Q: What should I do with 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 4-12 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. One reason for the conflicting advice is that manufactures can’t always trust people to know the actual moisture content of the wood of their new decks. 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 board with a meter and found it to be drier than 15%, you’re A-okay for finishing. 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.
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 you’ll only able to refinish the top of each board anyway, and maybe an exposed end or edge. That’s what’ll happen in 2 or 3 years when it comes time to strip your stairs and refinish them.
The main factors for creating a deck finish that lasts as long as possible is proper surface preparation, 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. Click here for a very specific online education for getting the best possible deck finish results. I made this content to help the constant stream of folks who come to me looking for help with the old and failing finish on their deck. There are lots of people out there with the same deck troubles you’re having.