How do I know if my foundation crack in my NB home is structural?

Not all foundation cracks are structural emergencies, but in New Brunswick's freeze-thaw climate, any crack that is growing, wide, or accompanied by water infiltration deserves immediate professional attention. The distinction between a cosmetic crack and a structural one can have major consequences for your home's safety and value.

Cracks that are likely cosmetic include thin hairline cracks (under 1/16 inch wide) running vertically or at a slight diagonal in a poured concrete foundation — these are usually shrinkage cracks that formed during the initial curing process. Poured concrete shrinks slightly as it cures, and vertical hairline cracks are common on foundations in Moncton, Fredericton, Saint John, and throughout NB. They typically appear within the first year or two of construction and remain stable.

Cracks that warrant professional assessment include horizontal cracks running along the length of a foundation wall, which are the most serious type — they indicate lateral soil pressure or frost heave pushing the wall inward. Stair-step cracks in block or masonry foundations, diagonal cracks radiating from corners of windows or door openings, and cracks wider than 1/4 inch all require professional evaluation. Any crack that is getting wider over time — even slowly — is a structural warning sign.

New Brunswick's climate makes this especially important. Our 150+ freeze-thaw cycles per year force water into existing cracks, where it expands by 9% when frozen. A small crack that could have been injected for $500-$1,500 can widen into a serious structural problem over two or three NB winters if left untreated. Spring thaw is when NB homeowners most often notice foundation problems, as saturated soil increases hydrostatic pressure against basement walls.

Practical steps for assessment: Look at the crack from both inside and outside the foundation if accessible. Mark the ends of a crack with pencil lines and dates to monitor whether it is growing. Note if the crack lets water in during or after rain, or during spring snowmelt. If the crack is accompanied by bowing or tilting of the wall, that is a structural emergency — call a structural engineer immediately.

Foundation issues should never be diagnosed or repaired without professional assessment. A structural engineer or experienced foundation contractor can determine whether crack injection is sufficient or whether underpinning, wall anchors, or excavation and waterproofing are needed. New Brunswick Concrete can connect you with local foundation contractors who can assess your situation.