How to Fix Cracked Wall Plaster

Cracks in plaster are very common in UK homes. Most are cosmetic and easily repaired yourself. Some require professional attention.

Likely causes

• Normal thermal movement and house settlement
• Shrinkage cracks from new plaster drying
• Structural movement (requires assessment)
• Impact damage
• Damp causing plaster to blow

Step-by-step fix

1. 1
   Identify the type of crack

   Hairline cracks (under 0.5mm) are cosmetic. Cracks wider than 5mm, diagonal cracks running from window or door corners, or cracks that are growing warrant a structural survey.

2. 2
   Open up the crack

   Use a scraper or filling knife to open the crack slightly into a "V" shape. This gives filler something to grip.

3. 3
   Dampen the area

   Mist the crack with water before filling. Dry plaster absorbs moisture from the filler too quickly and can cause it to crack again.

4. 4
   Apply filler

   Use a flexible ready-mixed filler (Polycell or Ronseal options work well). Press it firmly into the crack and smooth off with a damp filling knife.

5. 5
   Sand when dry

   Allow to dry fully (2-4 hours for most fillers). Sand smooth with fine sandpaper.

6. 6
   Seal before painting

   Apply a dilute coat of PVA adhesive to the filled area before painting. This prevents the new paint from drying differently to the surrounding wall.

Frequently asked questions

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