Visible indicators documented during inspection, crack patterns, visual-inspection limitations regarding structural significance, and when structural engineering expertise is recommended. Educational page — not engineering expertise or legal advice.
A foundation crack is a visible discontinuity in the foundation wall, concrete slab, or load-bearing masonry. All homes develop cracks over time — this is generally normal and linked to concrete shrinkage, freeze-thaw cycles, and natural soil movement. The question is therefore not "are there cracks?" but "which cracks are concerning and which are not?". During a visual inspection, we document the crack pattern (vertical, horizontal, diagonal, stair-step), its measured width, its length, its orientation, signs of activity or stabilization, and any associated displacement or infiltration. These observations let us propose the most plausible hypotheses, but confirming the activity and cause often requires specialist verification.
Here are the crack patterns we regularly document in residential inspection, with a general indication of typical concern. This classification is educational — each crack must be evaluated in its context by an inspector, then by a structural engineer when signs warrant it.
Narrow vertical crack (less than 1 mm), often centred, caused by normal concrete shrinkage during curing. Common in foundations less than 10 years old. To monitor for infiltration or widening.
Wider vertical crack (1-5 mm) or one that widens over time. May indicate differential settlement on one side of the building. Verification recommended if infiltration or active widening.
Crack running horizontally across the foundation wall, particularly at mid-height. Possible indicator of active lateral soil pressure against the wall (wet backfill surcharge, frost-thaw, roots). Structural engineering expertise recommended.
Crack following mortar joints in a stair-step pattern in masonry or concrete blocks. Often associated with differential settlement or movement of the underlying foundation. Width and activity documented.
Diagonal crack starting from the corner of a window, door or change of section. Often linked to a concentration of structural stress or localized settlement. To be considered with other movement signs.
Multiple converging or star-pattern cracks on the basement or garage concrete slab. In areas and periods where pyrite has been documented (Laval, South Shore, North Shore — 1985-95), to consider in the pyrite-risk context and possibly with petrographic analysis.
Important: this classification is educational and does not replace in-person evaluation. The same pattern can be benign in one context and concerning in another, depending on building age, foundation type, soil, history, and associated signs (infiltration, displacement, door-frame deformation). Our report documents observed cracks and recommends, on a case-by-case basis, specialist verification when signs warrant it.
Our visual inspection follows the InterNACHI standard. For foundation cracks specifically, there are important limitations to understand.
We recommend structural engineering expertise in the following situations — ideally before removing the conditions on the purchase offer.
Foundation cracks occur in all regions, but typical causes vary by geology, construction period, and foundation type.
If the pre-purchase inspection reveals concerning cracks and the condition-removal deadline is short, several options are available depending on your risk tolerance and the seller's cooperation.
What is documented during an inspection, what is not, and when to consult an engineer.
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