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Hi there, we have what I suspect to be water damage to areas of one external wall and under our door ways throughout the home. What would be the best way to repair the render prior to repainting? My husband tried to repair the render under the doorways a year ago however he never got round to painting it before it started to bubble again a couple of months later.
Hello @Pam33
Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about painting your rendered wall.
I suspect that there is a water leak happening somewhere inside your rendered wall. The reason the paint is lifting and bubbling up is due to hydrostatic pressure. Water inside the render is slowly coming out of the wall and thereby pushing the paint off the surface.
The only way to stop it is to find the source of the leak and plug it up or redirect it so that it does not travel down into the masonry wall.
It is possible to use a damp proof coating such as Dunlop 4L Damp-Proof Waterproofing. It is an acrylic brush-on membrane that will prevent rising damp, efflorescence and will resist negative hydrostatic pressure. However, water being the fluid substance that it is, will redirect itself and find the next weakest spot on your rendered wall.
The best option that I can recommend is to look for any possible leaks that might be entering your wall. Otherwise painting over the surface will result in the paint bubbling up again.
If you need further assistance, please let us know.
Eric
