What is the best crack sealing method for a leaking basement wall in a Fredericton home built in the 1970s?

The best crack sealing method depends entirely on your foundation type — a 1970s Fredericton home most likely has either a poured concrete or concrete block foundation, and these require completely different repair approaches.

First, identify what you are working with. Walk around the outside of your home and look at the exposed foundation above grade. Poured concrete is smooth with a uniform surface, and cracks will appear as defined lines, usually vertical or diagonal. Concrete block (also called cinder block or CMU) has visible horizontal mortar joints between rectangular blocks. Many Fredericton homes built in the 1970s used concrete block, though poured concrete became more common toward the end of that decade.

Poured Concrete Foundation Cracks

For poured concrete walls, polyurethane crack injection is the best repair method for active leaks. A technician drills small injection ports along the crack, then injects flexible polyurethane resin under pressure. The resin fills the entire crack from the interior face through to the exterior, expanding on contact with water to form a waterproof seal. Polyurethane remains flexible after curing, which is critical in Fredericton — the freeze-thaw cycles along the Saint John River valley cause foundations to shift slightly each season, and a rigid repair will crack again. Cost: $300 to $800 per crack depending on length and accessibility.

Epoxy injection is the other option for poured concrete. Epoxy creates a structural bond that is stronger than the original concrete, making it the right choice for cracks that indicate structural movement (horizontal cracks, cracks wider than 1/4 inch, or stair-step patterns). However, epoxy is rigid and can crack again with seasonal movement. For a non-structural, leaking shrinkage crack — which is what most 1970s poured concrete cracks are — polyurethane is the better choice.

Concrete Block Foundation Cracks

Crack injection does not work on concrete block walls. The blocks are hollow, and injected material fills the void inside one block rather than sealing the water path through the wall. Leaking block foundations in Fredericton need a different strategy.

The most common and effective approach is an interior waterproofing system: a drainage channel along the base of the wall that collects water seeping through the blocks and routes it to a sump pump. This manages the water rather than trying to seal every porous block and mortar joint — which is impractical on a 50-year-old block wall. Cost: $3,000 to $8,000 for a full interior drainage and sump pump system.

For exterior repair on block walls, a contractor excavates to the footing, applies a waterproof membrane or coating to the outside of the block wall, and installs new weeping tile. This stops water from entering the blocks in the first place. Cost: $8,000 to $20,000 depending on perimeter length and depth. This is ideal but expensive.

Fredericton-Specific Considerations

Fredericton's mixed clay and loam soils in the Saint John River valley hold water against foundations, and the seasonal water table fluctuation is significant — especially in low-lying neighbourhoods near the river. A crack that barely weeps in August can pour water in April during spring thaw. Any crack repair should be assessed during or just after the wet season to understand the full severity.

For a 1970s home, also check for efflorescence (white mineral deposits) on the wall surface near the crack. This indicates chronic water migration through the concrete, which means the crack has been leaking for a long time and the surrounding concrete may be deteriorated.

Do not attempt crack injection as a DIY project — proper injection requires professional equipment and experience to ensure the resin fills the entire crack depth, not just the surface. A surface-only seal will trap water inside the wall where it freezes and expands, making the crack worse. Have a waterproofing professional assess the crack, determine if it is structural or cosmetic, and recommend the right repair. New Brunswick Basements can connect you with experienced foundation repair contractors in Fredericton for a free assessment.

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

• Thirty Four Renovations
• Gionetterenovations