Beadboard is sold as 1-inch-thick tongue-and-groove boards, offered with different widths between the beads. Which one you choose is a matter of personal taste; you can even mix them together to make a pattern. You can also get less expensive plywood beadboard, which comes in 4-by-8-foot sheets and can be nailed right to the joists, or faux beadboard made from cellular PVC, which is more stable than wood in an outdoor setting.
White pine 3 ¼-inch beadboard, 37 cents per ft.; hemlock 2 ½-inch beadboard, 63 cents per ft.; and aspen 1 ½-inch beadboard, 64 cents per ft.; all from Reliance Specialty Building Products. PVC beadboard, $1.55 per ft., from AZEK Trimboards. Plywood beadboard, $37 per sheet, from The Home Depot.