Step 1 — Split the building by zone, not by total area
Your store has one square footage on the property record and a different one in a cleaning scope, because half of what is under the roof is either excluded or cleaned to a much lower spec. Parts storage, mezzanines, the wash bay and the technicians' locker area are usually out. What remains divides into surfaces that behave completely differently under a machine.
Step 2 — Count fixtures before you measure floors
Restrooms are not priced by area. They are priced per fixture, and the times are itemised:
| Fixture | Minutes each |
|---|---|
| Commode | 3.83 |
| Urinal | 3.00 |
| Wash basin with dispenser | 3.00 |
| Mirror | 0.66 |
| Waste receptacle | 0.50 |
Fixture time alone undercounts a restroom by nearly half, because it does not include the floor, the doors, restocking or the walls behind the urinals. We load it by 1.9 to cover that. In the worked example below, 14 fixtures across four restrooms come to 42.3 hours a month — 36% of the whole job.
This is the single number that decides whether a dealership quote is right or wrong. Two stores of identical square footage with different restroom counts are different jobs, and a bidder who quoted you from a floor plan without walking the restrooms has guessed.
Step 3 — Apply the production rate for the tool, not the room
Published rates are per task and per tool. A 24-inch autoscrubber is rated at 10,000 square feet an hour; a 22-inch upright vacuum at 4,348; a 36-inch push broom at 5,556. The room does not appear in the calculation at all — only what you are doing and what you are doing it with.
Be careful with any table you are shown that lists rates "by space type" — showroom, office, warehouse. Those circulate widely and cite no edition, page or source. We went looking for where they come from, and the answer is not flattering.
Step 4 — De-rate for what is actually in the way
Published rates assume an empty floor. A showroom has vehicles parked on it, offices have furniture, and a service bay has lifts, tool carts, air lines and a parts washer. We apply:
| Zone | Of nominal rate |
|---|---|
| Showroom | 65% |
| Offices | 60% |
| Customer lounge | 65% |
| Service drive | 80% |
| Service bays | 50% |
| Parts department | 70% |
These are estimator's judgement, not published constants, and we say so. The published tables do carry their own theoretical-versus-practical split, and the gap is not one number either: it runs over twofold for walk-behind autoscrubbers but only about 1.27 times for riding sweepers.
Step 5 — Add the time that does not scale with area
Travel to site, unloading and loading equipment, security check-in, lock-up and the trash haul. We budget 27 minutes per visit per building. This is why a small store prices high per square foot and why a three-building campus is not three times the work of one — and why leaving it out is the most common way a contractor loses money on a single-point dealership.
Step 6 — Multiply by frequency, then amortise the periodics
Frequency is per zone, not per building. Most stores run the showroom and restrooms five or six nights, parts twice a week and bays on a separate cycle. Then extraction, scrub-and-recoat, high dusting and exterior glass are amortised across the year rather than billed as surprises — we budget 7% of monthly hours and list each one with its interval in the proposal.
A month is 4.33 weeks, not four. Using four understates every monthly figure by eight percent — an error that survives in a surprising number of bids.
The worked example
A single-building store, 13,000 square feet in scope, four restrooms, five nights a week with bays on a three-times-weekly cycle and parts twice.
| Zone | Sq ft | Per week | Hours/month |
|---|---|---|---|
| Showroom | 3,500 | 5 | 11.7 |
| Service drive | 1,800 | 5 | 4.9 |
| Offices | 2,200 | 5 | 18.3 |
| Customer lounge | 900 | 5 | 6.9 |
| Parts department | 1,600 | 2 | 1.6 |
| Service bays | 3,000 | 3 | 14.0 |
| Restrooms (14 fixtures) | — | 5 | 42.3 |
| Fixed time per visit | — | 5 | 9.8 |
| Periodics, amortised | — | — | 7.7 |
| Total | 13,000 | 117.1 |
Now check your own arithmetic
Two tests before any number leaves the office.
Square feet per labour hour. This build lands at 2,406. If a dealership build comes out far outside roughly 2,000–4,500, something is wrong — usually a zone counted at its nominal rate without de-rating, or restrooms priced by area.
Revenue per labour hour. Divide the price by the hours. Below about $22 an hour you cannot pay a legal loaded wage, let alone supplies, supervision, insurance and profit. This one test kills more bad bids than any other, and it is the reason a suspiciously cheap quote is not a bargain — it is a contractor who will be back in four months asking for more or gone entirely.
Only then do we compute dollars per square foot, purely as a check against our own history: $0.297–$0.342 a month here. It is an output, never an input. Where the hourly rate comes from.
What you should get in a proposal
- The zone list with square footage and frequency for each
- The restroom fixture count that was actually walked and counted
- Total crew hours per month, and the crew size and shift that delivers them
- Bays and day porter as separate lines with named specs
- Periodics listed with intervals, not "as needed"
- What is explicitly excluded — in writing, before anyone signs
If a proposal shows you a monthly price and nothing else, you cannot tell whether it is cheap because they are efficient or cheap because they are not planning to do half of it.