Things You'll Need
Fine-grit sanding block
Bay windows typically have two common problems that can cause damage. The first is a faulty seal between either the glass and the frame or the frame of the window and the wood trim. This can cause leaks that lead to water damage on the surrounding wood. This brings up the second most common issue with bay windows -- damaged window sills. You can repair both of these problems without the help of a professional. However, if the bay window is cracked or broken, call in a professional glazier to do a replacement.
Sealing a Leaky Window
Apply masking tape on both sides of the original caulking, leaving a 1/4-inch width between them.
Lay down a 1/4-inch bead of caulk between the tape. Depress the caulking gun trigger to release the caulk.
Smooth out the caulk with the bottom of a spoon. This gives the caulk a finished appearance.
Remove the masking tape immediately. Do not let the tape sit or the caulk will cure on it and you will not be able to remove it.
Repairing a Damaged Bay Window Sill
Assess the damage to the sill. If the water damage extends more than 1/4 inch into the wood, you will need to replace the entire sill. If not, you can repair this on your own.
Sand down the window sill with a hand sander. Do not start the sander when it is in contact with the wood or it will gouge the surface. Hold it up, turn it on low and lower it slowly on to the wood. Sand the entire sill until the damaged area has been removed.
Sand the surface again with a fine-grit sanding block. This will prepare the wood for refinishing.
Stain or paint and prime the wood. If staining the wood, apply one coat of stain and let it dry for four hours. If the desired color has been reached, proceed to the finishing stage. If not, apply another coat and let it dry. If painting the wood, prime the surface first and let the primer dry. Apply at least one coat of paint to the wood.
Seal the wood with a clear polyurethane sealer. This will help prevent future water damage. Paint on one coat of sealant and let it dry.