Repairs & Maintenance · 7 min read · Beginner
How to Fill Small Wall Cracks Before Decorating
Prepare and fill small stable cosmetic cracks neatly, while recognising when recurring, widening or moisture-related cracking needs investigation instead.
Key points & steps
- Check that the crack is suitable for a cosmetic repair. Cracks that are widening, repeatedly returning, stepped through masonry, associated with bulging or accompanied by damp should be investigated first.
- Protect the surrounding area and scrape away loose paint, filler or friable plaster so the repair edges are sound.
- Open a very fine stable crack slightly only where appropriate for the chosen filler, creating enough clean surface for the repair material to bond rather than leaving a dusty hairline.
- Brush or vacuum out dust and prepare the surface in accordance with the filler instructions; very absorbent backgrounds may need controlled priming or dampening.
- Press a suitable interior wall filler firmly into the crack with a filling knife and remove obvious voids rather than merely skimming across the surface.
- Smooth the repair flush or slightly proud as appropriate, feathering the edges onto the sound wall.
- Allow the filler to dry fully, then sand lightly until the repair blends with the surrounding surface without hollowing the centre.
- Prime or spot-seal the repaired area if required by the paint system before redecorating, and investigate the cause if the crack returns.
Practical tips
- Do not fill over loose plaster, active damp or moving cracks and expect a lasting result.
- Use filler appropriate to the crack width and depth rather than one product for every defect.
- Wear suitable dust protection when sanding and control dust around occupied rooms.
What you may need
- Scraper
- Filling knife
- Suitable wall filler
- Dust brush or vacuum
- Fine abrasive paper
- Primer or paint system as required
- PPE