Are hairline cracks in walls normal?
Usually, yes. Plaster and render shrink as they dry, and different materials expand and contract differently with temperature. HDB attributes cracks along the joints between block walls and concrete elements to this differential movement and recommends repainting hairline cracks with a flexible sealant or elastomeric paint. A hairline crack that is stable, not widening, not recurring after proper repair and not in a beam, column or slab is generally cosmetic.
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.
More questions on this topic
- What crack width is considered structural?
- Which cracks should I worry about?
- How do I monitor a crack?
- Who repairs cracks in a condominium?
- Can I fill cracks myself before selling or renting out?
- Do cracks in a new home fall under the developer's defects liability?
- Does the Periodic Structural Inspection look at cracks?