To do a roofing takeoff from a PDF, set the scale on the roof plan, trace each roof plane as an area, measure the edges as linear feet, count the penetrations, then apply pitch and waste. Everything else is checking. This guide walks through that sequence the way a roofing estimator would run it on a real plan set, with numbers you can test against your own jobs.
TL;DR
- Calibrate the scale against a known dimension on every sheet, never trust the title block alone.
- Take off areas (planes), linear feet (eaves, ridges, hips, valleys, rakes, flashing) and counts (vents, drains, curbs) as three separate passes.
- Pitched roofs need a pitch multiplier on plan area. Flat and low-slope roofs usually don't, but tapered insulation does need zone-by-zone work.
- There is no single waste number. Simple gable roofs run low, cut-up roofs run much higher, so set waste per roof, not per company.
- Check the total against a second method before you price. A five-minute sanity check beats a lost bid.
Table of Contents
- What a roofing takeoff actually has to produce
- Before you measure: read the PDF properly
- Step 1: Take off the roof areas
- Step 2: Take off the linear feet
- Step 3: Count the penetrations and accessories
- Step 4: Convert to material quantities
- A worked example
- Common mistakes that cost roofing bids
- Which tool setup works for a roofing sub
- Our view: the takeoff is where you decide if the job makes money
- Run your roofing takeoffs inside Subascent
- FAQ
- Sources
What a roofing takeoff actually has to produce
A takeoff is not the bid. It is the list of quantities the bid is built from. For a roofing sub, that list has three kinds of numbers:
- Areas: each roof plane, deck area, insulation zones, underlayment coverage. Reported in square feet, then converted to squares (100 square feet each).
- Linear feet: eaves, rakes, ridges, hips, valleys, step flashing, wall flashing, drip edge, parapet and coping.
- Counts: pipe boots, vents, roof drains, scuppers, curbs, skylights, hatches.
Most errors come from skipping one of those passes, not from bad math. Estimators who only trace areas end up pricing shingles or membrane correctly and then eating the cost of flashing and edge metal.
The same three-pass logic applies in every trade. If you want the general version, our guide on PDF plan takeoff for trade subs covers the workflow from file setup to audit.
Before you measure: read the PDF properly
Spend ten minutes here and you save an hour later.
Find every sheet that touches the roof. The roof plan is the obvious one. Also pull the wall sections, details, elevations, the mechanical plan (curbs and roof-top units), and the specification section for roofing. The roof plan shows the shape. The details tell you what you're actually building.
Check the scale on each sheet. Plan sets get printed, scanned and resized. A sheet labeled 1/8" = 1'-0" can be off if the PDF was exported at a different page size. Find a long dimension string on the sheet, measure it with your takeoff tool, and compare. If the two disagree, calibrate to the written dimension. We wrote up a common trap in scaling PDF drawings locally: scaling one viewport and then measuring in another is how quantities get doubled or halved.
Note the pitch. Pitched roofs show slope as a rise over 12 inches of run, like 6:12. The plan view only shows the flat projection, so the pitch is what turns plan area into real surface area.
Read the spec for the system. Shingle, TPO, modified bitumen, standing seam metal and built-up roofing all take off differently. The spec also tells you the underlayment, the number of layers, the insulation thickness and the edge metal. Miss a second layer of insulation and you've missed thousands of dollars.
Step 1: Take off the roof areas
Trace each roof plane separately. Don't trace the whole footprint as one polygon, even on a simple roof. Separate planes let you apply different pitches, find mistakes quickly and reuse the numbers if the GC changes the design.
Label each area clearly: "Main roof north," "Garage," "Dormer 2." When someone opens the file six months later for a change order, they should be able to follow it.
Pitched roofs: apply the pitch multiplier
The plan shows the horizontal footprint. The actual roof surface is bigger. The multiplier is the square root of (rise squared plus run squared) divided by run, as this roofing calculator explains, which gives about 1.118 for a 6:12 pitch.
Run the same formula for other common pitches and you get:
| Pitch | Multiplier |
|---|---|
| 4:12 | 1.054 |
| 6:12 | 1.118 |
| 8:12 | 1.202 |
| 10:12 | 1.302 |
| 12:12 | 1.414 |
The multiplier works for a plain gable or hip plane. Eaves overhang is another matter: a plan often shows the walls, not the overhang, so check whether the traced line includes the eave or if you need to add it.
