Cracks in walls sit in a strange spot: most of them mean nothing, a few of them mean the ground is winning, and to a worried homeowner they all look the same at 11pm. This checker sorts them the way an inspector would — by width, pattern, location and behaviour — and gives you a straight answer, including "relax, monitor it".
The logic comes from how crack damage is actually classified in Australia. The residential footings standard (AS 2870) and CSIRO homeowner guidance grade cracks largely by width: under 1mm is negligible-to-slight and usually cosmetic; 1–5mm is the "watch it" band where the trend matters more than the number; past 5mm you're into the range where assessment is warranted and repairs get structural. Pattern refines the read — vertical hairlines are the least concerning, diagonal cracks running off door and window corners mean the frame is racking, and stepped, staircase-shaped cracks through external brick mortar are the classic signature of footing movement.
Behaviour is the tiebreaker. Reactive clay soils across regional Victoria and Queensland swell each wet winter and shrink each dry summer, so plenty of cracks simply breathe with the seasons — annoying, not dangerous. A crack that ratchets wider every year, by contrast, is a process that doesn't stop on its own. Answer the seven questions honestly and we'll tell you which story your walls are telling — and, because the right fix depends on whether your house stands on stumps or a slab, we'll point you at the right next step, not a generic sales pitch.
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