Units of measure for roofing
Each piece of roofing work has its own unit, and keeping them apart is what makes the estimate checkable. These are the units estimators use and how each is measured.
| Item | Unit | How it's measured |
|---|---|---|
| Roof surface | SQ (100 SF) | Plan area × pitch factor on sloped roofs; plan area on low-slope roofs. |
| Shingles | bundles | Squares with waste × 3 bundles per square (tool default). |
| Underlayment | rolls | Roof SF plus 10% laps ÷ roll coverage. |
| Ridge, hip, eave, rake | LF | Measured on plan (rakes corrected for slope) for starter, ridge cap and drip edge. |
| Membrane, insulation, cover board | SQ | Low-slope field area, plus base flashing up walls and curbs. |
| Penetrations and curbs | each | Counted from the roof plan for flashing. |
How estimators take off roofing
- Measure each roof plane. Take plan dimensions including overhangs for each plane or roof area, and note its pitch.
- Correct for pitch. Multiply plan area by the pitch factor, √(rise² + 12²) ÷ 12. A 6/12 roof is 1.118 times its plan area.
- Take off edges and details. Eaves, rakes, ridges, hips, valleys, walls and penetrations drive starter, ridge cap, flashing and edge metal.
- Add waste and convert. Add 10% waste (tool default; more on cut-up roofs), then convert squares to bundles, rolls and pieces.
- Price labor and equipment. Use squares per crew-day for the system and add hoisting, tear-off, disposal and safety equipment.
Waste factors and order quantities
Waste covers cut-offs, breakage, laps and spillage, and it's added to the net quantity before rounding up to what the supplier sells. Figures marked as tool defaults are the same ones the Trade Takeoff Worksheets start with, and you can edit them there.
| Item | Factor | Notes |
|---|---|---|
| Shingles and membrane | 10% | Tool default; hips, valleys and dormers push it higher. |
| Underlayment laps | 10% | Tool default. |
| Ice and water shield | 3 ft up from eaves | Tool default; follow local code. |
Crew production rates
Labor is quantity divided by production. These rates are per 8-hour crew-day for commercial work, from the same library as the crew-day production estimator: typical mid-range planning values with a low-to-high range, not a promise of output. Crew skill, layout, access and weather move them, and your own crews' records beat any library.
| Activity | Crew | Low | Typical | High | Labor |
|---|---|---|---|---|---|
| TPO membrane, mechanically attached, with insulation | 5 roofers | 25 | 35 SQ | 45 | 1.14 hrs per SQ |
| Architectural asphalt shingles | 4 roofers | 18 | 25 SQ | 32 | 1.28 hrs per SQ |
- TPO membrane, mechanically attached, with insulation 25 to 45 SQ, typical 35
- Architectural asphalt shingles 18 to 32 SQ, typical 25
Worked example: a 40,000 SF (400 square) TPO roof
The activity is tpo membrane, mechanically attached, with insulation, with a crew of 5 roofers at the typical rate of 35 SQ per crew-day:
- Crew-days: 400 SQ ÷ 35 = 11.4 crew-days.
- Labor hours: 11.4 crew-days × 5 workers × 8 hours = 457 hours.
- Range: 8.9 crew-days at the high rate to 16 at the low rate, a spread of 7.1 crew-days on the same quantity.
- Equipment: Material hoist or telehandler, about 11.4 equipment-days.
Multiply the labor hours by your burdened hourly cost to price the labor. The spread between the low and high rate is why production is the assumption to check first on a roofing bid: the same takeoff can carry very different labor. Run your own quantities in the crew-day production estimator, and get the burdened rate from the labor burden calculator.
What drives the cost
- Tear-off. Removing existing layers, disposal and deck repair are often the biggest unknowns.
- Pitch and height. Steep and tall roofs need more safety equipment and cut production.
- Details. Penetrations, curbs, walls and complex edges take more time than field membrane.
- Warranty. Longer manufacturer warranties require specific systems and inspections.
Common exclusions and clarifications
A roofing price is only as good as the scope it describes. These exclusions come from our scope library for roofing (CSI 07 50 00); list the ones that apply so the GC levels your number fairly.
- Tear-off of more than one existing layer, or replacement of rotted decking beyond the allowance.
- Structural deck repair.
- Roof hatches, curbs and equipment supports furnished by others.
- Flashing of penetrations installed after the roof is complete.
- Roof walkway pads unless listed as included.
- Lightning protection.
Clarifications that often go with them:
- Flashing of penetrations installed before the roof; later penetrations flashed at time and material.
- One layer of existing roofing removed where tear-off is included.
Pick, edit and export these in the scope inclusions and exclusions library, or load them straight into a proposal with the bid proposal builder.
Free tools for roofing estimating
- Trade takeoff worksheets: measure roofing areas and get order quantities with the same waste factors, then download an Excel takeoff.
- Crew-day production estimator: turn roofing quantities into crew-days, duration and labor hours with the rates on this page.
- Labor burden calculator: find the true cost of a crew hour, with taxes, insurance and benefits.
- Scope inclusions and exclusions library: pick proposal-ready roofing exclusions and clarifications.
- Bid proposal builder: send a branded roofing proposal with the scope language loaded.
- Bond cost estimator: price payment and performance bond premiums on bonded work.