What joist spacing do I need?
16 in on centre is standard for perpendicular boards; use 12 in for diagonal patterns or most composite decking, which is less rigid than wood.
Calculate deck boards, joists, and fasteners needed for any deck size. Enter dimensions and board size for accurate material lists.
Boards = deck area ÷ (board width + gap) coverage per linear ft. Joists = ceil(deck length ÷ spacing) + 1. Add 10% waste for cuts.
A 12 × 16 ft deck (192 sq ft) with 5.5 in boards and 1/4 in gaps needs about 400 linear feet of decking, plus 13 joists at 16 in on centre.
16 in on centre is standard for perpendicular boards; use 12 in for diagonal patterns or most composite decking, which is less rigid than wood.
1/8 to 1/4 in. Wet pressure-treated lumber shrinks as it dries, so install it tighter; kiln-dried and composite boards should be gapped at install.
About 350 screws per 100 sq ft with two per joist crossing. Buy 10% extra — stripped heads and mis-drives are unavoidable.