I constructed an outdoor bench of cedar 2 x 4s and finished it with a semi-gloss spar varnish over the bare, non-stained wood (four coats, applied as directed). After one year in the elements, the finish looked terrible, with black marks that extended through the finish and into the wood. I sanded the wooden pieces down to bare wood, removing all the black marks, and reapplied the finish only to have the same thing happen again in less than a year’s time. What do you suggest for a more weather-proof finish that will hold up? – Dan Peterson
Chris Marshall: Dan, spar varnish is your best bet. It’s formulated to be more flexible and UV resistant than other film finishes, to better suit outdoor applications. But, as our finishing expert Michael Dresdner has said before, eventually the sun and the elements are going to win this battle. I choose not to fight it in the first place … I like the look of weathered cedar, left unfinished. It turns that silvery gray which, to me, looks graceful and fitting for outdoor projects. And, I’m never left with the tedious job of sanding and re-coating. I like preserving the original color and look of other woods for indoor projects, but cedar is going to be gray in my project color palette.
Tim Inman: What weatherproof finish will hold up outdoors? Two-part epoxy swimming pool paint. Just kidding – sorta. Your dilemma is an often heard one. Truth is, there is not a good solution for it. Ultraviolet light, water and sudden temperature changes to the extremes make finishes fail. Outdoor finishes fail faster. Paints, which are colored and made opaque with pigments, stop the UV light at their top surface. That is why many paints get “chalky” after exposure to the elements. They hold up longer because the pigments stop the UV from burning on down through the finish layers, destroying them from within. Such is not an option for clear films like varnishes, etc. They will fail all the way through all at the same time – and quickly in most cases.
You have two choices. 1. Keep fighting Mother Nature by reapplying the coating often, tolerating the frustration in order to retain the look you want. 2. Learn to live with what Mother Nature has made. Cedar is a non-rotting wood that will last for decades, if not centuries, outdoors. It does not need any ‘protection’ with things like varnish, thank you. It will develop what some people (me) consider a beautiful silver-gray color. I have some cedar fence posts on my farm in Iowa that my great-grandfather put into the ground before World War I. They are still as good as the day he set them. I’d go with the natural weathered wood look, and learn to enjoy it. Otherwise, you’ll be fighting a losing battle from the start.