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The Sheets a Roofing Takeoff Has to Read Besides the Roof Plan
Disclosure: Sharp Pencil sells commercial roofing takeoffs, so we have a stake in this topic. The example plan set below is made up for illustration. It is not a real job.
Read the roof plan, then check every sheet that changes a roofing quantity. Plumbing sheets show primary and overflow drains. Mechanical and electrical sheets show curbs, units and penetrations. Structural sheets show deck type and slope, which set fasteners and attachment. Elevations and wall sections show parapet and wall heights, which set flashing height. The spec book names the system and the details. Skip one and the takeoff misses lines.
Why isn't the roof plan enough for a roofing takeoff?
The roof plan shows areas, slopes, and what the architect chose to draw on the roof. The trades that put things through the roof draw them on their own sheets, and the architect's roof plan may lag behind those sheets.
A takeoff from the roof plan alone tends to get the squares roughly right and miss the counts and heights that drive flashing, labor and accessories. Drains, curbs, pipe and conduit penetrations, and parapet heights all live somewhere else in the set. When those sheets disagree with the roof plan, see what to do when the roof plan and the details disagree.
Which sheets matter, and what does each one add?
Firms number and title sheets differently, so work from the sheet index, not from a sheet number you expect to see. Check the index against what you actually received before you start.
| Sheet | What to pull for the takeoff | What gets missed without it |
|---|---|---|
| Architectural roof plan | Roof areas, slope arrows, crickets and saddles, drain and scupper locations as the architect drew them, roof hatches, walkway pads | Nothing; it is the starting point |
| Roof details and sections | Edge, coping, curb, drain, penetration and expansion joint details with their callouts | The actual flashing method and materials for each condition |
| Exterior elevations and wall sections | Parapet heights, wall heights at roof to wall transitions, scupper and downspout positions | Vertical membrane area and flashing height |
| Structural | Deck type and gauge, slope built into the structure versus tapered insulation, framed openings, new or existing deck | Fastener type, attachment method, and whether tapered insulation has to make all the slope |
| Plumbing | Roof drains, overflow (secondary) drains, vent stacks, gas piping to rooftop equipment | Drain count, overflow drains, pipe penetrations |
| Mechanical | Rooftop units, exhaust fans, curbs and rails, duct penetrations, equipment supports, and gas piping where the mechanical engineer draws it | Curb count and size, equipment rails, duct and pipe penetrations |
| Electrical | Conduit penetrations, rooftop disconnects, lightning protection, solar or roof mounted equipment if shown | Small penetrations and supports |
| Spec book (Division 07 roofing sections) | System, manufacturer, attachment, warranty, accessories | The system the quantities have to be converted into |
Why do drains have to come from the plumbing sheets?
The plumbing engineer sizes the storm drainage, so the plumbing sheets usually carry the drain schedule and the overflow drains. The architect's roof plan may show fewer drains, or primary drains only.
The code ties the two together. These citations are to the model 2021 code; check your local adoption.
- 2021 IBC Section 1502.1 says roof drainage design and installation comply with Section 1502, Section 1611, and the International Plumbing Code (IPC) Chapter 11.
- 2021 IPC Section 1108.1 requires secondary (emergency overflow) roof drains or scuppers where the roof perimeter construction extends above the roof in a way that would trap water if the primary drains allow buildup.
- 2021 IPC Section 1108.2 requires the secondary system to have a discharge end point separate from the primary system.
So overflow drains are their own count. Each one is another drain flashing and another drain location in the tapered layout.
On a reroof, 2021 IBC Section 1512.1 lets a recover or replacement skip new secondary drainage where the roof provides positive roof drainage, and existing required secondary drainage cannot simply be removed. Jurisdictions amend Chapter 15 (Massachusetts, for example, swaps the plumbing code reference for its own regulations), so check the local edition and amendments.
Where overflow is by scupper, 2021 IPC Section 1108.3 sets a minimum 4 inch opening height. The scupper and its conductor head or downspout show on the elevations, not always on the roof plan.
