Concrete surfaces for painting
There are a number of problems relating to preparing or producing a concrete surface suitable for painting. This is a particularly difficult problem when the end result is required to look like a painted plaster. Many specifications seem to call for a made-good concrete finish’. After the concrete has been painted the results are often disappointing. Small blow-holes that are unobtrusive before painting can become very apparent, particularly if a thin, light paint is used. The thicker and darker the paint the greater the chance that the holes will be covered. Attempts to fill in or grind off slight steps on the surface of the concrete may become more obvious when painted, because of the different texture of the surface.
Guidance on achieving a good surface for painting may be found in Concrete Advice No. 14, Concrete surfaces for painting.