Use a plastic spreader or popsicle stick to mimic the sill’s original slope (the slight downward angle that sheds water).
A rotted window sill can be a frustrating and potentially costly problem for homeowners. Not only can it compromise the structural integrity of your window, but it can also allow water to seep in and cause further damage. Fortunately, fixing a rotted window sill is a relatively straightforward DIY project that can be completed with the right tools and materials. fixing rotted window sill