In Part 1, we considered how setting (ie humid or dry geographic locations) impacts decking board spacing, and in Part 2, we took a look at how species affects it. We also looked at one way in which season plays a role. Now we’ll continue in that seasonal vein by considering the way our theoretical deck previously described could instead be installed during the winter rather than the summer, only to result in disaster! Then we’ll broaden our discussion to offer some helpful tips for planning board spacing for your next deck, whenever and wherever you decide to build it.

Board Spacing by Season: Winter Installation

Let’s pretend that instead of installing the deck in the summer, you installed the same deck in the winter, with the 1-by-6 Ipe decking boards and the same ¼ inch gap between the boards. Instead of shrinking, the boards would swell along with the higher moisture levels. If each board expanded precisely the same amount on both sides, it would merely take up the original ¼ inch gap by swelling ⅛ inch on either side; however, in real life, nothing ever works out quite that neatly. Instead, as the boards absorb moisture and swell, they’ll be likely to expand beyond the ¼ inch gap. When the boards have no place to go, they will buckle and crack, and your newly installed deck will be seriously damaged. The cost of replacing the affected decking boards won’t even compare to the great frustration of your customer.

Board Spacing by Season: Overview

Let’s stick with our original example of 1-by-6 Ipe decking. If you’re installing a deck in an area and during a season of high humidity, you can do so with minimal gap between boards. As the boards shed moisture and shrink, that miniscule gap will grow to approximately ¼ inch in winter. (Note that even when you install a deck when boards are as swollen as they’ll ever be, you still want to include slight gaps between boards to allow for drainage and to eliminate having to deal with standing water.) If you were to install the same deck during the much drier winter, you’d need to plan it with a ¼-inch gap or up to 1/16-inch more than that so you can allow the boards the space they need to swell as moisture levels increase, permitting drainage as we mentioned earlier.

Proper deck installation begins with good planning. It includes sourcing high-quality tropical hardwood decking and allowing for a proper acclimation period as well as proper gaps between the boards. In order to plan for proper gaps, you’ll have to take many things into consideration: your geographical setting, lumber species, and season. As you carefully weigh all of those factors and explain to your customers how each one affects wood movement and board spacing, you’ll be able to reduce the chances of an upset customer as well as a deck that requires replacement anytime soon.