Decking calculator
Calculate how many deck boards, joists, and metres of timber you need for your deck.
Deck size
m
m
Boards
Wickes recommends 5-8mm expansion gap. For composite boards, follow manufacturer's guidance.
Frame & waste
Wickes recommends 400mm centres. Check the TDCA table below for maximum spans.
Wickes recommends 10% extra for errors, damage, and obstacles.
TDCA maximum board span table
This table from the TDCA Code of Practice shows maximum joist centres for different board sizes and timber grades (3.0 kN/m² design load). Your joist spacing should not exceed these values.
| Board (mm) | C16 | C22 | C24 | D30 (Oak) |
|---|---|---|---|---|
| 95 × 22 | – | – | – | 300 |
| 95 × 34 | 450 | 500 | 550 | 550 |
| 120 × 22 | – | – | – | 350 |
| 120 × 27 | 400 | 425 | 450 | 450 |
| 120 × 34 | 500 | 550 | 600 | 600 |
| 145 × 22 | – | – | – | 400 |
| 145 × 27 | 400 | 425 | 450 | 450 |
| 145 × 34 | 500 | 550 | 600 | 600 |