Masonry Painting - Preparation

This article will discuss the correct procedure for decorating exterior masonry. This is based on experience and best practice. The article is primarily aimed at exterior house painting on cement based render, in the UK. I hope to add more articles along the same theme in the future.

As with any decorating job, preparation is the key, and on previously painted surfaces, washing down the existing paint film of any grime is a must. This can be carried out, with care, by using a pressure washer and a diluted bleach solution. Obviously, all safety precautions should be adhered to when using any chemicals and high pressure equipment. When the surface has dried out a fungicidal wash can be applied according to manufacturers instructions. This will kill any fungus spores and algae, and stop the fungus and algae from living under the new paint film, and so stop the paint from peeling.

The next procedure is to remedy any defects. Large patches of soft render should be removed and re-rendered. small patches of missing and damaged render can be repaired using a suitable exterior masonry repair filler. A good tip here is to use a damp sponge to smooth the filler into the existing render, just before the filler hardens completely. Hairline cracks can be filled with a suitable exterior flexible caulk. Larger cracks should be cut out with a grinder in a V shape, and filled with a suitable exterior filler. Although if the surface is to have a lime wash finish then care should be taken with the type of filler - a breathable filler needs to be used.

All flaking and blistered paint should be removed, and any chalky or friable surfaces should be coated with a stabiliser solution to bind the surface ready for painting. Again, some stabilizer solutions should not be used on lime render.

Any bare unpainted render can be primed with a masonry sealer prior to painting. But care should be taken in using the appropriate sealer. Water sealers for example are mostly silicone based, and cannot be overpainted.

On using the correct materials for the job, then you're nearest supplier should be able to advise you, failing that contact the paint manufacturers direct.

If all this seems to much then click on the following link, if you need more advise or the services of a painter decorator.

If you are looking for ideas and help on choosing the right colour for painting your property, then I hope to cover that in a future article, but for now click on the following link for a brief article on painting external masonry.