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Modified Bitumen and Built-Up Roof Takeoffs: Ply by Ply From the Plan Set

By The Sharp Pencil team

Disclosure: Sharp Pencil sells commercial roofing takeoffs, so we have a stake in this topic.

Take off a mod bit or built-up roof one layer at a time. Start with the spec's ply count and list each layer in squares: base sheet, interply or ply felts, then cap sheet or flood coat and gravel. Add primer where the substrate needs it. Add the bonding material the application method calls for, in pounds of hot asphalt or gallons of cold adhesive. And count the flashing plies at walls, curbs, and edges as their own lines.

What does a mod bit or BUR takeoff have to list?

Every layer the spec names, each in its own unit, plus the bonding material between layers and the flashing plies. A multi-ply asphalt roof hides quantities inside the ply count. Roll it all into one "membrane, SQ" line and that's where the bid comes up short.

Table 1. Multi-ply asphalt roof takeoff lines
LineUnitWhere it comes from in the setNote
Deck typeNoteStructural sheetsDecides primer and base sheet attachment
Vapor retarder (if specified)SFDivision 07 roofing sectionOften missed when it sits in a general note
Insulation, by layer and thicknessSF per layerRoof plan, sections, specOne line per layer
Cover boardSFSpec, sectionsType and thickness from the spec
Tapered insulation and cricketsFlagRoof plan, tapered layoutFlag for a tapered quote
Base sheetSQDivision 07 section (07 52 00 for mod bit, 07 51 00 for BUR; confirm on the set)Attachment method from the spec
Ply sheets or interply feltsSQ times ply countDivision 07 sectionThe line that drops when "4 ply" becomes one line
Cap sheet, or flood coat and aggregateSQ; aggregate in lb or tons per specDivision 07 sectionGravel surfaced BUR carries both flood coat and aggregate
PrimergalSpec or manufacturerOnly where called for, for example concrete decks
Bonding materiallb of hot asphalt or gal of cold adhesive, by layerDivision 07 sectionSee Table 2
Base flashing plies at walls and parapetsLF with heightElevations, sections, detailsHeight drives material, not just length
Curb and penetration flashingsEA with sizeMechanical sheets, detailsSize each curb
Edge metal and stripping pliesLF by profileDetailsStripping plies are a separate line
Drains and sumpsEAPlumbing sheetsCheck against the roof plan
Walkway padsLF or SFRoof plan, specOften only in the spec
Coating (smooth cap with a specified coating)galDivision 07 sectionRate from the manufacturer

How do you turn a ply count into rolls?

Take the roof area in squares, multiply by how many layers of that sheet go down, and divide by the roll's stated coverage. Then add laps and waste.

It helps to know the sheet standards by number when you're reading a spec: SBS sheets fall under ASTM D6162, D6163, and D6164, APP sheets under D6222, D6223, and D6509, and foil surfaced SBS under D6298 (Professional Roofing, Specifying modified bitumen sheet products, January 2019).

Torch, hot mopped, or cold applied: what changes on the takeoff?

The application method is what adds the bonding material lines. The sheets can be nearly the same. What holds them together isn't.

Table 2. Application method and what it adds
Method What the takeoff adds Where to confirm
Hot mopped (BUR, and mop grade mod bit base sheets) Asphalt in pounds per ply; asphalt type; kettle or tanker and fuel; flood coat at the spec's rate Division 07 section; NRCA quality control guidelines
Cold applied Adhesive in gallons per layer; lap cement or lap adhesive as its own line Manufacturer spec; ARMA cold adhesive bulletin
Torch applied (APP and torch grade SBS) No field adhesive; flag torch-safe details at combustible substrates and wood nailers, and any spec fire watch requirement Spec and manufacturer details
Self adhered Primer per manufacturer Manufacturer data sheet

Hot mopped. Asphalt applied within 25°F of its equiviscous temperature (EVT) gives a nominal 23 to 25 pounds per ply per 100 square feet, and JM accepts a 25 percent deviation from the listed quantity (JM built-up roofing application guide). Specs often name a target: a United Asphalts BUR guide specification (Section 07510) calls for 25 pounds, plus or minus 20 percent, per 100 square feet (United Asphalts guide spec). The asphalt type (ASTM D312 Type I to IV) follows slope, and that same guide spec requires Type IV above 1/2 inch per foot. ARMA's technical bulletin on BUR asphalt covers the D312 types and EVT.

Cold applied. ARMA gives 1.5 to 2.0 gallons per 100 square feet for interply layers, higher for the first layer over porous substrates, and notes about 1.0 more gallon per 100 square feet over absorptive substrates. JM's SBS and APP specifications give a nominal 1.5 gallons per 100 square feet over nonporous substrates.

Torch applied. The takeoff carries the details, not the safety program: torch-safe details where the substrate or nailers are combustible, and any fire watch the spec requires. GAF notes that APP sheets are typically installed over a BUR base sheet or thermal barrier because many substrates can't be torched directly (GAF asphaltic systems).

Which sheets settle each line besides the roof plan?

When the sheets disagree or say nothing, that's an RFI. More on turning gaps into RFIs.

What usually goes on the RFI list for mod bit and BUR?

Worked example (an example, not a real job)

Assumptions: 20,000 SF roof (200 SQ), concrete deck, two ply cold applied SBS (base sheet plus granulated cap), insulation and cover board already counted, 1 SQ rolls for both sheets, waste left as a stated variable.

If the roof sits next to another system, see mixed-system roof takeoffs.

FAQ

How many rolls of modified bitumen do I need per square?

It depends on the product's printed coverage. Many modified bitumen base and cap sheets are 1 SQ per roll, so you need about one roll per square per layer, plus laps and waste.

How much hot asphalt does a BUR take per ply?

Asphalt applied within its EVT range gives a nominal 23 to 25 pounds per ply per 100 square feet, per JM's BUR application guide. One BUR guide spec calls for 25 pounds, plus or minus 20 percent, per 100 square feet.

How much cold adhesive per square for mod bit?

ARMA gives 1.5 to 2.0 gallons per 100 square feet for interply layers, with more over porous substrates.

Is a mod bit takeoff different from a TPO takeoff?

Yes. It has more layers, bonding material by layer, and flashing plies as separate lines. For single ply, see how to price a TPO roof.

Can Sharp Pencil take off a mod bit or BUR plan set?

Yes. You get every layer, ply, primer, bonding material, and flashing ply as its own line in your takeoff workbook, with the source sheet named on every quantity and open items written up as drafted RFIs.

Why send your takeoffs to Sharp Pencil

A takeoff backlog hurts most on the jobs you pass on because nobody has the hours. Here's how we handle the usual headaches.

Our focus is commercial low-slope roofing. Residential is not our focus today, but ask if you have a job in mind. See our commercial roofing takeoff services.

Send us a live bid · See full pricing and plan terms · Or email [email protected]

*Clock starts once any questions we send you are answered.

The Sharp Pencil team

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