Deck screw quantity guide: how many screws per board and per deck
Updated April 26, 2026
Quick answer
Screws per square foot of deck
| Joist OC | Board width | Screws / 100 sqft |
|---|---|---|
| 12 in OC | 5.5 in (2×6) | ~470 |
| 16 in OC | 5.5 in (2×6) | ~350 |
| 16 in OC | 5.25 in (composite) | ~370 |
| 16 in OC | 3.5 in (2×4) | ~550 |
| 24 in OC | 5.5 in (2×6) | ~240 |
These counts assume two #8–#10 screws per board-to-joist intersection. Hidden-fastener systems use clips at every joist instead, see below.
Formula
Total screw count
face_screws = boards × joists_per_board × 2 Where: boards = ceil(deck_width_in / (board_width + gap)) joists_per_board = ceil(board_length_ft × 12 / OC_in) + 1 Example (12×16 deck, 5.5 in boards, 16 in OC): Boards = ceil(192 / (5.5 + 0.125)) = 35 boards Joists per 12-ft board = ceil(144/16) + 1 = 10 Total = 35 × 10 × 2 = 700 screws + 10% waste = 770 screws ≈ 1 lb box (350 ct) × 3
Worked example
12 × 16 PT deck, face-screwed, 16 in OC
Standard backyard deck, 5/4 × 6 in pressure-treated boards.
- 1. Boards needed35
- 2. Joists per 12-ft board10
- 3. Screws = 35 × 10 × 2700
- 4. + 15% waste805
- 5. Buy: 350-ct boxes3 boxes
→ 3 boxes of 2.5 in deck screws (~1,050 screws). Use 1.5 boxes per pass.
Screw length by board thickness
| Board type | Board thickness | Screw length |
|---|---|---|
| 5/4 wood (PT, cedar) | 1.0 in | 2.5 in |
| 2× wood (2×4, 2×6) | 1.5 in | 3.0 in |
| Composite (Trex, TimberTech) | 0.94 in | 2.5 in |
| PVC | 0.94 in | 2.5 in |
| Hardwood (ipe, cumaru), predrilled | 0.75 in | 2.0 in |
Rule: screw length must penetrate at least 1.25 in into the joist. Less than that and the board will pop loose under load and seasonal expansion.
Hidden fasteners (clip systems)
Composite boards usually offer hidden-fastener systems, clips that anchor between board edges into a slot on the side. Counts:
| Joist OC | Clips / 100 sqft |
|---|---|
| 12 in OC | 230 clips |
| 16 in OC | 175 clips |
| 24 in OC (composite-rated only) | 120 clips |
Hidden fasteners eliminate face-screw holes (cleaner look) but cost 2–3× more than screws and slow installation by 30–50%. Standard fastener bags ship 90 clips with 2 in screws included.
Screw types, what to buy
- Coated for treated lumber (ACQ-rated), required for PT decks. Standard zinc screws corrode in PT chemistry within 2 years.
- Stainless 305 / 316, for cedar, redwood, hardwoods, and any coastal install (within 1 mile of saltwater).
- Composite-color screws, head matches the board color (gray, brown, tan). Worth the extra $4/lb for visible decks.
- Star-drive (T20/T25) heads, never Phillips. Phillips cams out and strips. Star drive holds bit perfectly.
Common mistakes (and how to avoid them)
✗ Using one screw per joist crossing instead of two.
Fix: Single-screw decks twist boards and develop squeaks within a year. Always two screws per joist crossing, one near each edge of the board.
✗ Buying standard zinc screws for PT lumber.
Fix: ACQ pressure-treatment chemistry corrodes zinc within 2 years, then the screws snap. Always buy ACQ-rated coated screws or stainless.
✗ Using 2 in screws on 5/4 boards.
Fix: 2 in screws penetrate the joist by only 1 in, not enough. Use 2.5 in minimum on 5/4 boards. Skipping this causes board pop in year 2.
✗ Screwing too close to the board edge.
Fix: Maintain 1 in from the board edge to prevent splitting. On hardwoods, also pre-drill every screw, even with star-drive bits.