Labor is usually the largest single line on a commercial roofing bid, and it is the line owners examine least. Material is easy to interrogate because it has a brand, a thickness and a warranty. Labor arrives as a number, and the instinct is to treat it as the contractor’s business rather than yours.
It is worth treating as yours, because labor is where the real differences between bids live. Two contractors quoting the same membrane at the same thickness on the same building can differ by a wide margin, and the gap is almost always a different view of how long the roof will take and what will be found once it is open.
The unit, and where it goes wrong
A square is one hundred square feet. Everything in the trade is priced in squares, which makes bids comparable as long as both bidders measured the same roof.
They often have not. Measured roof area is larger than the building footprint, because vertical surfaces are part of the work. Parapet walls get flashed. Curb sides get flashed. Equipment screens, level changes and stair bulkheads all add area, and all of that area is labor rather than easy field coverage.
So when two bids state different square counts for one building, start there. Ask each bidder what they measured and whether vertical surfaces are included. That one question frequently explains most of the difference, and it tells you which bidder actually went up on the roof.
Why labor dominates a reroof
On new construction the deck is clean, the access is open and nothing has to come off. On a reroof the sequence is inverted, and most of it happens before any new roofing is installed.
- Tear off. The existing roof is cut, lifted, carried down and taken away. More layers means more labor, and some older roofs are heavy.
- Deck inspection and repair. With the roof open, the deck is finally visible, and whatever is wrong with it is dealt with then.
- Insulation. Wet board comes out and new board goes in, often thicker than what came off because current energy code asks for more.
- Details. Every curb, pipe, drain, wall and corner is rebuilt by hand, one at a time.
- Field. Only now does the membrane roll out, which is the fast and cheap part of the whole job.
That ordering explains why a reroof price per square bears little relation to a new build figure. Comparing them tells an owner nothing useful about whether a price is fair.
Complexity costs more than area
A large, open, low parapet roof with four pipes on it is the cheapest surface in commercial roofing. The same square footage carrying forty penetrations, three level changes, a screen wall and a skylight array is a different job at a different rate, because almost none of it is field work.
| What the roof has | Effect on labor per square |
|---|---|
| Few penetrations, open field | Lowest |
| Many curbs, pipes and skylights | Rises sharply, each is hand work |
| Level changes and tall parapets | More flashing, more cutting, more waste |
| Small total area | Rises, because setup is a fixed cost |
| High building or poor access | Rises, material handling dominates |
| Occupied, with restricted hours | Rises, less completed per shift |
The practical step is to count your own penetrations before reading any bid. Then ask each bidder what count they worked from. The bidder whose number matches yours is the one whose price will still be the price in six weeks.
Access and the things that sit outside the roof
Getting material up and waste down is a real cost and an invisible one. A crane for a day, a lift for a week, or a crew carrying board up a stair all price differently, and the choice is dictated by the building rather than the roof.
Disposal is the other one. Tipping fees are a line item, and on a metal tear off the scrap value of the old roof should be credited back to you rather than quietly retained.
Where overruns actually come from
Not from the rates. From quantities nobody knew about when the rate was agreed. Three items account for most of it:
- Deck repair, discovered when the old roof comes off.
- Wet insulation, whose extent was never measured.
- Extra flashings, because the penetration count was an estimate.
All three are solved the same way, and it is the single most useful thing an owner can do with a roofing budget. Run a moisture survey before the bids go out, and ask for those three items as stated unit rates with quantity allowances rather than as exclusions. An exclusion means the number you were given was never the number. A rate plus an allowance tells you the scale of the risk and gives you arithmetic instead of an argument. Our page on fitting a reroof into a capital plan covers how that allowance should be carried.
Crew productivity, and what it is reasonable to expect
Behind every labor figure is an assumption about how much a crew completes in a day. That assumption is where experience shows up, and it is the part of a bid an owner can sanity check without being a roofer.
Ask how many crew will be on the roof, for how many days, and what each phase is expected to take. A contractor who has done the work can answer immediately: so many days to tear off, so many to insulate, so many for details, so many for the field. A contractor who cannot answer has not planned the job, and an unplanned job is where the schedule slips and the roof sits open through a storm.
The answer also lets you judge the price for yourself. Crew size multiplied by days gives you the labor content of the bid in a form you can compare across bidders, even without knowing anybody’s hourly rate. Where one bidder has allowed half the days of another on the same roof, one of them is wrong, and it is worth finding out which before you award rather than after.
Weather, and who carries the risk of it
An open roof is a liability until it is closed, and closing it each evening is labor. Crews build temporary seals at the end of a shift, and on a roof that is being torn off in stages, every stage is sealed and reopened.
