. Interior waterproofing paints (Drylok, ZoneSeal) applied over cracks do not seal the crack itself — they create a coating on the wall surface that will eventually fail under continued hydrostatic pressure from NB's wet springs.

After any interior crack repair, improve exterior drainage: ensure downspouts extend at least 6 feet from the foundation, grade the soil to slope away from the wall, and if the same crack or adjacent cracks continue to leak in subsequent springs, have a professional assess whether exterior waterproofing (excavating to the footing and applying a proper exterior membrane with new weeping tile) is warranted. In NB, that is the permanent solution for chronically wet foundation walls.

New Brunswick Concrete can connect you with foundation crack repair specialists in Moncton, Fredericton, Saint John, Dieppe, Miramichi, Bathurst, and across the province.