How the clips and screws are counted
Every row of boards crosses every joist. Hidden clips sit in the gaps between rows, one at each joist, and each clip holds the edges of the two boards beside it. The first row’s outer edge takes start clips, and the last row is face-screwed. Butt joints add two fasteners each. Rows and butt joints are counted the same way as in the deck board calculator.
Worked example: a 16 × 12 ft Trex deck, joists 16 in apart, Hideaway clips
- Joists: 192 ÷ 16 = 12 bays, so 13 joists under every row.
- Rows: (144 + 0.1875) ÷ 5.6875 = 25.35, so 26 rows of 5½ in boards with 3/16 in gaps.
- Hidden clips: 25 gaps between rows × 13 joists = 325. The 16 ft boards span the deck, so no butt joints.
- Start clips: 13 along the first row. The last row: 2 × 13 = 26 face screws.
- Trex’s coverage: a box of 90 for 50 sq ft is 1.8 per sq ft, and 192 × 1.8 = 345.6, so 346 clips: 4 boxes.
The joists are counted from one end of the row: when the length isn’t a whole number of bays, the shorter last bay still ends on a joist, since the board ends need one under them.
Board by board, or by the maker’s coverage
Clip makers sell by deck area. Trex’s box of 90 Hideaway clips covers 50 sq ft at 16 in on center, 1.8 clips per sq ft. Counting one clip per board at each joist gives fewer: 144 ÷ (5 11/16 × 16) = 1.58 clips per sq ft for 5½ in boards with 3/16 in gaps, or 79 for 50 sq ft. Trex’s figure is about 14% more. Treat the difference as an allowance for butt joints, the joist at the far end of every row and the odd dropped clip. The calculator shows both counts, and the packs cover whichever is larger.
| Fasteners per sq ft | 12 in | 16 in | 24 in | Packs |
|---|---|---|---|---|
| Trex Hideaway clips | — | 1.8 (90 per 50 sq ft) | — | 90 |
| TimberTech CONCEALoc clips | — | 1.75 (175 per 100 sq ft) | — | 175, 1,750 |
| Fiberon Phantom Universal clips | 2.1 | 1.75 | 1.1 | 900 (500 sq ft) |
| CAMO edge clips | 2.33 (117 per 50 sq ft) | 1.8 (90 per 50 sq ft) | — | 90, 450, 900 |
| CAMO edge screws | — | 3.5 (350 per 100 sq ft) | — | 100, 350, 700, 1,750 |
Columns are joist spacing on center. Fiberon’s rates are its chart’s 100 sq ft row (210, 175 and 110 clips); CAMO’s chart gives 583, 699 and 1,165 clips at 12 in for 250, 300 and 500 sq ft. A dash means the maker publishes no figure for that spacing; the calculator then says so and buys packs for the board-by-board count. Brand names identify products only.
Start clips, the last row and butt joints
The first row has no board before it, so its outer edge is held with start clips, one at each joist. Fiberon sets its starter clips at least 1/4 in from the wall. The last row has no board after it to clip to, so it is face-screwed, two screws at each joist. With screws instead of clips, every row is fastened the same way: two per board at each joist.
A butt joint needs fastening on both board ends, over a doubled joist or blocking. TimberTech puts four clips at a butt joint, two more than at an ordinary joist, and with screws each end gets its own two, so every joint adds two fasteners. Boards as long as the deck avoid joints: on a 20 × 12 ft TimberTech deck with joists 16 in apart, 12 ft boards make 26 joints and 452 clips, while 20 ft boards make none and need 400.
Hidden clips also set the gap between rows. TimberTech’s CONCEALoc and Fiberon’s Phantom Universal clips both leave 3/16 in, the same as Trex’s side gap. Under wood boards gapped 1/8 in, the calculator points out the difference.
Joist spacing
Closer joists mean more crossings, so more fasteners. A 16 ft row crosses 17 joists at 12 in on center, 13 at 16 in and 9 at 24 in, so the 16 × 12 ft Trex deck takes 425, 325 or 225 hidden clips.
The boards set the limit. Trex wants joists 16 in on center under its 1× boards on a home’s deck, and 12 in on commercial decks. TimberTech allows 16 in at most, and 12 in for any angled or commercial install. Fiberon calls for 16 in on homes, 12 in for diagonal boards and 12 in on stairs. Only 2× wood decking spans 24 in, and the calculator warns when the joists are farther apart than the chosen boards allow.
