TECH TIP: Two Ways to Finish Outdoor Wood

Finishing wooden decks, fences, outdoor furniture, picnic tables and gazebos is not as simple as it looks, and too many people pay a high price for this illusion. The hidden danger doesn’t come from product application, but starts sooner than that with product choice. Choose wisely and maintenance of your outdoor wood will involve little more than a simple cleaning and re-application of finish every few years. Choose poorly and you’ll face the nightmare job of removing the remains of an ugly, stubborn old peeling finish that requires enough scraping and sanding work to make you scream. 

How Will Your Wood Stain Age?

The main thing to understand is the difference between film-forming outdoor finishes and those that form no surface film. Paints, varnishes and urethanes are all designed to form a protective film that seals and colours wood. This is fine as far as it goes, but not when the outdoor item you’ve painted has lots of nooks, crannies, corners and gaps between boards. As film-forming finishes fail, they need to be completely removed by chemicals, scraping and sanding away what’s left. This can either be easy or a huge pain, depending on the design of your wooden item. It’s not unusual to have to spend 4x or 5x more time stripping an old film-forming finish than the time it takes to apply a new one. And who has that kind of time to waste? 

Film-Free Finishing Oil

Outdoor finishing oils are the classic no-film option for outdoor wood. These UV-protective oils get sloshed on by brush or sprayed onto larger areas and are forgiving in lots of ways. Since they soak entirely into wood, there’s no chance of runs and hardened drips forming on the surface. And since outdoor oils form no film, there’s no chance for a nightmare prep job later on, when it comes time to recoat the wood again. Just clean the surface with a hose brush or pressure washer, let it dry, then coat again with more oil.

I’ve been monitoring outdoor finishing products since the early 1990s, and my current favourite outdoor finishing oil is Minwax Teak Oil. It’s listed for use on dense woods like teak, mahogany and rosewood, but I find it works just as well on softwoods like cedar, pine and pressure-treated lumber that’s weathered for a while. Oil like this is a bit too light duty for use on decks, but I do recommend it for all other outdoor wood applications where a natural, amber oil look is what you want. Outdoor oils require annual reapplication, but the work is fast and easy, so it’s simpler than it sounds. 

A New Low-Film Wood Stain

The only drawback with outdoor finishing oils is that they don’t impart much colour to the wood. And when you’ve got grey wood to beautify, or you simply want more colour than your current wood provides, something more than oil is required.

Thompson’s Water Seal has a new stain program this year, and it’s promising enough that I’ve added it to my roster of ongoing outdoor wood finishing durability samples. It’s based on a soak-in water repellent just like the legendary Thompson’s Water Seal, but it’s combined with a solid, or semi-solid colour  – five shades in each category. 

Although this product hasn’t been around long enough for my test samples to say much about durability, Thompson’s Water Seal Stain does come with a published life expectancy of 4 to 5 years for decks, and 6 to 15 years for fences, depending on whether you choose semi-transparent or solid colours. Thompson’s also offers a refund policy if you’re not satisfied at any time during the life expectancy period. And though this policy doesn’t cover the labor costs of preparing the surface and reapplication, Water Seal Stain forms almost no surface film. This means that prep work should be quite easy when it comes time to renew the finish or change it.

There are many ways to go wrong finishing outdoor wood, but now that you know the basics, it can save you from a lot more grief than immediately meets the eye. After all, enjoyment is the reason we have outdoor wood in the first place, so the less work the better. 

Posted on June 3rd, 2014

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