Putting a clear finish on wood that's exposed to the sun commits you to a lifetime of maintenance, or at least until you get tired and go back to painting it. UV radiation inexorably breaks down the finish, and degrades the wood fibers, which weakens the bond of the finish so it crumbles or flakes off. Two years is all you can expect from traditional varnish, even if the sun is on it only half a day. There may be better products, but I can't imagine they'll extend the maintenance intervals by very much. There's only so much UV inhibitor that can be put into a clear finish before it starts to look cloudy, because essentially an inhibitor is finely ground pigment.
Just be wary of applying a new and different finish over the existing varnish, in case there is a compatability problem.
Putting a clear finish on wood that's exposed to the sun commits you to a lifetime of maintenance, or at least until you get tired and go back to painting it. UV radiation inexorably breaks down the finish, and degrades the wood fibers, which weakens the bond of the finish so it crumbles or flakes off. Two years is all you can expect from traditional varnish, even if the sun is on it only half a day. There may be better products, but I can't imagine they'll extend the maintenance intervals by very much. There's only so much UV inhibitor that can be put into a clear finish before it starts to look cloudy, because essentially an inhibitor is finely ground pigment.
Just be wary of applying a new and different finish over the existing varnish, in case there is a compatability problem.
Posted by: farmboy at November 4, 2009 10:43 AM in response to Exterior Wood Finish