Preparing walls before exterior repainting
Masonry paint bonds to what is underneath it. If that is a live layer of algae or a dusty, chalking surface, the new coating fails from below no matter how good the paint is.
Ask us about this
Monday to Saturday, 8am – 7pm
- Use a biocidal wash, not just a rinse
- Allow several dry days before painting
- Inspect for cracks once the wall is clean
What has to come off first
Surface growth, loose and chalking material, and any organic film in the texture. A biocidal wash kills what is growing rather than just wetting it, which matters because spores left in place carry on working under a fresh coat.
Drying time before the first coat
Masonry holds water well after washing. Painting too soon traps moisture behind the film and causes blistering. In South West conditions, allowing several dry days after cleaning is more realistic than the minimum figures on a tin.
Where cleaning reveals repairs
Cleaning frequently uncovers hairline cracking or previous patch repairs that were hidden under growth. Better to find those before paint goes on than to paint over them and see them within a year.
Common questions
- Do you paint as well?
- No, we prepare the surface. Decorators generally prefer to take on a wall that has already been properly cleaned.
- How long after cleaning can painting start?
- It depends on the weather and the substrate. We will say what we think based on the wall on the day.
- Is cleaning still needed if the wall looks clean?
- Usually yes, because chalking and airborne film are not visible until you wipe a hand across it.
Similar situations
Tell us your painting date and we will schedule the wash far enough ahead of it.
Get a written quote