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Deck planning tool
Deck board, joist and clip calculator
Give it a deck size and it gives you a Tarimatec take-off: 2,500 mm boards, aluminium joist in linear metres at 350 mm centres, hidden clips at 25 per square metre, substrate anchors at 500 mm, perimeter fascia and fixing screws. Every rule it applies is printed underneath so you can check the arithmetic rather than trust it.
The rules this calculator applies
None of these are Zinodeck house rules. They come from Tarimatec's Manual Tecnico 2023 and the tested product data, and they are the same rules the manufacturer's warranty assumes.
| Rule | Value used | Source |
|---|---|---|
| Board coverage pitch, hollow | 150 mm board + 5 mm side gap = 155 mm | Manual Tecnico 2023 |
| Board coverage pitch, solid | 149.2 mm board + 5 mm side gap = 154.2 mm | Manual Tecnico 2023 |
| Board length | 2,500 mm, tolerance 10 mm. Lengths to 4,000 mm are a special order above 100 square metres. | Manual Tecnico 2023 |
| Coverage | Tarimatec quotes about 6.5 boards per square metre. Read precisely that is 6.45 linear metres of board per square metre at the 155 mm pitch, which is 2.58 full 2,500 mm boards per square metre. | Manual Tecnico 2023 |
| Joist spacing | 350 mm centres maximum; 250 mm in tropical conditions. The calculator never exceeds 350 mm. | Manual Tecnico 2023 |
| Joist section | Aluminium 30 x 50 mm, alloy EN AW 6005 T6 | Manual Tecnico 2023 |
| Perimeter | A closed frame runs the full perimeter of the deck, in addition to the field joists | Manual Tecnico 2023 |
| Cross members over timber | Where the aluminium joist sits on a timber frame, cross members at 1,000 mm centres or closer | Manual Tecnico 2023 |
| Hidden clips | 25 clips per square metre. H clip in AISI 304L stainless; 316L within reach of salt air. | Manual Tecnico 2023 |
| Substrate anchors | The joist is anchored down at 500 mm centres along its length | Manual Tecnico 2023 |
| Screws | DIN 7504P A2 self-drilling, 4.2 x 25 mm, one per clip | Manual Tecnico 2023 |
| Fascia | 180 x 10 mm fascia profile, cut from 2,500 mm lengths | Tarimatec accessory range |
| Weight on the structure | 17.1 kg per square metre hollow, 23.9 kg per square metre solid, boards only | EPD S-P-07588 |
How each number is worked out
Boards
Deck area divided by the coverage pitch gives the linear metres of board. The waste allowance is added to that figure, and the result is divided by 2.5 m and rounded up to a whole board. A 6.0 x 4.0 m deck is 24.0 square metres, which is 154.8 linear metres of board; add 5 per cent and you need 66 boards.
Joist
Joists run across the boards. The calculator divides the dimension the boards run along by 0.35 m, rounds up, and adds one to close the ends, then multiplies that count by the length of each joist. The closed perimeter frame is counted separately and added on top, which is why the joist total is always higher than a naive spacing calculation. On the same 6.0 x 4.0 m deck with boards running along the 6 m length: 19 joist runs of 4.0 m is 76.0 m, plus 20.0 m of perimeter frame, for 96.0 m of aluminium.
Clips, anchors and screws
Clips are a flat 25 per square metre. Anchors are counted along every joist run and around the perimeter frame at 500 mm centres, with one at each end. Screws are one per clip plus one per anchor, with 5 per cent added, because self-drilling screws get dropped through the deck and snapped off at a rate that surprises first-time installers.
Cross members
If you tell the calculator the aluminium sits on a timber frame rather than on concrete, slabs or adjustable pedestals, it adds timber cross members at 1,000 mm centres running parallel to the boards, because the aluminium joist has to be supported and fixed at that interval rather than floating between widely spaced bearers.
What the calculator does not include
- Prices. Quantities first, money later, on the cost calculator or in a written quote.
- Pedestals, footings, bearers, ground preparation, membranes or drainage.
- Start and finish clips at the first and last board, stair nosings, corner trims or end caps. Those are counted from the drawing, not from the area.
- Structural design. Joist spacing is a decking rule; bearer sizing, pedestal loading and anything elevated or on a roof need a designer who has seen the loads.
- Non-rectangular decks. Cut-outs, mitres, picture framing, herringbone patterns and multi-level decks all push the board and clip count above what a rectangle predicts. Use the 8 per cent waste setting and then check against a drawing.
The two mistakes that wreck a take-off
Carrying over 400 mm joist spacing from timber decking
Timber deck boards at 400 mm centres feel normal to most Canadian builders, and 600 mm is common for wider softwood. A Tarimatec board is specified at 350 mm and no wider. At 400 mm the board is unsupported past its rating, the deck feels soft underfoot, and you are outside the conditions the manufacturer's warranty, administered in Canada by Zinodeck, was written against. Roughly one extra joist run in every eight is the whole difference, and it is far cheaper to buy than to retrofit.
Forgetting the perimeter
The closed frame around the deck is easy to leave out of a spreadsheet and it is a fifth of the aluminium on a small deck. On the 24 square metre example it is 20 of the 96 linear metres. If the take-off you were given has field joists only, it is short.
Before you order
Take a site measure rather than a drawing measure, check the result against Tarimatec's installation manual, and read the expansion gap guide before you cut anything. Boards are import to order, so a short order is not a same-week fix: plan on 8 to 12 weeks from a confirmed order.
Related: the board estimator if you only need a board count, the expansion gap guide for end gaps, edge and stair details for the perimeter, the installation guide for the sequence, and the cost calculator once the quantities are settled.
See the colour before you commit the quantity
A take-off is only half the decision. No screen renders a composite surface honestly, so order paid sample tiles and look at them in your own light, wet and dry, before a whole deck goes to one colour. Samples ship from Vaughan, Ontario in 5 to 10 business days.
Order samples