What Causes Peeling Paint?

The issue of failed adhesion (aka peeling paint), seems more complicated and even overwhelming, but a paint’s failure to properly adhere is limited to essentially one of two underlying conditions: 1. Contamination on the base coat, or 2. Incompatibility of the base and top coats. Contamination Contamination includes: 

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dust left on the surface to be painted

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kitchen grease or cooking oil fumes creating a slick surface

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dirt on high traffic walls (my kids love dragging their hands along the walls when they walk down the stairs)

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dirty baseboards and stair risers, often coated in floor polish or waxy wood cleaning soaps

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mineral condensates on bathroom surfaces (steam from showers leaves evaporated salts on walls and ceilings, along with shampoo and soap surfactants)

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stain migration

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mildew growth

You can typically spot these contamination failures by looking for small breaks or fractures in the paint film, small blisters, or limited areas of paint failure (like around a door knob, but not the entire door; or only the ceiling and walls directly over a shower stall). When you’re dealing with contamination, you might see the color of the underlying wood bleeding through the topcoat. This condition also lends itself to the growth mildew and mold in high-humidity environments, like bathrooms (and the entire state of Florida…). You also may be dealing with wood tannin bleed, which is easily hidden by an acrylic stain blocking primer. This product captures and locks the water-soluble stain in the primer body and prevents it from migrating into the topcoat. Almost all interior wood trim is pre-primed these days, and most painters assume this is a viable field primer. Unfortunately, that’s not true. Wood tannin bleed is a stabilizing primer designed to help the trim resist moisture absorption while it is stored at the lumberyard, or on a jobsite. Mildew growth on paint, however, is inevitable over time. The best bathroom paint, engineered for a high-humidity environment, contains a mildewcide. But if the bathroom paint is not cleaned one or twice a year, condensates and surfactants become the food source for mildew. Since these form a layer over the paint, the mildewcide does not come into contact with the mildew, and the mildew is left to happily grow in your bathroom. Incompatibility This is a more dramatic paint failure. Incompatibility indicates a failure of the topcoat to bond with the previous coat or basecoat. You can know you’re dealing with incompatibility because that topcoat will simply be falling off. In some cases, it will be so fragile it can be easily removed with a fingernail. How does this happen? This is typically due to a topcoat being applied to a hard, glossy surface without proper sanding or priming. You most often find this type of incompatibility in older housing where old oil-based paint was in use—including clear coats like varnishes and polyurethanes.