Q:
I need some advice on refinishing an overhead garage door. I built the door using plywood for the panels and clear pine for the stiles and rails. Each horizontal segment is flashed with a copper cap. I sealed the plywood and pine, then stained it and topcoated it with four coats of solvent-based spar polyurethane. Just three years later, the finish is failing on both materials. How can I achieve a better finish?
Pasquale Velleca, Cincinnati, OH
A:
It looks like you did a nice job building the door. Perhaps the finishing was incomplete, allowing moisture to penetrate. A finish that is peeling in flakes that big indicates complete detachment from the substrate. A moisture meter will tell you if the wood is wet.
One of the most critical steps to a finish like this is to seal all sides of all the parts and pieces with multiple coats. Applying only one coat of sealer is insufficient. We typically take all these parts and seal, sand, and apply at least three coats before assembly, then apply two or three coats on the assembled door.
On open edges and on ends of plywood, we use a marine epoxy to seal the wood and to prevent wicking. Because both the pine and the plywood are failing, I suspect that the door is suffering from high moisture content. If possible, consider taking the door apart partially by removing the applied pine and 1/4-in. plywood skin. Let everything dry, and refinish all the pieces again. Then assemble and add a last coat or two.
If you can’t disassemble the door, then you will need to strip or sand everything back to bare wood and refinish. I like Epifanes UV gloss as a varnish, but it is pricey. Helmsman Spar is another good choice. Another good option would be to use a semitransparent deck-stain and clear-coat system such as the Deckscapes line from Sherwin-Williams. It is not a high-gloss, high-build film finish like a varnish, and it can allow the door to breathe a bit. Sikkens has a line of superior products, but it is imperative to get to all six sides of every piece of the door. I also suggest using a good exterior weatherstrip all around the jamb if one hasn’t been installed already.
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I used Epifanes on my garage door with fantastic results after the prior homeowners let the door finish deteriorate and begin peeling. I believe that there was an article in fine woodworking or fine Homebuilding that tested how various finishes hold up to the elements throughout the US. Only the marine varnish held up. I stripped and sanded my door first, then applied a Sikkens stain, and finally the Epifanes. Unfortunately, you need to build up many coats of the Epifanes for it to fully protect. They recommended 7 coats. I never got all the way to 7 in one season. So, each year, I sand the door lightly with 300 grit sandpaper and add another coat. If I keep it up, the base layer of the varnish will never break down and I’ll never need to strip the door again.