House Paint Problems - # 4, Chalking

Symptoms: Chalking


Chalking is identifiable as a fine chalky powder that forms on the surface of a paint film. Although some chalking is a normal way paints self clean when exposed to the sun and rain, excessive chalking can be a paint failure. In dry arid climates where there is little rain, chalking can become excessive. Chalking is actually the paint pigment released by the paint binders which have been broken down by exposure to the weather. Chalking is especially typical of very light colored flat paints, especially lesser quality oil based paints containing high levels of pigment extenders. When chalking gets severe it may run off onto and stain surrounding construction as in the above photo.

Potential Causes:

•Use of cheaper quality exterior paint containing high levels of pigment extenders.

•Improper paint was used in an exterior application (such as an interior paint).

•Lower quality factory finished aluminum siding.

•Over-thinning paint.

•Not properly sealing a porous surface before painting.

Possible Repairs:

•Chalking is considered dirt and must be removed before repainting.

•Remove chalking by power washing or scrubbing with a trisodium phosphate cleaning solution and rinse with clean water.

•Let dry and paint with a high quality latex house paint.

•To clean brick areas stained by chalking runoff the masonry should be scrubbed with a specialized masonry cleaning solution. If staining persists, a professional cleaning contractor may be required to clean the brick.