SettingsSettings for this calculationUS
The total roof area to be covered with the modified bitumen cap sheet.
Measure the full roof plane area to receive the torch-applied modified bitumen cap sheet.
Extra material to allow for granule embedment loss and heat damage at seams.
Torching the cap sheet embeds and displaces surface granules at overlaps and can scorch material at seams, so extra material beyond the bare roof area is commonly allowed for.
The net usable coverage area of a single cap sheet roll after overlaps.
Use the manufacturer's net coverage area per roll — a common 1 m × 10 m roll (about 3 ft 3 in × 33 ft) is 10 m² or 108 sq ft gross, and nets roughly 9.3 m² or 100 sq ft once overlaps are accounted for.
Cap sheet material needed
12 sheets
Scrap allowance varies with installer technique and seam density — this is a general estimating allowance, not a substitute for job-specific takeoff on complex roofs with many penetrations.
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Modified Bitumen Cap Sheet Scrap Factor Calculator: 12 sheets — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- Sheet count = ceil((roof area × (1 + scrap allowance)) ÷ sheet coverage area); torch-applied modified bitumen commonly requires an added scrap factor to account for granule embedment loss and heat damage at seams during application
Inputs used
- Roof Area
- 1080 sq ft
- Granule Loss Scrap Allowance (%)
- 8
- Sheet Coverage Area, Net of Overlap
- 100 sq ft
Confidence note: Scrap allowance varies with installer technique and seam density — this is a general estimating allowance, not a substitute for job-specific takeoff on complex roofs with many penetrations.
What this calculation does not cover
- Counts the CAP SHEET and nothing under it. A torch-applied roof is normally at least two plies - a mechanically fastened or self-adhered base sheet beneath the cap - and that base ply has its own roll coverage and its own laps, so it needs a second run through this sum. The scrap percentage entered above does not quietly contain it.
- Flashing is a perimeter quantity, not an area one. Base flashing at parapets, curbs, skylight kerbs and drain sumps is cut from separate rolls and measured by the running length of upstand, so two roofs with identical area and different detailing consume very different amounts of material. A percentage spread across the field never sees that difference.
Estimated cost — your price
This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.
Part of bigger jobs
This trade is one line of several job takeoffs. Run the whole job and every other trade comes back with it, off the same measurements.
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Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-06 · in the site-wide review of 2026-09-06 · v1.1.1
Regulatory standards & verification citations1
- Sheet count = ceil((roof area × (1 + scrap allowance)) ÷ sheet coverage area); torch-applied modified bitumen commonly requires an added scrap factor to account for granule embedment loss and heat damage at seams during application
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Your workspace
Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.
Tools and safety for this job
To lay a hot-applied bitumen membrane. Generic types, no brands, no prices.
Protection this work requires
- Torch work ignites dust and joists hours later: use a heat mat, keep an extinguisher to hand, and re-check the area an hour after the last flame.
- Most fatal falls on small jobs are from under three metres: use a tower or a ladder tied at the top, and never work off the top two rungs.
Lay a hot-applied bitumen membrane: This site does not publish a tool list for torch-applied roofing. A gas torch on a roof is hot work that starts fires in timber decks, insulation and eaves hours after the crew has gone; it is done by roofers trained for it, under the hot-work controls the insurer and the site set, with a fire watch after the torch goes out. Cold-applied and self-adhesive membranes remove the flame altogether.