Want to have your UPVC painted, but can’t because it’s cracked? Don’t worry!
Repairing a crack in UPVC is perfectly possible. All you need is a suitable plastic filler (low shrinkage) and a little patience.
Small cracks in UPVC windows and doors can be repaired with little to no trace. Larger cracks can cause structural weakness, which represents a significant security risk. For this reason, the advice in this guide covers small cracks (up to 5” in length) that have not split the UPVC or sheared it away.
Step 1: Clean the crack and surface
The surface around the crack and the crack itself should be cleaned thoroughly with a fragrance-free soap and rinsed. Finally, use methylated spirits to wipe down the surface and rid it of any exterior contaminants.
Step 2: Apply compound
We’ll keep this really simple – Weiss Cosmofen RM SP-710.110 is a brilliant compound for repairing UPVC. It’s about £15 on Amazon and is good for repairing cracks, chips, dents, low quality or false drillings and other damage.
It comes in two parts: a powder and a liquid. The compound is created by mixing the two together, like a resin. After mixing, the compound must be applied within two minutes or else it will become too hard to work with. After 25 minutes, it will be hard enough to sand down and blend into the UPVC.
Apply the compound to the crack with a putty knife. Make sure it seeps into the crack, with a good layer of compound above it. The aim of any repair is for it to be untraceable, so once it has dried, sand it down with 240 grit sandpaper and then 600 grit.
Step 3: Final preparation for painting
Inspect the repair under both natural and artificial light. The surface should be flat and as smooth to the touch as UPVC. Give it a final wipe down with methylated spirits. Is it flat? Can you tell a repair has been made if you are standing 4ft away (other than the difference in colour between the repair compound and UPVC)?
If it looks good, it’s ready for painting. Job done!
