Short answer: the seams use up about 3 to 6 inches of the coil. A 20-inch coil makes a 16-inch, 1.5-inch snap-lock or mechanical panel. A 24-inch steel coil makes an 18-inch, 2-inch mechanical panel. To estimate coil, divide coil width by panel coverage. Then multiply the roof area by that number and add waste.
Coverage, not coil width, sets the panel count
Coverage is the finished width of one panel, seam to seam, once panels lock together. The roll former bends the coil’s edges into the two seam legs. Whatever the seams use comes out of the coil width.
Count panels with coverage. Order coil by width. Mix the two up and the whole estimate is off.
Coil width and coverage by profile
Sheffield Metals publishes how much coil each of its panels uses. The seam types match common New Tech Machinery (NTM) profiles, listed for reference. NTM profiles are adjustable, so check the actual width with your machine.
| Seam | Sheffield panel | Coverage | Coil width | Coil used by seams | Coil per sq ft of roof |
|---|---|---|---|---|---|
| 1″ snap-lock, nail flange (NTM FF100 type) | SMI 1.0″ FF SnapLock | 16″ | 20″ (24″ max) | 4-1/16″ | 1.25 |
| 1″ mechanical (NTM SS100 type) | SMI 1.0″ Mechanical Seam | 17″ | 20″ max | 3″ | about 1.18 |
| 1.5″ snap-lock with clips (NTM SS450 type) | SMI 1.5″ SnapLock 450+ | 16″ | 20″ | 4-1/8″ | 1.25 |
| 1.5″ snap-lock with clips | SMI 1.5″ SnapLock 550 | 19″ steel, 15″ aluminum | 24″ max | 5-1/8″ | coil width ÷ coverage |
| 1.5″ mechanical (NTM SS150 type) | SMI 1.5″ Mechanical Seam | 16″ | 20″ | 4″ | 1.25 |
| 2″ mechanical (NTM SSQ200 type) | SMI 2.0″ Mechanical Seam | 18″ steel, 16″ aluminum | 24″ steel, 22″ aluminum | 5-13/16″ | 1.34 (steel) |
Three things stand out. Snap-lock seams use a little more coil than a 1-inch mechanical seam. The 2-inch mechanical seam uses the most. And aluminum versions can run narrower than steel because of their engineering.
Sheffield adds a useful rule. You may use a heavier gauge and a narrower panel than the tested one, and clip spacing stays the same. Going wider than the tested width is a different matter. Ask the panel maker first.
Seam choice also sets slope and warranty limits
Coverage is only one reason to pick a profile. The same Sheffield cut sheets list minimum slopes and warranty eligibility.
- 1″ FF snap-lock: 3/12 minimum slope. It fastens through a slotted flange with no clips. Sheffield does not approve it for weathertight warranties.
- 1.5″ SnapLock 450+: 3/12 minimum slope, clips per engineering, approved for weathertight warranties.
- 1.5″ SnapLock 550: 2/12 minimum slope in Sheffield’s engineered system.
- 1.5″ and 2″ mechanical seams: 2/12 minimum slope. Below 2/12, Sheffield asks you to contact its technical department.
Stiffening ribs are a separate choice. Sheffield says clip relief, bead ribs, striations and pencil ribs do not affect the engineering of its mechanical seam panels. NTM sells these rib rollers as tooling options rather than separate profiles.
What the machines allow
Coverage also depends on the roll former. NTM lists these ranges.
| NTM machine | Coil width | Finished panel width | Example coverage range |
|---|---|---|---|
| SSQ3 MultiPro | 15″ to 30″ | 12″ to 24″ | SS150: 12″ to 24″ on SSQ machines |
| SSH MultiPro | 14″ to 24″ | 12″ to 20″ | SS150: 12″ to 20″ |
| SSR MultiPro Jr. | 15″ to 20″ | 12″ to 16″ | SS150: 11″ to 16″ |
So a 2-inch, 18-inch panel needs an SSQ-class machine, while SSH and SSR machines top out at narrower panels. Browse roof and wall panel roll formers, including the NTM SSH MultiPro, the NTM SSR MultiPro Jr. and the NTM SSQ II MultiPro.
Trim coil vs. panel coil
Panel coil is slit to the width your roll former needs, in panel gauges. NTM’s SSQ3 runs painted steel from 28 to 22 gauge and aluminum from .027 to .040 inch.
