Construction Problem Center
Cracks in Walls: Causes & When to Worry
Hairline cracks are common in most buildings, but not all cracks mean the same thing. Understanding the pattern helps you know whether it's cosmetic or structural.
Common causes
- Normal drying shrinkage in new plaster or blockwork
- Thermal movement — expansion and contraction with temperature
- Foundation settlement, especially on expansive or poorly compacted soils
- Overloading of a wall not designed to carry the load above it
- Poor mortar mix ratios or workmanship during construction
- Movement around openings (doors, windows) without adequate lintels
Most fine, vertical hairline cracks under 1–2mm are cosmetic.
- • Cracks wider than 5mm, or growing over weeks
- • Diagonal cracks running from corners of doors and windows
- • Cracks that appear on both the inside and outside of the same wall
- • Cracks accompanied by doors/windows that no longer close properly
This information is general guidance for planning purposes and is not a substitute for an in-person professional assessment. Every building and site is different — a TEKEEY engineer can confirm the actual cause and recommend next steps.
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A TEKEEY engineer will visit, assess the issue, and recommend next steps.
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