25-35 screws per m² for boards at 400mm joist centres with two screws per intersection. A 4m x 3m deck at 12m² needs roughly 300-400 screws — buy a 500 tub.
| Deck size | Screws needed | Practical buy |
|---|---|---|
| 4m × 3m (12 m²) | 300-420 screws | Buy 500 tub |
| 5m × 4m (20 m²) | 500-700 screws | Buy 1000 tub |
| 6m × 4m (24 m²) | 600-840 screws | Buy 1000 tub |
| 3m × 3m (9 m²) | 225-315 screws | Buy 500 tub |
Two screws per board width per joist stops cupping and lifting. One screw lets the board twist as it seasons; two hold it flat.
Stainless (A2 at minimum, A4 near coast) for timber. For composite, use the manufacturer's coloured composite screws — coated screws can react with composite cores.
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