This calculator vs. a flat $650 per square special
"$650 a square" is not a price for a flat roof — it is a price for one specific roof, usually a small recover, quietly applied to every roof that calls for a quote.
What a flat per-square special is
A flat per-square number is the fastest thing a company can put on an ad or a postcard: one rate, times the plan squares, read back as a total. It is also the unit homeowners and property managers already compare between competing bids.
The rate was set for one job — commonly a small, one-story recover over an existing membrane, with no tear-off, no wet insulation, little or no parapet, and few penetrations — and then quoted to the next caller, whether or not that roof shares any of those.
What this calculator does instead
This page keeps no account and sends nothing to a server. You enter the membrane, scope, slope, stories, plan length and width, parapet, drains, HVAC curbs, walk pads, and polyiso layers, plus your own wage, payroll burden, membrane and insulation cost, dumpster, mobilization, permit, overhead, and target margin. It turns that into membrane squares after waste, tear-off and insulation squares, crew hours by task, and a price — for this roof, not a rate carried over from the last one.
| What a flat per-square special does | What this calculator does instead |
|---|---|
| Charges the same rate for a membrane recover and a full tear-off of the identical plan squares, even though tear-off is its own labor and dumpster line the recover never had. | Prices recover, tear-off, and tear-off-plus-insulation as their own scope, with tear-off hours, dumpster cost, and insulation hours and material priced separately. |
| Has no line for parapet flashing — a flat roof with no walls and one with 80 lf of parapet detail get the same rate. | Prices parapet hours and material by the lineal foot, and adds extra membrane waste for parapet flashing on top of the base kit waste. |
| Has no line for roof drains, HVAC curbs, or walk pads — each is its own flashed penetration or protected walkway, not a fraction of a blended rate. | Prices drains, curbs, and walk pads as their own hour and material lines, by count or by square. |
| Has no line for stories or access — a one-story garage and a two-story commercial deck of the same plan squares get the same rate. | Adds extra hours per square for a second or third story, so height and access show up in the price instead of being absorbed into it. |
| Gives the crew a number to quote, not a number to check a quote against. | Reports the price per square and the walk-away price alongside the total, so a shopped rate can be scored against real cost before you match it. |
The special's own job, and a job it was never priced for
Using this calculator's own two built-in presets and its own shipped shop-rate defaults — $36 hourly wage, 32% burden, 15% overhead, 25% target margin:
The 12-square TPO-45 recover on a one-story garage (a 40×30 ft plan, two drains, no parapet, no tear-off, no insulation — the job a $650-a-square special is usually built around) takes 23.5 crew-hours and this calculator prices it at $6,527.72 for the job — $543.98 per square, under the $650 headline rate once labor, membrane, and a target margin are actually counted.
The 40.04-square TPO-80 tear-off (an 80×50 ft commercial plan, two layers of polyiso insulation, 80 lf of parapet, six drains, and four HVAC curbs) is a different job at roughly three times the plan squares. It takes 245.3 crew-hours — more than ten times the recover's labor — costs $47,934.71 to run before a dollar of profit, and this calculator prices it at $63,912.94. Quoting that job at the flat $650-a-square rate reproduces $26,026.00 for the job, which is $21,908.71 below its own break-even cost — before counting the $37,886.94 it falls short of this calculator's own price at a 25% target margin. Same unit, same headline rate, one roof that pays and one that loses money before the first parapet seam is welded.
Common questions
Why does a flat $650 per square special get a flat-roof bid wrong?
Because a roofing square (100 sq ft) only measures plan area, not what the job takes to close in. A 12-square TPO-45 recover on a one-story garage -- no tear-off, no insulation, two drains, no parapet -- takes about 23.5 crew-hours on this calculator's own preset. A 40-square commercial tear-off with two layers of polyiso, 80 lf of parapet, six drains, and four HVAC curbs takes about 245.3 crew-hours -- more than ten times the labor at roughly three times the plan squares -- because recover-versus-tear-off, insulation, and parapet detail never show up in a per-square number.
What job is the $650-a-square number actually built around?
One specific job, usually the easiest one a company is willing to advertise: a small, one-story recover over an existing membrane, with no tear-off, no wet insulation, little or no parapet, and few penetrations. It is a marketing price meant to get the phone to ring, not a number derived from any particular building's scope, insulation, or detail work.
How big is the pricing gap in practice?
Using this calculator's own shipped cost inputs on its own two built-in presets: the 12-square TPO-45 recover prices at $6,527.72 for the job -- $543.98 per square, under the $650 headline rate. The 40.04-square TPO-80 tear-off with two layers of polyiso, 80 lf of parapet, six drains, and four HVAC curbs costs $47,934.71 to run before a dollar of profit, and this calculator prices it at $63,912.94. Quoting that job at the flat $650-a-square rate reproduces $26,026.00 for the job -- $21,908.71 below its own break-even cost, before counting the $37,886.94 it falls short of this calculator's price at a 25% target margin.
Is a flat per-square special ever a reasonable shorthand?
For a narrow band of jobs close to the one the special was priced on -- a similar recover, similar membrane, little or no parapet, few penetrations -- a per-square number can land close. The risk is quoting a tear-off, added insulation, or a run of parapet flashing the same way sight unseen, because the rate does not know the scope until the roof is actually measured, and by then the per-square number has often already been quoted.
Does this calculator know my local labor rates or material costs?
No. It has no data on your local labor market or your supplier's membrane, insulation, or flashing pricing. It takes the membrane, scope, slope, stories, plan dimensions, parapet, drains, curbs, and insulation you enter, and your own wage, payroll burden, membrane and insulation cost, dumpster, mobilization, permit, overhead, and target margin, and turns that into crew hours and a price for this job -- the arithmetic a flat per-square special skips, not a market survey.
Nothing here says or implies that quoting a flat per-square special is a bad-faith practice — it is a common, honest way to advertise that works until the roof stops matching the one the special was priced on. This page describes where that shortcut breaks down, not a fault in anyone who uses it. The $6,527.72, $543.98, $47,934.71, and $63,912.94 figures above are this calculator's own arithmetic on its own built-in preset list (open the calculator and pick a starting job from the list to reproduce them), not a claim about any specific contractor's real costs or any specific company's advertised price.
Open the Flat Roof Bid Calculator to price your own job, or read how much to charge for a flat roof.