What do the mechanical and electrical sheets add?
They add curbs, rails and equipment supports for each rooftop unit and fan, and every duct, pipe and conduit that comes through the deck. Pull these from them:
- Curb count and perimeter, for curb flashing.
- Penetration count by type: pipe boots, pitch pans, or whatever the details call for. Gas piping to rooftop units comes from the plumbing or mechanical sheets, depending on which engineer drew it. Conduit comes from the electrical sheets.
- Equipment that limits where the crew can work.
Flashing height has a manufacturer minimum. As one example, the IKO Innovi TPO installation manual says all flashings must extend a minimum of 8 inches above the roof level. Follow the specified manufacturer's rule on your job. If a curb on the mechanical detail looks too short for that rule, put it on the RFI list instead of assuming.
What does the structural set change on the takeoff?
Deck type decides fasteners and attachment. As one example, the WeatherBond TPO mechanically attached and fully adhered system specification (January 2024) lists different fasteners for steel and structural concrete decks and has separate fastening tables for plywood and OSB. It says its mechanically attached system is not acceptable on steel decks lighter than 22 gauge unless the deck is used with lightweight concrete and each HPWX fastener achieves at least 360 lb pullout. Same roof area, different fastener line.
The structural set also shows whether slope is built into the structure. If the structure is dead flat, the tapered layout has to make all the slope, which changes insulation volume.
On a reroof, the structural set may not show the condition of the existing deck. That is a site question or an RFI, not a takeoff assumption.
Why do elevations and wall sections matter?
Parapet and wall heights at roof transitions set vertical membrane area and termination height. For the math, see measuring parapet membrane wrap.
Where a roof meets a taller wall, the elevation shows how high the flashing has to go and where the counterflashing or wall system takes over. Elevations also show scupper, conductor head and downspout positions.
Does a roofing takeoff need the spec book?
Yes. The spec names the system, manufacturer, attachment and warranty, and those turn measured quantities into material lines. Without it you have areas and counts but no way to convert them into what gets ordered. If the set covers roofs with more than one system, the spec tells you which system goes where. Warranty terms also add quantities; see what warranty requirements add.
Some costs, like hoisting and fall protection, never show up as a measured quantity at all. See costs that never show up as a measured quantity.
Example: what each sheet changes (an example, not a real job)
This plan set is made up for the example: a one story building with a low-slope single-ply roof, parapets on three sides and an open edge on the fourth.
| Item | Roof plan only | Full set | Takeoff change |
|---|---|---|---|
| Roof drains | 6 drains | Plumbing: 6 primary plus 6 overflow drains | 12 drain flashings instead of 6, and 12 drain locations in the tapered layout instead of 6 |
| Curbs | 4 rooftop units | Mechanical: 4 units plus 3 exhaust fan curbs | 7 curbs to flash, not 4 |
| Penetrations | None shown | Plumbing: 8 vent stack and gas pipe penetrations. Mechanical: 1 duct penetration. Electrical: 5 conduit penetrations | 14 penetration details that were not on the roof plan |
| Parapet height | Parapet line, no height | Elevations: height shown | Vertical membrane goes from unknown to measured |
| Deck | Not stated | Structural: steel deck, gauge noted | Fastener type can be set |
Before you call the takeoff done
- Sheet index checked against what you received.
- Drains counted on plumbing, including overflow.
- Curbs and fans counted on mechanical.
- Penetrations counted across plumbing, mechanical and electrical.
- Deck type confirmed on structural.
- Parapet and wall heights taken from elevations and sections.
- System and manufacturer taken from the spec.
- Every gap written up as a question for the GC.
Send your first job free
Your first takeoff is free, one per contractor, on a job you're bidding or quoting. Upload the plan set and you'll get back quantities you can check against the sheets.
Usually within one business day. Delivered within 48 hours*
*Clock starts once any questions we send you are answered.
