I have a staircase which is under direct sun light (through glass window). After 20 years, the top coat is gone. Usually, when finishing wood, one would applied a coat of sealer to seal pores on the surface of wood. Would this sealer coat also be decomposed by sun light?
Find one rated for outdoor use, eg spar urethane. Is the coating gone all over, or just where it's worn down from traffic? I'm assuming the former, otherwise it's not UV related.
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