How do I monitor a crack?

Answer

Mark the crack ends with a pencil line and the date, photograph it with a ruler or crack-width card, and record the widest point. For better data, fix a two-part plastic tell-tale gauge across the crack and read it regularly. A crack that does not change over several months, including through hot and wet seasons, is likely stable; one that keeps opening is active and needs an engineer.

From the RRD Field Guide, checked against the sources cited in Cracks in Walls, Beams and Ceilings in Singapore: Which Are Structural and When to Worry. General information, not advice for your project.

The fuller picture

Most hairline cracks in plaster, paint and at wall-to-beam joints are non-structural, caused by shrinkage and thermal movement. Worry when cracks are wide or widening, diagonal or stepped, tapered, recurring, accompanied by rust stains, sagging or sticking doors, or appear in beams, columns or slabs. Monitor with dated tell-tales and call a Professional Engineer for those signs.

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Key facts

Commonest crack in Singapore homes: Along joints between block walls and concrete beams or columns, from differential thermal movement
BCA PSI template: minor RC crack: Under 2 mm wide and under 30 mm deep
BRE damage categories 0 to 2: Cracks up to about 5 mm: aesthetic, redecoration only (low-rise masonry)
PSI cycle: Every 10 years (residential) or 5 years (other buildings)
Strata common property: Foundations, beams, columns and slabs (excluding underlayment)

Defects and maintenance

Popped tiles, cracks, spalling concrete, roof and inter-floor leaks, window and glass safety, and the exterior features owners are legally responsible for: what causes them, when they are dangerous, and who has to fix them.

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Planning works like this?

RRD surveys the site, lists cost risks before you sign and plans the approvals first.

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How do I monitor a crack?

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