Peeling Window Sills and Frames
 

Description:
Loss of adhesion of the paint film (usually down to the bare surface) around window frames and sills.

Possible Cause:
Paint usually peels from window sills and frames because of condensation. Water standing on the sills eventually penetrates the paint film. When it later evaporates, the pressure from under the film causes peeling.

Paint also peels from window sills due to poorly sealed framing that was not properly caulked or the caulk has cracked or peeled away.

Solution:
Remove all the paint by scraping and, if necessary, using a chemical stripper. The use of a heat gun is a good alternative to chemical strippers. Either method can damage unprotected glass or window-sealing materials. Follow all manufacturer directions when using these products. Caulk where necessary especially at every 90° angle and crevice to eliminate any opportunity for moisture to penetrate into the wood substrate. Coat the sill with an exterior primer and finish coat. When painting frames, leave a small 1/16 inch edge of paint on the pane to prevent water from getting behind the film. Open vent holes in aluminum window trim.

Other solutions involve using cedar wood as a replacement for pine, which soaks up water like a sponge. Paint the butt ends of the wood before replacing the sills.

The use of storm windows and dehumidifiers helps prevent recurrence of peeling.

Recommended System:
Primer
1 Coat of FLEX BON #169 Series Exterior Alkyd Primer
Topcoat
2 Coats of Top Quality FLEX BON Exterior Latex Paint