How to Choose a Finish for an Outdoor Project

How to Choose a Finish for an Outdoor Project

If you’re planning on adding some furniture to your porch or outdoors, Chris Marshall explains your options and shows what he used on his mahogany porch swing project.

Chris Marshall: Hi folks, I’m Chris Marshall, with Woodworker’s Journal Magazine. Woodworking is all about making decisions and answering questions. And when it comes to the finishing stage of a project, the decisions and questions just continue. For every project, I ask myself things like these:

  • What do I want the finished look of the wood to be?
  • How durable does the finish need to be?
  • Is it compatible with the wood I’m using, or with stain I’m planning to use?
  • And, can I apply the finish successfully with the skills I have?

CM: Well, when I was choosing a finish for this mahogany porch swing project, I had to ask myself these kinds of questions to land on the best exterior finish for the job. And, I knew I wanted to use a commonly available, home center option. If you haven’t finished many outdoor projects, I thought it might be helpful to share some of those home center options for exterior finishes, and my thoughts about choosing one of them for this particular project.

CM: Let’s take a look at the typical home center exterior wood finishes. Here, I’ve got a scrap piece of the same mahogany I used for the swing with these finish options applied to it, so you can see what the result looks like. First off, there’s good old paint. It’s easy to apply, it’s very durable and obviously, comes in every color under the rainbow. And these days, many exterior paints include primer mixed right into the paint for one-coat coverage. It’s very convenient, because one coat on bare wood, and you’re done!

CM: Now, I know there are some woodworkers who cringe at the thought of painting a hand-made woodworking project, but sometimes paint is the right choice. Take this Adirondack chair, for instance. I built it about a year ago for our magazine. It’s made of cypress, and the color of the wood was all over the map, so I was fine with hiding it. And, Adirondack chairs are often painted in fun, bright colors, so paint was totally appropriate here. It’s wearing really well. Even after a year in the full sun, it looks just about as good as the day it left the shop. But for this mahogany, which has a grain pattern that’s way too pretty to hide, painting it would have been a shame. So, paint wasn’t an option.

CM: Next down the line, I could have chosen one of these two mostly clear home-center finishes, which are actually very different. This one is a wood and deck sealer, and this one is spar varnish. Deck sealers are a combination of chemicals and oils with UV inhibitors and mildewcides blended in. Clear versions don’t color the wood very much, but they do help to keep it from turning gray too quickly and they’re easy to apply by just flooding it on and letting it dry. But if you’ve got a deck, you know that you have to keep up with deck sealers because the finish doesn’t last very long. For a project in full sun, you might only get a couple of seasons before the wood starts to look dry again. I wanted something longer-lasting.

CM: Spar varnish, this other clear finish, is another option you may have seen at the home center. Spar varnish can be a great choice for exterior projects. Boat-builders have relied on it for many decades. It seals wood inside a film coating to keep water out and to help block UV rays. And it’s formulated to be more flexible than other varnishes so it can expand and contract with the wood as the humidity and temperature changes. That’s really important for any exterior wood finish: it has to move with the wood. But even though spar varnish is durable and easy to apply, I didn’t want a shiny, coated interior looking surface for this project. I wanted the wood to look as natural as possible.

CM: So that led me to the exterior stains aisle at my home center, and I think exterior wood stains have a lot of upsides. They come in lots of attractive wood-tone colors. They’re easy to apply: just flood it on, let it soak in and wipe off the excess. Exterior stains have UV inhibitors to keep the wood from turning gray. And, they soak into the wood fibers to offer reasonably long projection — especially if a project is in partial to full shade, like on a covered porch. They’re a nice “close to the wood” finish.

CM: With exterior stains, you have to make some choices. First, how much do you want to hide the wood grain? There are solid-color stains like this, which totally hide the wood’s natural grain. They actually perform more like a thinned paint than a typical stain. And, if a solid-color stain fails, I’ve found that it can peel just like paint. Then, there are transparent stains, like this. They color the wood but without hiding the wood grain. They’re also thinner than solid-color stains, so they soak in better and won’t peel off.

CM: BINGO! For this mahogany porch swing, I chose a semi-transparent exterior wood stain. I also went with an oil-based formulation instead of a water-based stain. And here’s why I did that: with all the slats, nooks and crannies on this project, I didn’t want the stain to dry too quickly and end up looking blotchy and inconsistent. That can happen with water-based stains. Oil-based varnishes dry much more slowly so you can flood it on to the entire project, let it soak in and wipe off the excess for a more consistent look. And when the time comes for me to refinish this swing — and it will! — all I need to do to refinish it will be to clean the wood apply more stain. Simple.

CM: Now, an oil-based exterior stain might not be the best choice for your outdoor project. Maybe you want a more vibrant color, no color at all, or you just love the look of shiny, varnished wood. Hey, it’s all good! But, I think it’s important to know what your outdoor finish options are, along with their strengths and weaknesses. Then, choose the one that suits YOUR tastes and project best. I hope this video has helped you see my thought process for this project, so it’s useful when you’re choosing an outdoor finish, too. Thanks for watching!

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  • Ed Judge

    These were all ‘Home Center’ choices. What would your choice be for non-Home Center options?

  • keithm

    Spar Urethane? It’s been my experience this has low UV resistance and will crack and peel in short order. This would create a refinishing nightmare. Do you have success with this?