You just bought some decking or flooring (or really any lumber) and one of the first things you hear is that it needs time to acclimate to its new surroundings before you do anything with it. The maddening thing is you will rarely get the same answer twice when it comes to how long that particular lumber should sit around getting in touch with its feelings. If pressed for an answer to “how long should my decking acclimate?” I can answer with a solid “it depends”. Trying to apply a universal answer to a problem with so many variables is what gets people in trouble. You have to look closer and apply our understanding of wood science that we have been building by reading this blog.
There are 4 questions you should ask yourself in order to answer this question:
1. How Will It Be Installed?
Is your deck face screwed or using a clip system. Screwing it down means your boards are going to move a lot less because they are physically restrained. Clips, not so much. There is a screw running through the clip and into the lower tongue of the grooved edge but this is just no substitute for a screw or 2 driven through the entire board and restraining the board from cupping. So if you are face screwing then you can pretty much get right to work and assuming you follow proper gap spacing your boards will behave. With clips its better to stack and cover the lumber near the deck site and let it sit for 1-2 weeks so that most of the movement that will occur does so before the boards are laid down.
2. What Time of Year Is It?
Wood moves year around but in the winter months it is pretty stable. The sun may heat up a decking board in the afternoon but with ambient temperatures low there is much effect. Plus the cooler it is the less moisture is in the air so the wood is shrunken. With very little moisture in the air and the wood to begin with moving it from the lumber yard to the job site won’t see a great deal of change in the conditions. You can start working almost immediately after receiving the decking. Maybe let it sit for a day on the job site, stacked and covered before starting to install it. Again, following the rules of gap spacing is essential because the boards you install now will swell up quite a bit in the summer months.
3. Is It Pre-Finished?
Did you buy the decking already finished or will you be applying the finish before installing? One of the biggest misnomers of the wood finish world is “sealer” or “sealant”. Finish does not seal the wood and prevent it from moving. It will slow down the movement of moisture in and out of a board (which causes the movement) but never can you stop it. Moreover a finish will add moisture to a board so you need to consider how long ago the board was finished and give that injection of moisture some time to equalize. Then you also need to account for all of the other factors listed here and probably wait even more time for those factors to equalize. Once the boards are in equilibrium the finish will help to keep them very stable as the spikes in moisture and temperature that happen during the day and converse at night will even out.
4. Where Will it Be Installed
How far did the decking travel from your supplier to the job site? What are the conditions at the job site? Ideally a deck should have plenty of ventilation underneath but that isn’t always possible. How much sun will the deck see on an average day? All of these factors will force a significant change in the moisture content of the decking and the boards will need to move around a bit and get that change out of their system before you start screwing them down and forcing them to lay flat and still. A week on the job site stacked and covered and even possibly leaving the shipping banding in place to restrain the boards while they settle would be the minimum wait period.
When In Doubt, Wait a Bit More
There are even more factors to be considered in more unusual circumstances where perhaps there isn’t enough ventilation under the deck or it is being installed in a really harsh environment like a rooftop with direct sun all day long. When in doubt, let the lumber sit even longer. Keep it stacked and covered just as long as you can and try to give it a full 2 weeks to equalize with the job site conditions.
There really is no exact science to all of this as I’ve seen decks come right off the truck and get screwed down all in the same afternoon with no ill effects. I’ve seen decking actually glued directly to a concrete slab with no problems. And I’ve definitely seen the converse where decking in those same conditions buckled and cracked and did all kinds of unspeakable things. But I have not seen a deck when given proper time to acclimated with all of the above taken into consideration do anything but behave nicely.
That’s Decking, What About???
Ready for the fun part? We are just talking about decking right now and flooring or siding or manufacturing parts for furniture or something else is an entirely different ball of wax. When you have any kind of interlocking joinery it can be risky to let the boards sit around for weeks or even days. You see the joinery is milled to precise specifications and if the wood swells those joints may not fit easily any longer. Again this is a question of variables and which ones you can control. But this is a topic for another post. For now recognize that we are only talking about decking here where the boards are not joined and a gap is left between them With other things like tongue and groove porch floor or rainscreen siding, some of the questions may be the same but the answers could point in a different direction. That’s a topic for another article. Isn’t wood fun?!