Deck Board Gap and Spacing Chart
The gap between deck boards is not a preference — it is what lets water drain and lets wood move with humidity. Too tight and boards cup; too wide and debris collects.
| Board type | Gap | Notes |
|---|---|---|
| 5/4 pressure-treated pine | 1/8" – 1/4" | Most common; 1/4" is typical for hot climates |
| 2×6 pressure-treated | 1/4" | Wider board, wider gap |
| Composite decking | Follow manufacturer | Most composites specify 1/4" and expand more than wood |
| Cedar or other dense hardwood | 1/8" – 1/4" | Moves more than softwood with humidity |
| Wide plank (8"+) | 1/4" and up | Cupping risk increases with width |
Joist spacing by board thickness
| Board | 16" OC | 24" OC | Max span |
|---|---|---|---|
| 5/4 (1.25") | Standard | May be OK | 16 ft typical |
| 2×6 (1.5") | Standard | Yes | 16 ft typical |
| 2×8 (2") | Yes | Yes | 20 ft possible |
Always check the manufacturer's span table for the specific product. The joist span tables on WoodCalc are conservative SPF values, not a substitute for a grade stamp.
Screw placement
- Two screws per board at each joist crossing is the structural minimum.
- Stagger screws 1–2 inches apart to split the risk of splitting.
- Keep screws 2 inches from the board edges to avoid blowout.
- End joints need a joist behind them — never butt two boards together mid-span.
Where to buy
Compare current pricing across major suppliers — prices vary by region and season.
Related tools
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