If you do not remove loose paint and caulking before you paint all the work you do in painting your windows is a complete waste of time and money. Paint will bubble up on window sills and frames for a variety of reasons. There will be nothing holding it in place other than the connection to the paint. There is no connection with the wood underneath and there will likely be cracks where moisture can find its way inside causing wood rot over time. There are a variety of things that will cause the paint to chip off or bubble up. In some cases it is age and the sun that will cause the paint to deteriorate and chip away. For many people in northern climates the repeated freezing and thawing of snow and water on the window sill will also cause the paint to crack with water getting underneath and not only pushing the paint up, it will also cause the wood to rot underneath if something is not done in a reasonable amount of time.
We recommend that the windows be checked every year and if there any signs of cracking or paint peeling, the offending area should be scraped and painted. We have out lined the steps to follow below.
Caulk Before You Paint Window Frames – Steps
The first step is to scrape away all loose paint chips. In some cases this will be confined to the window sill, while in others like the picture shown it will be on the vertical surfaces as well. Next, use steel wool to remove all loose particles and roughen up the wood so that new paint will adhere to the wood. You can also use sand paper, however we find that the steel wool is more flexible and easier to get at corners and round edges. The final step before painting is to apply caulking to all joints so that there is no chance of moisture getting into areas that could cause other problems such as cracking and wood rot. Once it is dry you can then begin applying an outdoor paint.
Use Paintable Exterior Caulking
Always use exterior caulking that is flexible, will withstand extremes of temperature and can be painted. After all you do not want to have caulking that cannot be painted marring your window frames! Where ever there is bare wood, you probably should apply a primer paint first and then apply whatever color you chose. We have always just apply two coats of the regular paint with good results since the wood is already sealed from the initial coat of primer paint.
Follow these steps every year and your windows should last many years. If someone is painting the windows for you, always discuss the details in terms of scraping and removing loose paint, caulking and painting as discussed above.