Fixing Rotting Wood Windowsills

If you have an issue with a spot of rot on a windowsill, take care of it immediately to avoid further damage. Wood rots when moisture gets trapped in the wood. One way to avoid this is to provide quality finishes for any wood windowsills to protect it from moisture.

Since no finish is completely impenetrable, some painters will leave a small portion of a wood windowsill unpainted to allow moisture to escape, usually an unobtrusive bottom portion.

Wood that has a small soft spot or a sill that has little loss in the way of wood can be repaired. There's a product called Stop Rot that works well for this task. It hardens and molds to soft wood to prevent further softening of the wood.

Some hardware stores sell wood repair kits that offer a wood hardener, such as Stop Rot, along with a wood filler and basic tools in a handy little kit. For one small repair, this may be the best solution.

In lieu of the handy, dandy kit, use the Stop Rot or a similar wood hardener. Make sure the area is clean and dry and wear gloves. Use a disposable paint brush to apply the hardener. Let it dry according to the instructions.

Using a wood filler, fill the area just above the surface. Some wood filler has a spackle consistency, other may be a more sturdy epoxy. Again use gloves to apply, particularly with epoxy which is known to cause problems if it gets on your skin. Allow to dry according to instructions then sand smooth.

Paint over the area and check surrounding areas occasionally to make sure other areas are not having an issue. Unfortunately, with wood rot on a windowsill, there's often an underlying problem that may need to be addressed, so try to determine the cause rather than just making the repair.