What causes foundation cracks in New Brunswick homes?

Foundation cracks in New Brunswick homes are caused primarily by three forces: frost heave, hydrostatic water pressure, and concrete shrinkage during curing. All three are common in NB, and the type and pattern of cracking tells a lot about the underlying cause.

Shrinkage cracks are the most benign and extremely common. Nearly all poured concrete foundations develop hairline shrinkage cracks within the first year or two as the concrete cures and minor settlement occurs. These are typically vertical or slightly diagonal, uniform in width (under 1/8 inch), and not actively leaking. They are normal and, in most cases, do not indicate structural distress. Epoxy or polyurethane injection seals them if they're allowing moisture entry.

Frost heave and differential settlement create the most concerning cracks. When footings are inadequate — either not deep enough below NB's 4-foot frost line or bearing on soft or organic soil — the foundation moves unevenly with the seasons. This creates diagonal cracks running at 45 degrees from corners, stair-step cracks in block foundations, or horizontal cracks in poured walls. Diagonal cracks that are wider at the top than bottom indicate the footing is heaving at one end. This pattern requires professional structural assessment — it's not a DIY crack fill scenario.

Horizontal cracks in foundation walls are the most serious and require immediate professional evaluation. They indicate lateral soil pressure — the weight and moisture pressure of the surrounding soil is pushing the wall inward. This is common in Saint John and Fredericton where many older homes have unreinforced or lightly reinforced foundations that are now at or near their lateral load capacity. A horizontal crack that runs the length of the wall at mid-height, or that is wider in the centre than the ends, indicates structural distress requiring engineered repair, not cosmetic patching.

NB's spring thaw is the peak stress period for foundation cracks. Frozen soil thaws from the surface down, trapping melt water in a saturated zone against the foundation. The combination of soil pressure, hydrostatic pressure, and freeze-thaw cycling at the concrete surface accounts for most of the new crack activity that NB homeowners notice each spring.

If you're seeing new or growing cracks in your foundation, have a professional assess them before water damage, mould, or structural deterioration progresses. New Brunswick Concrete can connect you with foundation assessment and repair professionals through the New Brunswick Construction Network.