I have a solid wood oak door that faces due west. The sun is brutal on the finish, and I have to redo it every six months. I’ve tried sanding sealer, polyurethane, you name it. Is there anything that will help? -Van
The UV rays and heat from direct sunlight – not to mention rain, snow, and extreme changes in temperature – are very hard on exterior wood doors, especially those with clear finishes.
Your best bet is to sand the door down, and finish it with multiple coats of an exterior spar varnish that’s made for boats. Spar varnish contains ingredients that block UV rays and is more flexible than standard polyurethane, so it adheres better without cracking or peeling. Exterior polyurethane with UV blockers is also available, but it doesn’t hold up as well outside as spar varnish.
Even the best clear finish won’t provide as much protection for your door as high quality exterior paint, since the pigments in paint prevent sunlight from penetrating through to the wood.
Your best solution would be to try and keep the sunlight from reaching the door by adding a porch, awning, canopy, or strategically planted trees to provide shade.
Good luck with your project,