Flat and low-slope roofs
On a flat roof, the plan area is close to the surface area, so no multiplier applies. The catch is what sits on top of it. Trace the deck area, then deduct or separately count curbs and equipment pads. Wrap-up at parapets goes in as linear feet times height, not as area on the plan.
If the spec calls for tapered insulation, trace each thickness zone as its own area. Pricing the whole roof at an average thickness is how you underbid tapered systems.
Step 2: Take off the linear feet
Switch to the linear tool and make a pass for each edge type. Use a different color for each so the markup is readable on the PDF.
- Eaves: drip edge, starter strip, ice and water shield at the edge.
- Rakes: drip edge or rake metal.
- Ridges and hips: ridge cap, ridge vent.
- Valleys: valley metal or woven shingles, plus underlayment.
- Walls and curbs: step flashing, counterflashing, base flashing.
- Parapets and terminations: coping, termination bar, edge metal.
Hips, valleys and ridges run along the slope, so on a pitched roof their true lengths are longer than the plan shows. A hip or valley on a 6:12 roof with equal-pitch planes is longer than its plan length by a larger factor than the plane multiplier, because it runs diagonally. Many estimators calculate these from the plan length and pitch, or take them from detail sheets. Whatever you do, do it the same way every time and write it down.
For a sense of how many edge categories a finished measurement can carry, look at a typical manufacturer measurement report. A sample residential report from GAF lists eaves, hips, rakes, ridges, valleys, flashing, step flashing and drip edge as separate lines. That's a good template for your own pass list, and your takeoff should be able to produce the same breakdown from the PDF.
Step 3: Count the penetrations and accessories
Counts are the quickest part and the easiest to botch, because they hide in different sheets.
- Plumbing vents and pipe boots: from the plumbing plans or the roof plan.
- Exhaust fans, gooseneck vents, intake vents: from the mechanical plan.
- Roof drains, overflow drains, scuppers: from the plumbing and roof plans.
- Curbs, hatches, skylights, equipment rails: from the roof plan and mechanical plan.
Put a marker on each item as you count it. Then filter by marker type and check the total against the schedule on the drawings. If the mechanical schedule lists eight rooftop units and you counted six curbs, stop and find out why. Our walkthrough on counting items from a PDF shows how to set up counts so they can be audited later.
Step 4: Convert to material quantities
Now you turn measurements into things you order.
For asphalt shingle work, the basic conversion is squares. Total area divided by 100 gives squares, then squares times bundles per square gives bundles. Standard three-tab and architectural shingles are commonly packaged at three bundles per square, but check the product data sheet for the exact coverage, since some products differ.
Other roofing materials that sit on top of the shingles are listed in this manufacturer's guide to estimating roofing required: underlayment, starter strips, drip edge, valley materials and ridge cap. Use it as a checklist for what a typical asphalt job needs beyond the field shingles.
For membrane roofs, the conversion is roll coverage: roll width, less overlap, against your area. For metal, it's panel width and length by run, plus trim by the foot.
Waste: pick it per roof
Somebody will tell you there's a standard 25% rule. There isn't one. Industry guidance for asphalt roofing, such as the residential asphalt roofing manual from the Asphalt Roofing Manufacturers Association, treats waste as dependent on the roof's complexity. As a working guide, simple gable roofs sit in the low single digits to about 10%, and cut-up roofs with dormers, valleys, hips and many penetrations run 15 to 20% or more.
Set waste by looking at the roof, then store the number on the takeoff so the reviewer can see it. Wasted material is a cost. Wasted time arguing about it later is too.
A worked example
Take a small commercial building with a pitched section and a flat section.
Pitched section: plan area traced at 3,800 sq ft, 6:12 pitch.
- 3,800 × 1.118 = 4,248 sq ft of surface
- Add 10% waste: 4,248 × 1.10 = 4,673 sq ft
- Squares: 46.7, so order 47 squares
- At three bundles a square: 141 bundles
Flat section: deck area traced at 2,400 sq ft, with two curbs and three drains.
- No pitch multiplier
- Membrane area is 2,400 sq ft plus parapet wrap-up, which is linear feet times height
- Deduct nothing for small curbs, but add their flashing as counts
The check: the combined plan area is 6,200 sq ft. Surface area is higher than that because of the pitch. If your final pitched number came out below 3,800, something is wrong. This kind of reasonableness test catches wrong scale and doubled traces quickly.
