Q&A - Dirty exterior walls

QUESTION
I have attached two photo’s of theexterior walls of our apartment blocks. The Blocks were completed about 6 years ago and as you can see are getting a little dirty. Most of this is caused by the coping stones not overhanging the wall sufficiently. We had the walls steamed cleaned last year but this was not terribly satisfactory. Is there a material that can be applied to the walls, so the dirt just runs off ? Or do we need to seal the concrete coping stones?

Terry Willgrass

ANSWER
The problem you have described is a common one, and affects many exterior finishes, even when they are supposed to be self cleaning! The best and most permanent solution is to provide suitably sized coping stones, so the water doesn’t run off  the drip edges directly onto the wall finishes beneath and stain them. However a coating may help alleviate some of the appearance of the staining, although it would not be a complete solution. You could try a good quality clear elastomeric (breathable) coating such as Belzona 5231 (SG Laminate) on a test area and see if that helped. But do not be fobbed off  by some of the low quality coatings available in some DIY stores.