Not all cracks mean the same thing. The pattern, direction, and location of a crack tell you what is happening behind the finish — and whether you are looking at a cosmetic touch-up or an envelope failure that is quietly wetting your sheathing. This guide is how we assess exterior walls across the Greater Toronto Area before we quote anything.
Owners usually ask how wide a crack has to be before it matters. That is the wrong first question. A 0.2 mm crack directly under a failed window flashing will do far more damage than a 1 mm shrinkage crack in the middle of a sheltered panel, because the first one sits on an active water path and the second one does not.
An exterior wall is a system: a drainage plane, insulation, a reinforced base coat, and a finish. Cracking is the system telling you which layer is under stress. Read the pattern first, then measure.
Severity here is a triage guide, not a substitute for opening the wall. Two walls with identical surface cracking can have very different conditions behind them.
The right call when the substrate is sound and the cracking is confined — corner cracks, an isolated impact point, a single failed joint. The work is genuine repair, not filler: open the crack, re-establish reinforcing mesh across it, rebuild the base coat, then blend the finish texture so the patch is not a visible scar.
Appropriate when the assembly is performing but the surface is tired, chalking, faded, or finely crazed across a wide area. This is also the moment to correct the sealant joints, because fresh finish over failed caulking just buys a season. A re-coat is a surface decision — it does not fix drainage or flashing, and it should never be used to bury an active leak.
Necessary when the problem is behind the finish rather than in it: saturated insulation board, deteriorated sheathing, a barrier-type assembly with no drainage path, or repeated failures in the same location. Replacing an elevation is a larger number up front, but paying three times to re-repair a wall that keeps getting wet costs more and leaves the underlying damage progressing the whole time.
Southern Ontario swings across the freezing point repeatedly through winter and shoulder seasons rather than staying frozen. Water that has entered a crack expands each time it freezes, widening the crack a little more on every cycle. This is why a hairline crack ignored in November is a real one by April.
The lower metre of a wall near driveways, walkways, and parking takes salt spray all winter. Salt accelerates finish breakdown and shows up as efflorescence and spalling at grade — which is why base details and termination heights matter so much here.
A dark elevation in July and the same wall in January can differ by more than 60 °C at the surface. The assembly expands and contracts through that range, and expansion joints are what let it do so without tearing. Undersized or omitted joints are one of the most common causes of straight-line cracking we find.
Rain arriving horizontally finds gaps that vertical rain never touches — window perimeters, penetrations, terminations. A wall that is dry in an ordinary shower can leak in a storm, which is why leaks are so often reported as intermittent and dismissed as something else.
The more of this you have ready, the more accurate any contractor’s assessment will be — including ours.
Send us photographs and we will tell you what we think is happening before anyone quotes a scope. If it is cosmetic, we will say so.
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