You should always clean and prepare the surfaces properly before applying anything at all. Pressure wash, degrease, sanding, or just soap and water. If you apply paint, ANY paint, over the top of mold it will affect the underlying material and/or the paint; blistering, grain, uneven surface, etc - Just do the job properly! Even if it is impossible to cure all the mold, doing as much as you can to remove it will extend the life of the paint and underlying material. The Zinnsser paints are very good and do well in holding the stains in the film of the paint, but there is a limit to it!
Date published: 2019-01-22