How it works
Rows are stacked across the deck from one edge. If more than one gap is left at the far edge, the last board is ripped to that width.
Joists run across the boards at the spacing you enter, with one at each end of the deck.
When the deck is longer than your longest board, rows are split so that every joint lands on a joist centre. With staggering on, neighbouring rows put their first joint one joist earlier.
Board pieces are passed to the cut list optimizer, and screws or clips are counted at every place a board crosses a joist.
What the calculator assumes
- Joist spacing, span, size and fixing method must follow the board manufacturer and your local building rules — the calculator does not check them.
- Board ends at a joint usually need extra support (double joist or blocking).
- No picture-frame border, stairs or cut-outs in this version.
Questions
- What joist spacing should I use?
- Use the value from the board manufacturer's installation guide. It differs between wood and composite boards and with diagonal laying.
- Why are joints staggered?
- Joints in a straight line weaken the look and concentrate load on one joist. Staggering spreads them across the deck.
Planning aid only. It does not size structural members or check loads — follow the manufacturer's instructions and your local building rules.