That cost is in the bid as an assumption about the weather. A contractor working in a predictable dry season will assume less of it than one working into winter, and the same roof therefore prices differently in different months. It is also why the cheapest time to reroof is rarely the most convenient, and why a project pushed into a wet season should be repriced rather than squeezed.
What to ask for in writing
- Measured square count, and whether vertical surfaces are included.
- Penetration count used.
- Tear off: how many layers assumed, and disposal included or separate.
- Deck repair as a rate per square foot, with an allowance.
- Wet insulation replacement as a rate, with an allowance.
- New curb or pipe flashing as a rate each.
- Working hours assumed, and any premium time included.
Where to go next
If the decision in front of you is still whether to replace at all, recover against tear off is the cheaper question to answer first, because a recover removes most of the labor described above. If replacement is settled, what a commercial replacement involves sets out the sequence the labor is paying for.
Common questions
What is a roofing square?
A square is one hundred square feet of roof area, and it is the unit the whole trade prices in. Material quantities, crew productivity and labor rates are all quoted per square, so a bid expressed any other way is harder to compare against the market than it needs to be.
- One square equals one hundred square feet
- Material and labor are both quoted per square
- Area is measured on the roof, not from the footprint
- Parapets and curbs add area that the footprint misses
- Waste allowances are added on top of measured area
Measured roof area is almost always larger than the building footprint suggests, because vertical surfaces are part of the job. Parapet walls, curb sides and equipment screens all get flashed, and all of that is labor. When two bids state different square counts for one building, the first thing to establish is whether they measured the same surfaces, because that alone can account for the gap.
Why is labor usually more than material on a reroof?
Because a reroof is mostly handling rather than installing. The old roof has to come off, be carried down and taken away, the deck has to be checked and repaired, and every detail has to be rebuilt by hand before any new membrane goes down on open field.
- Tear off and disposal are labor before anything is installed
- Deck inspection and repair happen with the roof open
- Every curb, pipe and wall is flashed individually
- Material moves to the roof by crane, lift or by hand
- Weather stops work and open roofs must be made safe nightly
New construction reverses the ratio, because the deck is clean, access is open and nothing has to be removed. That is why a reroof cost per square on an occupied building bears little relation to a new build figure, and why quoting one against the other misleads an owner about whether a price is fair. Compare reroof prices only with other reroof prices on similar buildings.
What makes one roof cost more per square to install than another?
Complexity and access, in that order. A large open roof with few penetrations is the cheapest surface to cover. The same area broken up by curbs, skylights, walls, level changes and equipment costs considerably more, because every one of those is hand work.
- Penetration count: each one is measured and fabricated
- Level changes and parapets add flashing and cutting
- Building height decides how material reaches the roof
- Restricted access slows every delivery and every removal
- Occupied buildings limit working hours and noise
Small roofs also cost more per square than large ones, for the same reason a small concrete pour does. Setting up, moving material, establishing safety and demobilizing are largely fixed costs, and on a small roof they are spread across very few squares. An owner comparing a small roof's price per square against a warehouse figure is comparing two different economics, and the small roof will always look expensive by that measure without being overpriced.
Should I ask for labor and material to be separated in a bid?
It helps, but what helps more is asking for unit rates on the work most likely to change. Deck repair, insulation replacement and additional flashings are the items that grow once the roof is open, and a stated rate per unit turns a dispute into arithmetic.
- Ask for deck repair as a rate per square foot
- Ask for wet insulation replacement as a rate
- Ask what a new curb flashing costs each
- Ask whether the rate covers labor only or labor and material
- Ask what the allowance assumes, in quantity
A split between labor and material tells you how a contractor structures a bid, which is interesting. Unit rates tell you what the variations will cost, which is useful. The second question is the one that protects the budget, because the overruns on roofing projects come almost entirely from quantities discovered after the price was agreed rather than from the rates themselves.
Does hot work or an occupied building change the labor cost?
Yes, and often significantly. Torch applied systems need hot work permits and a fire watch that stays after the crew leaves. Occupied buildings restrict hours, noise, fumes and access, and each restriction reduces how much a crew can complete in a shift.
- Hot work permits and fire watch are chargeable time
- Odor and fume limits can rule out some adhesives
- Night and weekend work carries premium labor rates
- Tenant protection and dust control add setup time
- Interior protection is sometimes needed beneath the work
These constraints are worth raising before bids go out rather than discovering them through a variation. A hospital, a school or a food production building will all impose rules that change the system choice as well as the price, and a contractor who learns about them after award will reprice the job. Stating them in the invitation gets comparable bids back, and it stops the lowest bidder being simply the one who did not know what the building would ask of them.