I'm currently laying up a stone veneer hearth for my wood stove and I'm finishing an old barn beam I saved from one of my job sites for the mantle. Id like to polyurethane the beam to make it easier to clean as its rough textured. My single wall pipe will be 20" from where it goes through the wall to the bottom side of the mantle. Do I need to worry about the polyurethane peeling or anything from the heat? It shouldn't get hot just warm, I'm just seeing if there are any paint experts on here. Thanks