Trim coil is what you bend on a brake for flashing, wraps and trim. Retail aluminum trim coil is often lighter. Gibraltar, for example, lists its 24 inch by 50 foot trim coil at a nominal .019 inch. For roofing trim, bend from the same metal and finish as the panels when you can, so color and gloss match. Check your brake’s capacity in choosing a Van Mark brake.
Gutter coil has its own widths. NTM’s MACH II needs 11-3/4 to 12-3/8 inch coil for a 5-inch gutter and 15-inch coil for a 6-inch gutter. Check coil size against the machine too. NTM recommends no more than 1,000 lb on the MACH II reel and 400 lb on its cradle, with a 30-inch maximum coil diameter. For heavier panel coil, look at decoilers.
Wide coil can be cut down. Van Mark’s Trim-A-Slitter slits aluminum up to .040 inch and painted steel up to 24 gauge. Ask about coil slitting or see metal slitters.
How to figure linear feet of coil for a roof
Coil runs the length of each panel, so linear feet of coil equals the total length of all panels.
- Measure each plane. Note the eave length and the panel length from eave to ridge, plus the hem and overhang your panel details call for.
- Count panels. Divide the eave length in inches by the coverage, and round up.
- Add up the length. Multiply panels by panel length for each plane, then add the planes.
- Convert to weight. Multiply linear feet by pounds per foot from the gauge and weight chart.
- Add waste. Hips, valleys and cut-offs need extra. Sheffield’s multipliers do not include waste.
Worked example
Take a simple gable roof with two 40-foot eaves and 20-foot panels. Use a 1.5-inch mechanical panel at 16 inches of coverage, rolled from 20-inch, 24 gauge steel.
- Panels per side: 480 inches ÷ 16 = 30 panels.
- Linear feet: 2 sides × 30 panels × 20 feet = 1,200 linear feet of 20-inch coil.
- Check by area: 1,600 square feet of roof × 1.25 = 2,000 square feet of coil. That equals 1,200 feet × 20/12 feet of width.
- Weight: 1,200 feet × about 1.63 lb per foot ≈ 1,950 lb, before waste.
The coil for a roof calculator runs these steps for you.
Panels per coil
Turn coil weight into footage, then into panels. A 1,000 lb coil of 20-inch, 24 gauge steel holds about 614 linear feet. That is 30 full 20-foot panels, or one side of the example roof. Plan panel lengths so the leftover coil is useful for trim. The panels per coil calculator does the math.
Quick answers
Can I roll a wider panel from a wider coil?
The machine may allow it, but the engineering may not. Sheffield’s cut sheets allow heavier gauge and narrower panels without changing clip spacing. Ask the panel maker before going wider than the tested width.
Why is my coil order bigger than the roof area?
The seams use coil. A 16-inch panel from a 20-inch coil needs 1.25 square feet of coil for each square foot of roof, before waste.
Sources
Figures in this guide come from the documents below or are calculated from them. Specs and warranty terms change, so check the current version before you order.
- Sheffield Metals, SMI 1.0″ FF SnapLock cut sheet
- Sheffield Metals, SMI 1.0″ Mechanical Seam cut sheet
- Sheffield Metals, SMI 1.5″ SnapLock 450+ cut sheet
- Sheffield Metals, SMI 1.5″ SnapLock 550 cut sheet
- Sheffield Metals, SMI 1.5″ Mechanical Seam cut sheet
- Sheffield Metals, SMI 2.0″ Mechanical Seam cut sheet
- New Tech Machinery, FF100 1″ Snap-Lock With Slotted Flange profile
- New Tech Machinery, SS100 1″ Mechanical Seam profile
- New Tech Machinery, SS450 1.5″ Snap-Lock profile
- New Tech Machinery, SS150 1.5″ Mechanical Seam profile
- New Tech Machinery, SSQ200 2″ Mechanical Seam profile
- New Tech Machinery, SSQ3 MultiPro Roof and Wall Panel Machine
- New Tech Machinery, SSH MultiPro Roof Panel Machine
- New Tech Machinery, SSR MultiPro Jr. Roof Panel Machine
- New Tech Machinery, MACH II 5″/6″ Combo Gutter Machine
- Gibraltar Building Products, gauge of 24 in. x 50 ft. aluminum trim coil
- Van Mark, Trim-A-Slitter
Send your profile, coverage and panel cut list, and we will price the coil to match. See steel coil and aluminum coil for widths and finishes.