Crazing
Crazing is a fine network of surface cracks in cement render or concrete, caused by rapid drying, over-trowelling or a cement-rich mix. Not structural.
Ask Chalkline about this →Crazing is a network of fine, shallow surface cracks in cement render, concrete, or mortar, typically forming a hexagonal or irregular pattern across the finished face. The cracks are usually less than 0.2 mm wide and do not penetrate the full depth of the render coat. Crazing is a cosmetic defect, not a structural failure, but it provides pathways for moisture ingress and can allow efflorescence or early deterioration of the surface if left unsealed.
The most common causes in residential render are: applying coats that are too thick in a single lift (excess shrinkage on drying), using a cement-rich mix without sufficient lime or sand (rigid, brittle surface), over-trowelling the finish coat (brings cement laitance and water to the surface, which then shrinks), and drying too rapidly from sun or wind before the render has set. Preventing crazing requires correct mix ratios, working coats within the recommended thickness limits, shading in hot weather, and misting with water during the initial cure period.
Also known as: map cracking, shrinkage cracking (surface), alligator cracking (surface).
Category: Render and plastering defects
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Last updated: 2026-05-10. Verified: 2026-05-10. Quarterly review for currency.