FAQ
Where are roof drains shown on construction drawings?
Check the plumbing sheets first. The plumbing engineer sizes the storm drainage, so the plumbing plans and drain schedule usually show every primary and overflow drain. The architectural roof plan may show only some of them.
Do overflow drains count separately on a roofing takeoff?
Yes. Where the model 2021 code requires secondary drainage, each overflow drain is its own drain location, with its own drain flashing and its own spot in the tapered layout. Check your local adoption.
How do I find the roof deck type on the plans?
Look at the structural sheets: the framing plans, general notes and deck schedule usually name the deck type and, for steel, the gauge. If the structural set does not say, put it on the RFI list rather than assume it.
Can I do a roofing takeoff without the spec book?
You can measure areas and count items without it, but you cannot finish the takeoff. The spec names the system, manufacturer, attachment and warranty, and those turn measured quantities into material lines.
What sheets do you need to send for a Sharp Pencil takeoff?
Send the full set: architectural, structural, mechanical, plumbing, and the spec book if you have it. Every quantity in the takeoff workbook cites the sheet it came from.
Why send your takeoffs to Sharp Pencil
If takeoffs are piling up and you're passing on jobs because nobody has the hours, here's what you get when you send them to us.
- Usually within one business day. Delivered within 48 hours*. A takeoff stuck in a week-long queue does you no good when the bid is due sooner.
- Every page gets read. Architectural, structural, mechanical, plumbing, and the spec book if you have it.
- Every quantity names its sheet. Each line cites the sheet it came from, so you can check it against the drawings.
- No silent blanks. If the drawings can't settle a line, you get a written reason for it. Anything you haven't priced prints as UNPRICED with the quantity shown.
- Questions instead of guesses. If the set leaves something open, like a drain count that differs between the roof plan and the plumbing sheets, it goes on the open questions (RFI) list that ships with your takeoff.
- A material order list. Included with your takeoff whenever the set supports one.
- Checked before it goes out. Every paid takeoff, before delivery.
- Your plans stay yours. Used for your takeoff, never shared, and deleted whenever you ask. See what happens to your plans.
- Your first takeoff free. Your first takeoff is free, one per contractor, on a job you're bidding or quoting. After that, $395 per new set of drawings, or monthly plans: Shop 12 at $2,750/mo, Shop 25 at $5,500/mo, and Shop 60 at $11,000/mo. See what a takeoff costs and how it works.
We work on commercial low-slope roofing. Residential isn't our focus today, but ask if you have a job in mind. See our commercial roofing takeoff services.
Upload your plans · See full pricing and plan terms · Or email [email protected]
*Clock starts once any questions we send you are answered.
The Sharp Pencil team
Sources
- International Code Council, 2021 International Plumbing Code, Chapter 11 Storm Drainage, Sections 1108.1, 1108.2, 1108.3 (model code). Adopted text read via Texas IPC 2021 on UpCodes: https://up.codes/viewer/texas/ipc-2021/chapter/11/storm-drainage
- International Code Council, 2021 International Building Code, Chapter 15, Sections 1502.1, 1512.1 (model code). Adopted 2021 Chapter 15 text read in the City of Seattle 2021 Seattle Building Code, Chapter 15: https://www.seattle.gov/documents/Departments/SDCI/Codes/SeattleBuildingCode/2021SBCChapter15.pdf
- Massachusetts 780 CMR, 10th edition, Chapter 15 amendments: https://www.mass.gov/doc/10th-edition-chapter-15-roof-assemblies-and-rooftop-structures/download
- IKO, Innovi TPO single-ply installation manual: https://www.iko.com/comm/wp-content/uploads/sites/7/2024/02/iko-innovitpo-installation-manual-single-ply-en.pdf
- WeatherBond, TPO Mechanically Attached and Fully Adhered Roofing Systems specification, January 2024: https://www.weatherbondroofing.com/wp-content/uploads/WeatherBond-TPO-for-Web-January-2024-.pdf