Deck Materials & Cost: Boards, Joists and Screws

Count the decking boards

Boards run across the joists. The number of rows is the deck width (in inches) divided by the board width plus the gap. With 5.5-inch boards and a 1/8-inch gap, a 12 ft width needs about 26 rows — so 26 full-length boards before waste.

Try it Deck Calculator → Estimate decking boards, joists and screws for a deck from its size and board spacing.

Joists and screws

Joists usually sit 16 inches on center (12 inches for diagonal decking or heavy loads). Fasten with two screws per board at every joist — a 12 × 12 deck at 16-inch spacing works out to roughly 520 screws.

• Leave a small gap between boards for drainage and movement.
• Buy 10% extra boards for cuts, culls and future repairs.
• Use exterior-rated screws and joist hangers; flash the ledger against the house.

What drives the cost

Decking material is the biggest lever: pressure-treated pine is cheapest, cedar mid-range, composite the most expensive up front but lowest maintenance. Framing, footings, railings and labor are on top of the board count our calculator gives you.