Almost every house has cracks somewhere, and most of them are harmless. Hairline cracks in plasterboard or render (under about 1 mm) are usually caused by normal thermal movement and seasonal moisture changes, and are considered negligible under AS 2870.
Cracks worth monitoring are those from 1–5 mm — often at window and door corners — particularly if doors and windows start to stick. Cracks above 5 mm, stepped cracking through brickwork, cracks that keep growing, or walls and floors going noticeably out of level are the point at which a structural engineer should take a look.
The cause matters more than the crack itself. Reactive clay movement, poor drainage, tree roots drying out the soil, leaking pipes and inadequate footings all produce different patterns, and the right fix depends on a correct diagnosis. Cosmetic patching without addressing the cause simply moves the crack to next season.
Our structural inspection reports identify the cause and severity of cracking and give you a clear, prioritised path to rectification — which is often far less drastic (and less expensive) than owners fear.