Sheet yield is decided by the width, not the area
Area is the wrong way to think about sheet goods. A 12 by 3 ft deck is 36 sq ft and a 4 by 8 sheet is 32, so on area you would expect a bit over one sheet per deck. What actually happens is that a 3 ft wide strip comes out of a 4 ft sheet exactly once — the leftover foot is not another strip — and an 8 ft strip does not reach 12 ft, so each deck needs two of them. One strip per sheet, two strips per deck: two sheets per deck, six for three decks, 192 sq ft bought against 108 used. Forty-four percent thrown away.
Turn the sheet. Cut 3 ft strips across the 8 ft direction and you get two per sheet, each 4 ft long. A 12 ft deck now needs three of them, so nine strips for three decks, which is five sheets — 160 sq ft, 52 wasted, 32.5 percent. One sheet saved and about thirty square feet less waste, at the price of two joints per deck instead of one.
| Cut direction | Strips per sheet | Strips per deck | Sheets for 3 decks | Bought | Offcut | Joints per deck |
|---|---|---|---|---|---|---|
| Along the 8 ft length | 1 | 2 | 6 | 192 sq ft | 84 sq ft | 1 |
| Across, 4 ft strips | 2 | 3 | 5 | 160 sq ft | 52 sq ft | 2 |
The calculator works both out and leads with whichever takes fewer sheets, breaking a tie on joints. It does not tell you which to choose, because a joint in a deck is a structural question and this is a materials page.
Slats and cross members are fencepost counts
Both are the classic off-by-one. Slats at 12 in on centre along a 12 ft deck is 144 divided by 12, which is 12 gaps and therefore 13 slats — one at each end and eleven between. Cross members at 16 in on centre along the same 12 ft is 144 over 16, which is 9 spaces and 10 members. Get this wrong in the buying direction and you are one piece short on every panel in the set, which on three panels is three trips or three excuses.
The stock arithmetic is the same shape as the pipe cut list on the jump page: a 3 ft slat comes out of an 8 ft length twice, not two and two thirds, so 39 slats at 2 per length is 20 lengths, not 15. The calculator does the whole-piece division rather than dividing footage.
Coating covers less than you think
A grit-loaded non-slip coating is not paint and does not spread like paint. The coverage figure belongs on the product data sheet for whatever you are buying, which is why it is a field. What the page adds is the edges: the face of a 12 by 3 deck is 36 sq ft, but a 10 in band round the perimeter is another 25, so the real coverage per face is closer to 61 than 36. Two coats on three panels at 60 sq ft a gallon is 6.1 gallons, so seven tins, and reaching for four because the faces alone total 108 sq ft is how a build stalls halfway through the second coat.
Weight, and why it belongs in a take-off
Sheet weight per square foot times deck area gives what the surface alone weighs, before framing, slats, coating and hardware. A 12 by 3 deck out of a sheet quoted at 46 lb is about 52 lb of sheet material, and that is the optimistic half of what two people end up carrying. Knowing it in advance is the difference between a two-person lift and a four-person one, and equipment moved by hand across soft ground is a genuine hazard rather than a rhetorical one.
Everything above is materials. How the obstacle is built, what carries the joints, how it is fixed together, how it is inspected and when it is retired follow the specification published by the organization you compete under and the instructions of whoever made the equipment. A contact obstacle failing under a dog at speed is the reason that is not negotiable and not something a calculator gets a say in.
Where this hands off
Pipe-framed equipment — jumps, weaves, tunnel fabric area — is on the jump and weave pipe take-off calculator, which packs the cut list into sticks. The ring these end up in is the agility ring size calculator, and the footing under it is the arena footing calculator. For general sheet-goods coverage on a floor rather than a panel, subfloor sheathing handles the same yield question at building scale.
Questions people ask
What size should a contact obstacle deck be?
That comes from the specification of the organization you compete under, or from the maker of the equipment you are copying, and it is not on this page. Dimensions differ between organizations and they change. The take-off is dimension-neutral: type in whatever the specification says and it hands back sheets, framing, slats, coating and weight for those figures.
Which cutting direction should I choose?
The calculator shows both and leads with the one that takes fewer sheets, but the choice is not purely economic. Cutting across the sheet usually saves material and adds a joint per panel, and where a joint falls in a panel and what carries it underneath is a structural decision for whoever specified the obstacle. If the specification or the plan you are working from says anything about joints, that outranks the sheet count.
Why is the slat count one more than length divided by spacing?
Because slats are objects and spacings are gaps between them, and there is always one more object than gap in a line with both ends filled. Twelve feet at 12 in on centre is 12 gaps and 13 slats. The same arithmetic catches people out on fence pickets, studs, balusters and cross members, and it catches them out in the same direction every time — one short.
Does the coating figure include the underside?
No. It covers the face plus a 10 in band around the perimeter as an edge allowance, on the assumption that the running surface and the edges are what get coated. If you are coating both faces, double the panel count or double the coats — either produces the same number. The coverage rate itself must come from the data sheet for the product, since grit-loaded coatings vary enormously and the tin does not spread like paint.
Is the weight figure the weight of the finished obstacle?
No, and the page says so where it prints it. It is the sheet material only, derived from the sheet weight you entered. Framing, slats, coating, fasteners, hinges, adjusters and any support structure are all on top, and a finished panel will comfortably exceed it. Treat the number as a floor for planning the lift, not as a specification.