Deck board staggering calculator
For a 20 ft run of deck boards 12 ft wide, on joists 16 inches apart, with 16 ft and 12 ft boards, the pattern below puts every seam on a joist and at least two joists from the seams beside it: buy 16 × 16 ft and 28 × 12 ft. Type your deck to plan yours.
Boards to buy
16 × 16 ft and 28 × 12 ft
Boards to buy for 26 rows of 5½ in boards across a 20 ft run.
- 30 seams, each on a joist, at least 2 joists from the seams in the next row.
- 592 linear feet of boards for 520 feet laid: about 12% left over.
Each board rests on at least three joists, as the American Wood Council’s deck guide asks. Your decking maker’s rules come first.
Every row, board by board
- Row 1: 16 ft + 4 ft
- Row 2: 13 ft 4 in + 6 ft 8 in
- Row 3: 10 ft 8 in + 9 ft 4 in
- Row 4: 8 ft + 12 ft
- Row 5: 5 ft 4 in + 14 ft 8 in
- Row 6: 2 ft 8 in + 13 ft 4 in + 4 ft
- Row 7: 13 ft 4 in + 6 ft 8 in
- Row 8: 10 ft 8 in + 9 ft 4 in
- Row 9: 8 ft + 12 ft
- Row 10: 5 ft 4 in + 14 ft 8 in
- Row 11: 2 ft 8 in + 13 ft 4 in + 4 ft
- Row 12: 13 ft 4 in + 6 ft 8 in
- Row 13: 10 ft 8 in + 9 ft 4 in
- Row 14: 8 ft + 12 ft
- Row 15: 5 ft 4 in + 14 ft 8 in
- Row 16: 2 ft 8 in + 13 ft 4 in + 4 ft
- Row 17: 13 ft 4 in + 6 ft 8 in
- Row 18: 10 ft 8 in + 9 ft 4 in
- Row 19: 16 ft + 4 ft
- Row 20: 13 ft 4 in + 6 ft 8 in
- Row 21: 10 ft 8 in + 9 ft 4 in
- Row 22: 8 ft + 12 ft
- Row 23: 5 ft 4 in + 14 ft 8 in
- Row 24: 2 ft 8 in + 13 ft 4 in + 4 ft
- Row 25: 13 ft 4 in + 6 ft 8 in
- Row 26: 10 ft 8 in + 9 ft 4 in
The rules the pattern follows
Every board end lands on the middle of a joist, so both boards at a seam get support. Every board spans at least two joist bays, resting on three joists or more. Seams in neighboring rows stay the distance you choose apart, two joists by default, and a seam never sits on the same joist as the seam two rows back, so no line of joints runs across the deck.
Check your decking maker
Composite and PVC boards come with their own rules: some need a double joist or blocking under every butt joint, and many need a small gap at board ends that depends on the temperature on the day you lay them. Follow the installation guide for your boards where it differs from this plan.
Longer boards, fewer seams
Adding a longer board length usually cuts the number of seams and the waste. Offcuts long enough to span two joist bays are reused in the plan before a new board is bought.