To prevent paint failure, make sure wood windows are properly flashed, prepped, and painted … and don't forget the caulk.
Some wood windows are built with sills that have no slope — or even a reverse slope — which means water can't easily drain away from the glazing. Instead, it gets absorbed by the end grain of vertical window components that sit on the sill, quickly leading to paint failure and rot.
Scraping wood windows before they are repainted removes disbonded paint and reveals areas where rot has taken hold.
After scraping, the author fills small holes and minor gouges with a quick-drying spackling compound.
Rot damage needs to be repaired. Using liquid epoxy, the author saturates and consolidates areas that have minor rot
Where damage is more extensive, he first removes as much damaged wood as possible, then rebuilds the affected area with a two-part epoxy putty.
Careful caulking helps protect exterior joints and seams from water intrusion and future paint failure. Because horizontal surfaces are especially vulnerable, the author creates a fillet with caulk to help shed water: First, he applies a generous bead of caulk, and then he smooths out the surface with his dampened finger.
To prevent water from running behind the glazing trim, the author caulks this joint around all four sides of each window, paying particular attention to the bottom rail, where water intrusion is most likely.