How fasteners are counted
Every board is fastened where it crosses a joist. So the count is:
rows × joists × fasteners per crossing
- Rows = width across the boards ÷ (board width + gap), rounded up.
- Joists = length along the boards ÷ joist spacing, rounded up, plus one.
- Fasteners per crossing = 2 for face screws, 1 for hidden clips.
For a 16 × 12 ft deck with 5-1/2" boards, a 3/16" gap and 16" joist spacing: 26 rows × 13 joists = 338 crossings, so 676 face screws or 338 hidden clips before any extra.
What the code and manufacturers say
The International Residential Code (R507.7) requires wood decking to be attached to each supporting member with at least two 8d threaded nails or two No. 8 wood screws (2021 IRC deck guide). For composite, follow the board manufacturer — TimberTech's guide, for example, calls for two screws per joist including end joints, no closer than 3/4" from the board edge (TimberTech installation guide).
Use fasteners rated for your decking and for treated lumber, and pre-drill near board ends where the manufacturer asks you to.
Butt seams add fasteners
Where two boards meet over a joist, each board end gets its own fasteners, so every seam adds one more fastening point. This page assumes single-board rows. For the exact count from your layout — including seams and doubled joists — use the deck board calculator.
Frequently asked questions
How many screws per deck board?
Two screws at every joist the board crosses. That’s the minimum the International Residential Code sets for wood decking (two No. 8 screws or two 8d threaded nails per support), and composite guides like TimberTech’s call for two screws per joist, including at board ends.
How many deck screws per square foot?
With 5-1/2" boards, a 3/16" gap and joists at 16" on center, it works out to about 3.5 screws per sq ft. At 12" on center it rises to about 4.6. Narrower boards or closer joists mean more screws.
How many hidden clips do I need?
About one clip per board at each joist — half the face-screw count. The first and last boards are usually face-screwed or use a starter clip. Hidden-clip boxes are often rated by square footage at 16" on center; Trex Hideaway, for example, rates 90 clips for 50 sq ft.
How do I take boards off a deck?
For screwed boards, clean out the screw heads and back them out with the right bit; a screw extractor deals with stripped heads. For nailed boards, work a flat pry bar or cat's paw under the board next to each joist, or cut the nails between board and joist with a reciprocating saw and a metal-cutting blade. Protect neighbouring boards with a scrap of wood under the bar. Boards held by hidden clips often have to come out from the end of the run, so check your clip system's instructions before you start.
How do I replace a deck board?
Remove the old board, then probe the joists underneath with a screwdriver — soft wood needs repair or a sister joist before you go further. Cut the new board so both ends land on the centre of a joist, set it with spacers to match the existing gap, pre-drill near the ends, and fasten it with two screws at every joist. Wood replacements will look brighter than weathered boards at first; composite colours can also differ between production runs.
Why add extra screws?
Some screws get dropped, strip or snap, and you may re-drive a few near board ends. 5% is a reasonable buffer for most projects.