Call promptly if a crack is actively widening, has appeared suddenly, is wider than about 5mm, or is accompanied by doors and windows that no longer close properly, uneven floors, or similar signs elsewhere in the building. Call at a less urgent pace, but still call, if you're planning to buy or sell the property and want an independent opinion before you commit either way. For everything else, hairline cracking that's been stable for a long time with no other symptoms, ongoing monitoring is usually a reasonable approach.
The Practical Checklist
- Get it looked at promptly if the crack is growing, appeared within the last few weeks, follows the diagonal stepped pattern described in our piece on diagonal cracking in brick walls, or is accompanied by doors and windows that have started binding.
- Get it looked at before making a decision if you're buying, selling, or about to start renovation work nearby, since the cost of a proper inspection is small next to the cost of getting the decision wrong.
- Monitor for now if the crack is fine, hairline, hasn't changed in the time you've owned the property, and nothing else in the house is showing signs of movement. Photographing it against a ruler every few months is a simple way to track whether it's actually stable.
What Actually Happens on the Call
A structural assessment is a visual, non-intrusive inspection, typically including a review of the crack pattern, its extent and distribution around the building, and where useful, a floor level survey. The engineer forms an opinion on likely cause with reference to the relevant Australian Standard, most commonly AS 2870 for footing-related movement, and provides that opinion in a written report you can act on, whether that's simply monitoring, arranging remedial works, or supporting an insurance or dispute process.
Why Timing Matters
Waiting too long on active movement can mean a manageable issue becomes a more expensive one, and can also make it harder to establish cause once other contributing factors (further seasonal movement, additional works nearby, general wear) have had time to muddy the picture. On the other hand, most cracking genuinely doesn't need an engineer at all, so the goal isn't to treat every hairline crack as an emergency, it's knowing which ones actually warrant the call. See our broader guide on whether a crack is actually structural for the fuller framework behind this checklist.
