When it comes to the longevity of any tropical hardwood deck that you install, one of the most significant facets of your installation is board spacing. Because of the natural characteristics of your decking boards, wood movement will greatly affect your deck. As long as you understand and plan your deck with that movement in view, you’ll be able to avoid the kind of catastrophic issues that can result from poor planning. We’ve already looked at how setting (ie humid or dry geographic locations) can impact wood movement. Now we’ll go on to take a deeper look at how species and season impact movement and need to be factored in when you’re determining board spacing.
Board Spacing by Species: Looking up the Numbers
If you only occasionally work with a new species, you can easily look up the movement percentages on our main website. If you need to look up various species on a regular basis, you may want to download this handy app. To understand the numbers, you’ll want to know a little more about wood movement; the kind that affects spacing of decking boards is referred to as “tangential,” and it’s the most significant type of wood movement that any board will experience.
In addition to species, though, you’ll also want to consider the way your boards have been cut. Because of the anisotropic characteristic of wood movement, the way a board has been cut will also impact the way any particular board moves. For instance, flatsawn boards move most significantly yet inconsistently. On the other hand, quartersawn boards move very little across the width of the boards.
Board Spacing by Season: Summer Installation
Let’s take a look at a common example. Let’s say you’re using 1-by-6 Ipe decking boards in high humidity conditions: let’s say 95 degrees with 95% humidity. The board will probably measure closer to 5 ½ inches wide and will retain that width throughout the summer months with their high temperatures and humidity levels. As autumn rolls around, though, both temperature and moisture levels begin to decrease.
Just a few months later, the temperature may be closer to 65 degrees with a humidity level close to 50%. That same Ipe decking board will probably be about 3/16 of an inch narrower. If you started out with a ¼ inch gap between boards during the summer months, that same gap would have grown closer to a ½ inch gap.
Stick with me, here, for a few more months. As the winter chill brings on the coldest weather of the year, the temperature may get down close to 25 degrees with humidity levels approximately 25%. That gap, which was once ¼ inch, is now approximately ⅝ inch. As frustrating and ridiculous as the scenario described above may be, it’s not nearly as significant as the opposite issue would be.
Continue reading with Part 3.