A second check: compare your total to the building footprint on the civil or architectural site plan. If the roof plan and the footprint disagree by more than the overhang, one of them is mis-scaled.
Common mistakes that cost roofing bids
- Measuring from an unscaled PDF. Scanned sets drift. Calibrate every sheet.
- Tracing the building, not the roof. Overhangs, canopies and covered walkways belong on the roof takeoff but not in the wall outline.
- Forgetting the pitch on additions. Each section can have its own pitch.
- One waste number for every job. See above.
- Skipping the detail sheets. The plan shows the shape. The details tell you if you need two layers of insulation, a cover board or a specific edge metal.
- Not saving the markup. When the GC revises the set, you need to compare and update, not start over.
Also keep a flexible mind. Some estimators find a linear takeoff of wall lines from floor plans more reliable than an area takeoff when the roof plan is thin on detail. Use the method that matches what the PDF actually gives you.
Which tool setup works for a roofing sub
You don't need anything exotic. A usable setup does these things:
- Calibrates scale per sheet and stores it.
- Handles polygon areas, polylines and counts on the same markup layer.
- Applies a pitch factor to areas without a separate calculator.
- Lets you group by color and label, then export to your estimate.
- Keeps the markup so a revised plan set can be compared.
There are three broad types of tool. Satellite measurement services work from an address and suit residential reroofs, but they can't read a plan set for a building that hasn't been built. Roofing-specific estimating packages suit companies that only do roofing. General PDF takeoff tools that connect to your estimating and job costing work for subs who bid from plans against GCs and want the quantity to flow into the estimate and then the job budget. Pick the type that matches how your bids actually arrive.
If you're a sub in other trades as well, the same discipline carries over: see how it works for area takeoffs in general, or compare the same problem in flooring and drywall.
Our view: the takeoff is where you decide if the job makes money
We've watched a lot of trade bids go wrong, and it's rarely at the pricing step. It's at the quantity step, when somebody traced the roof in a hurry on bid day, with a due date in four hours and three other invitations in the inbox.
We think a roofing takeoff should do two things beyond giving you a number. First, it should be repeatable. Someone else in the office should be able to open the file and see what you traced and why. Second, it should carry forward. The quantity you bid should become the budget you track the job against. If your takeoff lives in a PDF on one estimator's laptop and your budget lives in a spreadsheet, you'll never know whether the 47 squares you bid were 47 squares you installed.
That is the reason we built our takeoff to sit inside the same system as bid tracking, estimating and job costing. It's built for specialty trade subs, not for GCs, and a roofer's day looks different from a GC's.
— Dave
Run your roofing takeoffs inside Subascent
Subascent is job and bid management software for specialty trade subcontractors, roofing included. PDF takeoff is available as an add-on, so your areas, linear feet and counts sit next to your bid tracking, estimates, submittals and daily reports, with QuickBooks sync for the money side. If you want your takeoff to feed the estimate instead of a spreadsheet, take a look at Subascent.
FAQ
How do I do a roof takeoff from a PDF?
Calibrate the scale on the roof plan, trace each roof plane as an area, and apply the pitch multiplier if the roof is sloped. Then measure edges as linear feet and count penetrations. Finish by adding waste and checking the total against a second method.
What is the 25% rule in roofing?
There is no universal 25% rule. Waste depends on the roof: simple gables run low, and complex roofs with many dormers, hips and valleys run 15 to 20% or more, per industry guidance. Set the figure per roof and record it on the takeoff.
Do I need a pitch multiplier on a flat roof?
No. Plan area is close to the surface area on a flat roof. You still need to add parapet wrap-up, flashing at curbs, and separate zones for tapered insulation.
Can I take off a roof from a PDF without special software?
Yes, with a PDF viewer that measures and a scale you've checked. It gets slow with revisions and many sheets, and quantities are hard to hand off to an estimate. A takeoff tool that stores calibrations, markups and labels saves the rework.
Sources
- Roofing calculator: pitch multiplier, waste and squares formulas
- Residential Asphalt Roofing Manual, Asphalt Roofing Manufacturers Association
- Estimating How Much Roofing Is Required, IKO