The idea of 2×10 boards for the deck surface actually seems like a pretty decent one, especially if you have ideas towards a very large deck, covering a good deal of area. But is it a feasible idea and one that you could easily employ without significant drawbacks?
Despite how good it may seem in your mind or even on paper, constructing your deck with 2x10s for the deck boards is not going to work out for the best. The problem is with shrinkage and expansion and because most of that occurs across the width of the board, it can look quite bad.
Deck boards already have problems when it comes to shrinking and expanding, not to mention the fact that they will almost naturally warp given enough time and seasonal changes. Adding all of that extra width to the board is just asking for it.
You can control the size changes that wood undergoes over time, at least to a degree. However, when your width is 10”, nearly a foot across, controlling those changes becomes highly difficult, nigh on impossible to do.
Why Would 2×10 Deck Boards Warp So Much?
The reason that any wood will warp is that over time, changes in the air humidity, temperature, seasonal rain, and more physically affect the wood. Wood is porous, after all, and moisture makes its way down, into the fibers of the wood, where it swells up, expanding the boards.
When that moisture dissipates, the boards shrink back down. This is especially true during the driest winter months when the air carries less moisture. If you live in a predominately arid environment, treated wood will lose its moisture within a few days of installation, shrinking the wood.
All of the shrinking and expansion that deck boards go through causes another, far more irritating side-effect, which is warping. This is the biggest reason against using a wide board such as a 2×10.
When a really wide board warps, it often curls inward to a degree. This curves the edges up, creating vicious little toe jammers and disrupting the smooth, flush look that a deck only truly has when it is first constructed. This curling effect also creates another problem, which is cupping.
Cupping is exactly what it sounds like, when the deck boards bow inward, creating a cup. These unfortunate cups in the deck boards hold rainwater, rather than allowing it to drain in the gaps between the boards.
Not only is rainwater slick and unsafe for those walking across it, but it’s also no good for the deck, as the water will do damage over time, even if you stained it well or painted the deck after you put it together.
What Lumber Sizes are Best for Deck Boards?
The deck boards and railings are going to be the most visible part of the deck and also the part that is most interacted with. They need to be durable, long-lasting, aesthetically pleasing, and easy to clean, stain, or seal. Fortunately, you have more choices than you think.
- 2x4s for small, compact decks
- 2x6s for more traditional, larger decks
- 5/4x6s, also known as five-quarter boards
If the answer on whether or not you can use 2×10 boards bothered you well, anything larger than a 2×6 is not a good idea for using as deck boards, which includes 2x8s right along with 2x10s.
When it comes to the smallest board on the list of “best boards,” 2x4s are the most limited. Like 2x10s are no good when it comes to width, 2x4s are no good when it comes to length. The longer they are, the more they tend to warp.
2×4 Deck Boards
When 2x4s warp, they tend to do so in a corkscrew manner, by twisting to the left or right. However, they are great for small decks and very low-profile decks, where the wood isn’t going to be cut long and everything is pretty small and compact.
2×6 Deck Boards
The most recognized deck boards, and the ones that are the most commonly used in deck construction, are the 2×6 variety. They are the “Goldilocks” of deck boards; not too long and not too wide but just right.
Like boards that are larger in width, 2×6 boards expand and shrink as well, however, it is more controllable. This is especially true if they are installed correctly, followed by a stain and seal.
5/4×6 Deck Boards
Probably the least known of the deck board options, the five-quarter boards primarily come in cedar and fir, pressure-treated when applicable. One advantage of five-quarter boards is that they are designed with rounded corners.
The rounded corners reduce the warping effect that pushes one side of the board up higher than the other. They also come with a rough side, which you would install facing down. It’s a unique option to choose from, especially if you want to get away from pine and go with something a little different.
Is There a Use for 2x10s in a Deck?
The primary use of 2x10s when building a deck is the installation of joists. The joists are the ribcage of the deck, the rows and rows of vertical boards, laid out across where the deck boards will go.
The deck boards will sit flat on top of the 2×10 joists and fastened to them all the way across. The joists connect to both the main beams and the posts that are installed in key areas. The posts are going to take the brunt of the deck weight and the joists will add quite a bit to that.
Also, 2x10s are not the most common boards used for joists on a deck. However, if you’re going to use 2x10s, that’s generally going to be the primary application for them.
Final Thoughts
Because of the aspects of expansion and shrinking in large boards, 2x10s are not the ideal boards to use for deck boards. While they will make good joists, the level of warping, cupping, shrinkage, and expansion you will get from using 2×10 size deck boards isn’t worth the wasted money and effort.
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