How deck boards are counted
Divide the deck width (perpendicular to the boards) by the board's face width plus the gap to get the number of rows. Multiply rows by deck length for linear feet, add waste, and divide by your board length.
Example: 16 × 12 ft deck, 5.5 in boards with 1/8 in gaps: 144 ÷ 5.625 = 25.6 → 26 rows × 16 ft = 416 linear ft. Plus 10% = 457.6 ÷ 16 = 28.6 → 29 boards.
Gaps and materials
- Pressure-treated pine is often installed tight because it shrinks as it dries; follow the lumber supplier's advice.
- Composite decking: use the manufacturer's spacing (commonly around 3/16 in) and hidden fasteners where specified.
Fasteners
Face-screwing uses two screws at every joist. With joists 16 in on center, that's about 350 screws per 100 sq ft—buy coated or stainless screws rated for treated lumber.