Pricing and business
Labour time from roof area and daily output
- where
- roof area (m²)
- output per person per day (m²/day)
- number of roofers
- extra days for strip-out, deck, trims or curing
- working hours per day
Explain this equation
Gives a rough programme for a roofing job from the area, your daily output and the size of the gang. Use it for quoting labour and booking the scaffold.
P is how many square metres one roofer lays in a day on this system. With k roofers the team lays P × k per day, so the area divided by that is the laying time. X adds days that do not scale with area, such as stripping, decking, detailing or waiting for a cure. Multiplying by the hours per day gives crew hours; the calculator also multiplies by k for person-hours.
Time is work divided by rate of work, plus fixed tasks.
Sense check: 20 m² at 10 m² per person per day with two people is one day of laying, plus one extra day: 2 days, 16 crew hours, 32 person-hours.
Watch out: output on small, cut-up roofs is much lower than on open areas, and weather days are not included.
Estimates how long a flat roof job will take from the area, your crew’s daily output and the fixed time for preparation and details.
Enter your values to see the result.
Good to know
Output depends on the system, access, weather and how cut-up the roof is, so use your own records for similar work. Allow separately for strip-out, decking, upstands and trims, and for waits such as GRP cure time between coats (catalyst rate and temperature control it) or adhesive flash-off. Flat roofing is weather-dependent: build in a margin for lost days.
Common mistake
Pricing the field area only. On small roofs, upstands, outlets and edge trims can take as long as the main area.
Limits
Continuous working, steady output. Does not account for travel, access, scaffold time or weather.
Sources
Results are calculations from the published methods and figures shown, and depend on the data you enter. Follow the roof covering manufacturer’s fixing specification, BS 5534, BS 8000-6, BS 6229, the Lead Sheet Training Academy guidance and Building Regulations. Wind uplift and structural design need a competent designer.