How do I fix cracks in my garage foundation caused by NB frost heave?

Fixing cracks caused by frost heave in your garage foundation depends entirely on the severity — hairline cracks under 1/4 inch can be sealed with flexible polyurethane caulk or hydraulic cement, but cracks wider than 1/4 inch, cracks that are actively growing, or cracks accompanied by wall displacement indicate ongoing structural movement that requires professional assessment before any repair is attempted. Frost heave is the most common cause of garage foundation damage in New Brunswick, where the frost line extends 4 to 5 feet below grade and the freeze-thaw cycle exerts enormous force on any foundation that does not extend below that depth.

Before repairing any crack, you need to understand why it formed. In NB, frost heave cracks typically fall into two categories. The first is one-time settlement or shrinkage cracking — these are hairline cracks that appeared within the first year or two after construction, have not grown or changed since, and show no vertical or horizontal displacement on either side. These are cosmetic and can be repaired with confidence that they will not return. The second category is active frost heave cracking — these cracks grow wider each winter, may partially close each summer, and are often accompanied by visible displacement where one side of the crack is higher or further in or out than the other. Active cracks indicate that the foundation is still moving, meaning the frost is reaching under or behind the footing and lifting the structure. Repairing the crack without addressing the cause is pointless — the repair will crack again the next winter.

For cosmetic or stable cracks (under 1/4 inch, no movement), the repair process is straightforward. Clean the crack thoroughly with a wire brush and shop vacuum to remove loose concrete, dust, and debris. For cracks in foundation walls, apply a flexible polyurethane crack sealant (such as Sikaflex or Loctite PL Concrete) using a caulk gun. The flexibility is important because concrete continues to expand and contract with temperature changes — rigid fillers like standard hydraulic cement will crack again. For cracks in the garage slab floor, use a concrete crack filler specifically designed for floors, applied slightly below the surface and then topped with a self-levelling sealant for a smooth finish. Materials cost $10-$30 per crack, and the repair takes 15 to 30 minutes per crack.

For wider cracks (1/4 to 1/2 inch) in foundation walls that are stable (not actively growing), a two-part epoxy injection system provides a structural repair that bonds the concrete back together and seals the crack against water infiltration. Epoxy injection kits are available for $30-$80 and include injection ports, epoxy paste for surface sealing, and the injectable epoxy resin. This is a moderate DIY project — the key is patience, as the epoxy must be injected slowly from the bottom up to ensure complete filling of the crack without air pockets.

For active frost heave damage — cracks wider than 1/2 inch, walls that are visibly bowed or displaced, or a slab that has heaved unevenly — you need a professional foundation contractor to assess the situation. The underlying cause must be addressed, which typically means one or more of the following: excavating and extending the footing below the frost line if it was originally built too shallow, improving drainage around the foundation to reduce the moisture available for frost formation, or installing rigid foam insulation on the exterior of the foundation to keep frost from penetrating to the footing depth. These are significant repairs costing anywhere from $3,000-$15,000 depending on the extent of the problem, but they are the only way to stop the cycle of heave and damage.

A critical warning for NB homeowners: if your garage was built on a shallow foundation — less than 4 feet deep in southern NB or less than 5 feet in northern areas — frost heave damage will continue and worsen every year until the foundation issue is properly addressed. Cosmetic crack repairs on a moving foundation are a waste of money. Have a foundation professional assess the depth and condition of your footings before investing in repairs. Find contractors through the New Brunswick Construction Network at newbrunswickconstructionnetwork.com.