Cracks in interior plaster walls are common in New Zealand homes, especially in older villas, bungalows, and renovated properties across Auckland. Some are only cosmetic, while others can point to movement, moisture, or a poor previous repair.
The right fix depends on the type of crack. If you understand what caused it first, you can choose the best repair method and avoid the crack showing through the paint again.
First, work out what kind of crack you have
Before you grab filler, take a close look at the crack. Hairline cracks are often caused by normal house movement, seasonal changes, or shrinkage in old plaster. Wider cracks, cracks that keep reappearing, or cracks near windows and doors may need more than a simple patch.
Check whether the plaster feels sound around the crack. If the wall is soft, crumbling, damp, or bulging, the problem may be deeper than the surface. In that case, repairing and repainting over it will not last.
- Hairline crack: often repairable with flexible filler or joint compound
- Small open crack: may need widening slightly before filling
- Recurring crack: may need taping and a proper skim repair
- Crack with staining or softness: inspect for moisture or substrate damage
How to repair a small plaster crack
For a fine, stable crack, start by cleaning out any dust or loose material with a scraper, brush, or vacuum. If the edges are sharp or flaky, lightly open the crack a little so the filler can bond properly. This sounds counterintuitive, but a tiny V-shaped gap often gives a better result than trying to skim over a hairline line.
Use a suitable flexible filler or interior plaster repair compound and press it firmly into the crack. Smooth it flush, then let it dry fully before sanding lightly. If the crack sits on a joint, or if you know the wall has moved before, a tape repair is often better than filler alone.
A good finish usually depends on the prep as much as the repair itself. Dust off the area, spot prime if needed, then repaint with quality interior paint so the sheen matches the surrounding wall.
- Remove loose plaster and dust
- Widen the crack slightly if needed for adhesion
- Fill with the right repair compound
- Sand smooth once dry
- Prime and repaint the patched area
When the crack needs a stronger repair
If the crack is wider, active, or in a line where the wall joins another surface, you may need to reinforce it with fibreglass tape or paper tape before applying compound. This helps bridge the crack and reduce the chance of it coming back through the paint.
Cracks in older plaster walls can also hide previous patching, loose sections, or movement in the framing. In those cases, the surface may need to be cut back, resecured, and rebuilt properly before it can be painted. If there is any sign of moisture, that issue should be sorted first, otherwise the repair will fail.
When to call Steve
If you are unsure what is causing the crack, or you want a clean repair that will hold up under paint, it is worth getting advice from Steve, a Kiwi and a trade-qualified painter. He can assess whether the crack is cosmetic, structural, or moisture-related, then recommend the right plaster repair and prep before painting.
That is especially useful in premium Auckland homes where finish quality matters. For cracked plaster in bedrooms, living rooms, hallways, or ceilings, Steve can help get the surface properly repaired, blended, and ready for a smooth repaint.
Frequently Asked Questions
Can I just paint over a crack in plaster?
You can, but it is usually not a lasting fix. The crack may show through the paint again unless it is filled, reinforced, and properly prepared first.
What is the best filler for interior plaster cracks?
A flexible interior crack filler or plaster repair compound is usually best for small stable cracks. If the crack is on a joint or keeps returning, tape and compound may be better.
How do I know if a plaster crack is serious?
If the crack is widening, keeps reappearing, has staining, or the plaster feels soft or loose, it may indicate movement or moisture and should be checked before repainting.
Need a hand with your project?
Happy to tackle some of it yourself? Great — but for anything you’d rather leave to a professional, Steve Lunjevich is a Kiwi and a trade-qualified painter with 20+ years’ experience. Call or email for honest advice or a free, no-obligation quote.