I have a solid wood entry door with 2 sidelights under a covered porch. Every year the exterior urethane that I use to seal the door starts to flake and fall off the door and sidelights. I built the house in 2005 and installed the door at that time. It did get rained on twice before I was able to put any finish on it. Is it possible I have trapped moisture inside the door or is this just normal for a wood door? Also is there anything I can do to stop the finish from wearing off so quickly in the future?