New England winters are hard on exterior wood. I’ve refinished enough decks, trim, and siding over the years to have strong opinions about how to do it right. Most of what I’ve seen go wrong came down to one of four things.
Clean it first. Everything else is pointless if you skip this. A pressure washer at low-to-medium pressure works well for decks and rough siding. For trim, a scrub brush and TSP substitute solution is usually sufficient. You’re trying to remove dirt, mildew, and the grey oxidized layer that forms on weathered wood. If you paint or seal over that layer, you’re sealing in a failure that will show itself in two years.
Let it dry completely. Wood needs to be genuinely dry before you apply any finish — not surface-dry, but dry through. In Vermont in the summer, that can mean waiting three or four days after cleaning. If you have a moisture meter, use it. For a deck, I want to see below fifteen percent moisture content before I put anything on it. Most people don’t wait long enough. Most failures I’ve seen trace back to this.
Sand between coats. Not aggressive sanding — just enough to knock down raised grain and give the next coat something to grip. Eighty grit for rough wood, one-twenty for smoother surfaces. This step gets skipped constantly. It matters more than most people think.
Watch the temperature window. This is the Vermont-specific issue. Most exterior finishes have minimum application temperatures — usually around fifty degrees Fahrenheit — and that includes overnight temperatures, not just the temperature when you’re applying. Apply a finish when it’s going to drop to forty that night and you’ll get a poor cure. September is the right time for this work in New England. October is pushing it. If you’re thinking about it in November, wait until spring.
On product choice: I’ve used most of the name brands over the years. They’re not all equal, but the difference between a good product applied correctly and a mediocre product applied correctly is smaller than the difference between any product applied correctly and any product applied badly. Do the prep right. The finish is secondary.
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