How to Fix Peeling Window Sill Paint

What is Cracked Window Sill Paint?

Paint film around window frames and sills can lose its adhesion, usually exposing down to the bare surface.

Paint usually peels from window sills and frames because of moisture. Water standing on the sills eventually penetrates the paint film. When it later evaporates, the pressure from under the film causes peeling. This moisture may be condensation on the interior, or rain and snow on the exterior.
Paint also peels from window sills due to poorly sealed framing that was not properly caulked, or the caulk has cracked or peeled away, allowing water to undermine the coating.

Remove as much paint as possible by scraping or sanding, or using a chemical stripper, or heat gun. Follow all manufacturers' directions. Test the coating in a six to 12 inch radius around any peeled areas to be sure the adhesion is adequate.
Prime bare surfaces with the appropriate primer and caulk where necessary to eliminate opportunities for moisture to penetrate into the painted surface. Be extra thorough around angles and crevices.
Do not seal or paint shut any vent holes in the window trim of storm windows.
If a wood surface is deteriorated, replace it using cedar, redwood, or pressure-treated wood. Prime the butt ends of the wood before installation to reduce moisture penetration.
The use of storm windows and dehumidifiers may help prevent recurrence of peeling.
We do not recommend painting over cracked window trim for two reasons. The cracking may persist and your finished paint job will have an unattractive texture.

One you have removed as much paint as possible create a strong seal with White Lightning^® Silicone Ultra Window & Door Sealant. Before painting you may need to prime. We recommend Multi-Purpose Interior Oil-Based Primer. Then finish the job with ProClassic^® Waterborne Interior Acrylic Enamel.

Removed peeling paint then reinforce any seals with White Lightning^® Silicone Ultra Window & Door Sealant. If you need to prime, use Multi-Purpose Latex Primer and finish with SuperPaint^® Exterior Acrylic Latex to protect against the elements.