How many deck screws per square foot?
Budget about four deck screws per square foot at 16" joist spacing — two per board at every joist it crosses, plus breakage. Counts for the common deck sizes.
About 3.9 screws per square foot, at 16" joist spacing.
A 12' × 16' deck in 5/4 x 6 (5 1/2" wide) works out at 744 screws — 26 rows crossing 13 joists, two at every crossing, plus 10% for the ones that snap or cam out.
How that is worked out
- Two screws hold each board down at each joist it crosses. That is the rule the count comes from, not a rate per square foot.
- This deck has 26 rows of 5/4 x 6 (5 1/2" wide) and 13 joists at 16" on centre, so 26 × 13 × 2 = 676 screws in the field.
- Add 10% for breakage and you are buying 744. Over 192 ft² that is the 3.9 per square foot in the headline — a useful cross-check, never the thing to count with.
Deck screws by deck size, 5/4 x 6 (5 1/2" wide) at 16" centres
| Deck size | Square feet | Board rows | Joists | Screws (with 10% spare) |
|---|---|---|---|---|
| 8' × 10' | 80 | 17 | 8 | 300 |
| 10' × 12' | 120 | 22 | 10 | 485 |
| 12' × 12' | 144 | 26 | 10 | 572 |
| 12' × 16' | 192 | 26 | 13 | 744 |
| 14' × 20' | 280 | 30 | 16 | 1056 |
| 16' × 20' | 320 | 34 | 16 | 1197 |
Worth knowing
- Joist spacing changes this more than anything else. Going from 16" to 12" centres — which some composite decking requires, and every diagonal board pattern does — adds roughly a third more screws.
- Hidden fasteners are a different count entirely: one clip per board per joist rather than two screws, plus a screw into each clip. Check the maker's coverage figure, which is usually given per square foot on the box.
- Buy deck screws by the pound or the bucket rather than the box for anything over a small deck. Screws are cheap next to a second trip.
- Use screws rated for the preservative in your lumber. Modern treatment is corrosive to plain steel and will eat an unrated screw off inside a few seasons.
Work out your own numbers
- Deck and fence takeoff
Boards, joists, posts, pickets, screws and bags of concrete, with the gaps between boards properly counted.
- Fastener calculator
Screws or nails for a sheet good on an edge-and-field pattern, with the box count to buy.
Related questions
- How many screws per deck board?
- Two at every joist the board crosses — one near each edge, set in about 3/4" from the edge and never at the very end of the board. One screw per joist lets the board cup and rock; three is fussy and puts a hole where the board needs to move.
- How many deck screws do I need for a 12x16 deck?
- Around 750 for the decking itself at 16" joist centres, using 5/4x6 boards — 26 rows crossing 13 joists, two screws at each crossing, plus 10% spare. That is before anything for the framing, the rim joists, the stair treads or the railing, all of which use heavier structural screws or bolts rather than deck screws.
- What length deck screws should I use?
- 2 1/2" for 5/4 decking and 3" for a full 2x board. The rule behind both is that the screw should reach at least as far into the joist as the thickness of the board it is going through, and further is better as long as it does not come out the other side of a 1 1/2" joist.