Cracks in Your Walls — When to Worry, and When Not To
The short answer
Worry about wall cracks that are wider than 5mm, run diagonally or in stair-steps through brickwork, are wider at the top, keep growing, or come with sticking doors and sloping floors. Fine hairline cracks in plaster are usually cosmetic and not a structural concern.
A new crack in the wall is unsettling, but most are harmless. The trick is knowing which cracks are cosmetic and which are telling you the foundation is moving. Here is how to read them.
When to worry about cracks in walls
Width, direction and change over time are what matter. As a rough guide, hairline cracks under about 1mm are cosmetic, cracks of 5mm or more warrant a professional look, and anything you can fit a coin into is a clear warning sign. A crack that is stable has probably stopped moving; a crack that keeps growing has not.
- Hairline (under 1mm): usually cosmetic
- Fine (1–5mm): monitor and note if it grows
- Wide (5mm+): get it inspected
- Growing or coin-width: act promptly
What the shape and location tell you
Diagonal and stair-step cracks that run through the brickwork, especially near windows, doors and corners, point to foundation movement. Cracks that are wider at the top suggest one side of the house is dropping. Vertical cracks straight up a wall, and fine map-like cracks in render, are more often shrinkage and less concerning. Cracks that reopen after patching are a sign the movement is ongoing.
What causes structural wall cracks in Melbourne
The usual cause is reactive clay soil melbourne moving the footings, often made worse by drainage problems or trees. If the cracking comes with sticking doors foundation and sloping floors, the foundation is the likely culprit. The lasting fix is foundation repair melbourne that addresses the cause, not just filler in the crack.
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