Making Sense of Deck Finishes
Q: What should I do about conflicting advice I’m getting about deck finishing? I just built a new staircase out of cedar for my deck and the measured moisture content of the wood is less than 10%. Some brands of deck stain recommend letting new wood weather 4 to 12 months, then use a cleaner and brightener before applying a finish. Other brands say it’s okay to sand and apply stain whenever the wood is below 17% moisture content. One brand of stain says to stain all six sides of each board while building, which I can’t do now. Have I messed up?
A: No, you haven’t messed up. Not at all. One reason for the conflicting advice about deck finishing is that manufactures can’t always trust people to know the actual moisture content of the wood of their new decks. Some companies are more cautious about this than others. Waiting for a year, then prepping the deck and finishing it, is a foolproof way to ensure people don’t apply deck stain to wood that has a lot of internal moisture. In your case, if you’ve measured the moisture content in the middle of a freshly cut face on the end of a board with a meter and found it to be drier than 15%, you’re A-okay for finishing. This is true even if you’re using the most moisture-averse finishing products. Like I said, the safest approach is to cut a piece of the lumber you used for building, then test the middle of the cut face for moisture content. Wood can be superficially dry, but internal moisture will eventually get out, causing deck finish failure. If a board is dry enough within, then it’s dry enough indeed. Moisture meters are cheap and effective these days. That’s my meter in the photo below. I use it all the time.
Finishing All Six Sides?
As for finishing on six sides, I’ve never found it to be crucial. Some finish manufacturers recommend this, but in my experience you don’t get significantly longer finish life on the surface of the boards with all sides finished. Even if you did, that benefit wouldn’t last long because you can never strip and refinish all six sides of each board once a deck is built anyway. Sooner or later (perhaps in only two or three years) you’ll only able to strip and refinish the top of each board anyway, and maybe an exposed end or edge. That’s what’ll happen surprisingly quickly when it comes time to strip your stairs and refinish them.
Make Any Deck Better
The main factors for creating a deck finish that lasts as long as possible is proper surface preparation, that and applying a deck finish that actually has the ability to last for a while. Many deck finishes are doomed to a short life no matter how well you prep the surface. They’re just not very good so you need to go with something that has a proven track record. Are you building a new deck? Perhaps replacing the top boards on a deck frame that’s otherwise good underneath? For deck finishing advice that I know works, and for ways to make any deck design last longer and look better, check out my online course HOW TO BUILD A DECK. Use the coupon code BONUS20 to save $20 off enrolment. The video below shows some of the unique details I explain in the course, details that can be applied to any deck design to make it last longer and look better. Sikkens DEK is my go-to product when I want a furniture-grade finish on a deck. Cabot Decking Stain has been the best deck finish for long-term use, ideally if you can find the oil-based version.
Deck Building & Finishing Course
Deck Design Detail Video
Check out this video on deck details. I made it back in 2010, but it still applies 100% today.
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