Typically, composite and low-maintenance deck boards are available in 12 foot, 16 foot, and 20 foot lengths.
You may find that chain home-improvement retailers have other lengths like 8 foot and 10 foot available, which makes loading and transporting them easier. The flipside of this is that building a large, seamless deck is nearly impossible without multiple mullions or random seaming the boards.
Some manufacturers may offer lengths like 22 or 24 footers, but they are usually special order, and can be difficult handle due to how much they bend.
Cedar and treated deck boards come in many sizes between 8 feet and 24 feet, due to what can be cut out of a tree efficiently and transported easily.
Ipe decking is often bought and sold in "random lengths" meaning you'll get an assortment of sizes between 8 feet and 20 feet long. This makes more efficient use of the already expensive "exotic" material, keeping the price slightly lower, but will require that the deck be random seamed. Random-seaming is a more common layout method for Ipe decks, because of its cost, and its dimensional stability. Having butt-to-butt seams on PVC or composite deck boards sometimes leads to issues with expansion and contraction, like gaps opening up or unclean seams.
Check out our "estimating materials" page if you're curious about how to efficiently use these board lengths on your project.
