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How to repair cracks in render

How to repair cracks in render
Hairline crazing on the surface of rendering does not need filling, but deeper cracks do, if you want to keep the wall weatherproof.


  • Filling knife 
  • Brush 
  • Wet sponge or cloth 
  • Old paintbrush 
  • Perhaps a bolster chisel and club hammer, and a ladder


  • PVA adhesive 
  • Rendering or exterior filler
1. Clean out the crack by drawing the pointed edge of a filling knife through it to form the crack into a V. The shape will anchor the filler below the surface so that the crack is unlikely to open again. You can use a bolster chisel and club hammer instead of the filling knife if you find it easier.
2. Brush out the fragments and dust from the cavity to leave it as clean as possible.
3. Wet the cavity with a sponge or cloth dipped in water. Paint the inside of the cavity with PVA adhesive to improve adhesion of the filler.
4. Press filler or rendering into the crack with the filling knife. Filler is more convenient than rendering but less economical for more than a couple of cracks. Prod the knife into the cavity to make sure there are no air pockets in it. Smooth the filling level with the wall surface. Redecorate the wall when the filler has dried.
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