We get a call once and a while on the exterior of a home looking chalky, pasty, or white streak marks down the siding. What is it, what is it from and how to fix it are great questions that I called out Sherwin Williams Representative Jason Leonard

David: Ok Jason, what is chaulking in a house?
Jason: Chaulking by definition is the Formation of fine powder on the surface of the paint film during weathering. It can cause color fading. Some degree of chalking is a normal, desirable way for a paint film to wear, but excessive film erosion can result in heavy chalking.

David: What will cause it?
Jason: there are several reasons and or causes
• the previous use of a low-grade, highly pigmented paint.
• Using an oil-based paint. (These tend to chalk more than latex formulations).
• Aluminum siding can develop an excessively thick chalk layer and will require power washing to ensure complete chalk removal.
• Use of an interior paint for an outdoor application.

David: So what is a good solution to get rid of it?
Jason: Remove chalk by washing siding with detergent and water or by having it professional power washed. If some chalk remains after first washing, then wash again for complete removal. Rinse well with clear water. Allow to dry thoroughly. For the best resistance to chalking, use a higher sheen such as satin or gloss. Brick areas that are stained by “chalk run-down” should be scrubbed with a stiff brush and detergent. Professional Cleaning may be required to remove this staining.

David: What would you use to paint over it once cleaned?
Jason: I would Recommend 2 Coats of a Premium grade Exterior Latex Paint such as our Duration paint line.

Thanks for the help Jason, if you have any questions about the full line of Sherwin Williams exterior stains or paints, Jason can be reached at 630-669-6523.