Deck board spacing

Q: What’s the proper spacing for deck boards? I’m making plans to rebuild three partially rotten wooden decks this spring. Right now the boards are spaced close enough to gather all kinds of rot-promoting gunk. The decks are less than 18 inches above ground. Is 1/2-inch board spacing too wide?

A: Deck spacing is pretty important for getting the most of deck life and wood. You'll find that 1/4-inch is usually adequate for drainage and gunk resistance, though composite deck boards need a little more since they expand and contract with changes in temperature. You can certainly reinstall your boards with 1/2-inch spacing, but it won't look quite as nice as it should. Also, since you’re rebuilding, consider doubling up joists in places where deck board joints occur. Leaving 1/2-inch of space between each new joist and its neighbour allows you to space the ends of deck boards for ventilation. Eliminating end-to-end board contact extends deck life more than any other design feature.