Face screws
Trex, TimberTech, Fiberon and the American Wood Council’s DCA 6 agree on two screws per board at every joist. On the 16 × 12 ft deck that is 2 × 26 × 13 = 676 screws, or 3.52 per sq ft. CAMO rates its edge screws at 350 per 100 sq ft, 3.5 per sq ft, so the two counts land close together.
Choose “Face screws” in the calculator to count them for your deck. Butt joints add two screws each, since both board ends get their own pair.
Questions people ask
How many hidden deck fasteners do I need for a 12×16 deck?
With 5½ in boards and 3/16 in gaps running the 16 ft way on joists 16 in apart: 26 rows × 13 joists, so 325 hidden clips, 13 start clips and 26 face screws for the last row. Trex’s rate of 90 clips per 50 sq ft gives 346 for 192 sq ft, which is 4 boxes of 90. Run the boards the 12 ft way and it’s 34 rows × 10 joists: 330 clips, 10 start clips and 20 screws.
How many screws go in each deck board?
Two at every joist. A 16 ft board on joists 16 in apart sits on 13 joists, so it takes 26 screws; with joists 12 in apart it sits on 17 and takes 34. Where two boards meet at a butt joint, each end gets its own two screws.
Do hidden clips work with joists 24 in apart?
Not under composite boards on a home’s deck: Trex, TimberTech and Fiberon all limit their boards to joists 16 in on center. 2× wood decking can span 24 in. Fiberon’s chart gives 110 Phantom Universal clips per 100 sq ft at 24 in, against 175 at 16 in.
How are the first and last boards fastened?
The first board sits on start clips, one at each joist, and the clips between the first and second rows hold its other edge. The last board has nothing beyond it to clip to, so it is face-screwed, two screws at each joist: 26 screws along a 16 ft row with joists 16 in apart.
How many clips come in a box?
Trex Hideaway: 90 clips for 50 sq ft. TimberTech CONCEALoc: 175 clips for 100 sq ft, or 1,750 for 1,000 sq ft. Fiberon Phantom Universal: a bucket of 900 for 500 sq ft. CAMO edge clips: 90, 450 or 900, for 50, 250 or 500 sq ft. All of these are for joists 16 in on center.
Why is the maker’s count different from the board-by-board count?
The makers sell by area. For 50 sq ft of 5½ in boards with 3/16 in gaps on joists 16 in apart, one clip per board at each joist works out to 79, and Trex’s box for that area holds 90. The board-by-board count can be the higher one, too: 2×6 wood boards on joists 24 in apart take 225 clips on a 16 × 12 ft deck, where Fiberon’s 24 in rate gives 211. The calculator buys packs for the larger of the two.
Sources for the numbers on this page
- Trex — Hideaway hidden fasteners, box of 90 (coverage) · checked October 3, 2026
- Trex — Decking installation guide, 2026 edition (gaps, spans, fastening, stairs) · checked October 3, 2026
- TimberTech — CONCEALoc hidden fasteners (coverage) · checked October 3, 2026
- TimberTech — Pro tips: installing decking with CONCEALoc (clips at butt joints) · checked October 3, 2026
- TimberTech — Composite decking installation guide, REV 09/23 · checked October 3, 2026
- Intertek, for TimberTech — CCRR-0128 code compliance research report: decking spans and stairs (PDF) · checked October 3, 2026
- Fiberon — Hidden deck fastener FAQ (fasteners by deck area and joist spacing) · checked October 3, 2026
- Fiberon — Phantom Universal hidden fasteners (3/16 in gap) · checked October 3, 2026
- Fiberon, via The Home Depot — Phantom Universal hidden fastener bucket of 900 (500 sq ft) · checked October 3, 2026
- Fiberon — PE decking fastening instructions, FIB-0354-LIT 1/22 (distributor copy, PDF) · checked October 3, 2026
- ICC Evaluation Service — ESR-4947: Fiberon composite decking, revised 08/2026 (PDF) · checked October 3, 2026
- CAMO — 2024 catalog: clip and screw coverage by deck area (PDF) · checked October 3, 2026
- American Wood Council — DCA 6: Prescriptive residential wood deck construction guide (2015 IRC edition) · checked October 3, 2026
Corrections and updates are logged on the sources page.