Q&A OF THE WEEK: “Is There a Simple Way to Finish Outdoor Wood?”

Q: How should I seal and protect a cedar planter I just built? I’d like the wood to stay light and bright outdoors.

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A: Your project looks great in the photo you sent and your hope of keeping the cedar looking bright is a common one. The challenge keeping any outdoor wood looking new is that all finishes deteriorate over time, and stripping certain (but not all) finishes back to bare wood can be a big pain. In  your case, a planter does not have the nooks and crannies that a chair or bench would have, so stripping and refinishing is not as big a deal. But still, you’re wise to wonder about the best way to go about things because there are many ways to apply an outdoor wood finish badly. 

One excellent option I’ve used for keeping bright wood looking bright outdoors is exterior finishing oil. I know from experience that Minwax Teak Oil works well outdoors (that’s what you see above), and like all exterior oils it forms no surface film. That’s a good thing because it means you won’t ever need to invest lots of time and trouble stripping off an old film-forming finish like you would with a failing varnish or urethane. Over time oiled wood begins to look thirsty and that signifies it’s time for another application of oil. Typically an annual re-coating of oil after brushing off the dirt and cob webs is all that’s required.

On the downside, oils don’t provide as much protection as, say, an outdoor varnish. Even with regular re-application of oil, your planter will get progressively darker over the years. Is it possible to store your cedar planter indoors during the off season? This will help any finish last longer and the wood stay brighter. Even keeping the planter in a shaded location during the summer season will help it stay looking good longer. Sunlight, not moisture, is the most damaging part of outdoor exposure when it comes to wood finishes.

If you’re okay stripping, sanding and refinishing every 2 to 5 years, consider a clear coat of something called “spar varnish” or “spar urethane”. This is an outdoor-tough urethane that withstands UV deterioration reasonably well. If you want the brightest, newest appearance, spar varnish is the way to go. I’d never recommend it for a bench or chair because of the difficulty of the inevitable stripping required, but in your case it’s a reasonable option. I’ve had good results using Helmsman Spar Urethane. That’s my brushing some on in the photo below.

Another option is treating your planter with something called Ecowood Treatment. I like this stuff a lot and have been using it on my own projects for years. It makes the wood age and weather evenly. This is a less formal look than the Teak Oil, and essentially you’ll have something that looks like refined barn board after a few years. Your wood will last just as long as if it had a protective finish, but it will be less formal looking while requiring virtually no maintenance. You can see a sample board I made up for a photo below. This is not the bright look you’re hoping to achieve, but the Ecowood approach means you never have to do any reapplication/refinishing again.

You can see me applying Ecowood Treatment to some new cedar shingles I installed on an old shed. The bright, new cedar looks fabulous, but I know from experience that in a year or two uneven weathering will make the shed look bad. A consistent grey colour is much nicer and it’s quite enduring.

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