Structural crack assessment

Most foundation cracks are boring. A vertical hairline in a poured wall is shrinkage, it has been there since the house was a year old, and the worst it does is let water in. A minority are not boring, and the point of an assessment is to tell you quickly and without drama which category you are in, before you spend money on the wrong repair.

What a crack's shape tells you. Vertical and hairline, often slightly wider at the top, is the classic shrinkage crack. Diagonal cracks running from the corner of a window or a beam pocket usually indicate some settlement, which may be old and finished or may be ongoing. Stair-step cracking through the mortar joints of a block wall suggests differential movement. A horizontal crack partway up a wall is the one to take seriously, because it often means lateral pressure from soil or ice pushing the wall inward. Width matters too: a crack wider than about 6 mm deserves a closer look regardless of direction.

Step one: the walk-round. A proper assessment starts outside. Grading that falls toward the house, downspouts discharging at the foundation, a window well full of leaves, a driveway that has heaved against the wall, a tree whose roots are drawing water out of clay in a dry August. Many Ottawa cracks have a cause visible from the driveway.

Step two: measuring and recording. Each significant crack is measured for width at several points, photographed with a scale in frame, and its ends marked and dated. That record is what makes a second visit meaningful.

Step three: reading the rest of the house. Cracks in a wall are one data point. Doors and windows that stick or have been planed, sloping floors, drywall cracking at door corners upstairs, gaps opening at trim, a chimney separating from a wall. Movement in a foundation shows up throughout a house, and a foundation contractor who never leaves the basement is not assessing your house.

Step four: monitoring, where the answer is not yet obvious. A crack monitor is a simple gauge fixed across the crack that shows movement to a fraction of a millimetre. Pencil marks with dates work almost as well. Ottawa's seasons make this especially worthwhile, because a crack that opens in the dry weeks of late summer and closes in a wet spring is behaving differently from one that widens steadily.

Step five: the recommendation, in writing. Three possible outcomes. Seal it, because it is non-structural and the issue is water. Repair it as part of a drainage or waterproofing scope. Or refer it to a licensed professional engineer, because it needs a design rather than a product.

How long it takes. An assessment visit is typically 45 to 90 minutes. A written report follows within a few days. Monitoring, if recommended, generally runs across at least one full seasonal cycle, so six to twelve months, which is why starting the marks now rather than next spring is worth doing even if you do nothing else.

What it costs in Ottawa in 2026. Indicative ranges. A contractor assessment visit is commonly free to about $250, and frequently credited against the repair if you proceed. A structural engineer's inspection and letter typically runs $500 to $1,500, and a full report with drawings for a remedial design costs more. Those engineer fees are separate from any contractor quote. A crack monitor is under $50 and you can fit it yourself.

What makes an Ottawa house different. Champlain Sea clay is sensitive material: it swells when wet, shrinks in drought and can lose much of its strength when disturbed (NRC, Geotechnical properties of Leda clay in the Ottawa area). A dry summer followed by a wet autumn can move a foundation here in ways it would not move on sand or rock. Frost adds the second mechanism, which is why the Building Code sets foundation depths as deep as 1.2 m in clay (OBC 9.12.2.2), and why a shallow addition, a porch or a garage slab poured at the wrong depth is a common source of cracking where it meets the original house. Neighbourhood matters as well: 1950s and 1960s Alta Vista and Elmvale block foundations, 1970s and 1980s Nepean and Orleans poured walls, and Barrhaven and Riverside South houses of the last twenty-five years all show their own typical patterns.

Who should do the work, and when you need an engineer. Assessment by a foundation contractor is unlicensed work, and a free one from a company that also sells the repair carries an obvious incentive. For anything horizontal, bowing, stepped in block, wider than roughly 6 mm, or actively moving, the person you want is a professional engineer. Structural design in Ontario is regulated, and you can verify a licence in the PEO directory. An engineer sells you a conclusion rather than a product, which is precisely the value.

What to ask. Is this crack structural, and what specifically makes you say so. Will you give me that in writing. Do you sell the repair you are recommending. What happens if I do nothing for a year. Should I be monitoring, and how. If you think an engineer is needed, will you work to their design. A contractor willing to say that a crack needs nothing at all is usually the one worth calling back.