Per square foot or per line item

A homeowner asks what you charge per square foot. You give the number you always give, because it has worked for years and because "it depends" loses the call. Then you show up: a 1920s bungalow, cracked plaster, six small rooms, and a stairwell you cannot get a ladder up.

The unit price did not lie about the square footage. It lied about the work.

Two 1,800-square-foot paint jobs, $2,200 apart in cost

Every number below is invented so the arithmetic is easy to follow. Your burdened rate and your production will be different; the shape is the point.

Both jobs are 1,800 square feet of paintable wall surface. Your interior number is $2.10 per square foot and your burdened crew cost is $48 an hour, so both estimates come out at $3,780. Say which surface you measured: "per square foot" means wall area to some painters and floor area to others, and a house has roughly two and a half to three times more paintable wall than floor.

Job A is a new-construction great room and hallway: 10-foot ceilings, primed drywall, empty house, one color, ground floor. Two painters, a day and a half each.

Job B is that bungalow: six rooms, 22 inside and outside corners, 14 windows, nine doors, plaster to patch, three colors, occupied, half of it upstairs. Two painters, four days each.

The whole 40-hour gap traces back to conditions already listed in Job B's description. Job B is Job A plus those conditions:

Forty hours at $48 is $1,920. Add one more day of travel, loading and unloading ($144) and the extra compound, primer and third color ($180), and you have the $2,244.

Same unit, same quantity. Job A subsidizes Job B, and you find out at year end — if your job costing is good enough to tell you.

The five conditions that break a unit price

Setup does not scale. Drive, unload, cover, mask, mix, clean up, reload. That block runs roughly the same whether you cover 200 square feet or 2,000, and on a small job it can eat half the day. Time it on ten jobs and you will have your own number. A four-square roof repair — 400 square feet, since a roofing square is 100 — still needs disposal arranged, a delivery staged and a permit if your jurisdiction requires one. Many do not; your building department sets that line.

Cut-up space costs more per foot. Area is what you price; perimeter is what you work. One great room and six bedrooms can hold identical square footage with a completely different edge count. Flooring installers see it in waste: 5% only for a single square room laid straight, which almost no house is; 10% with doorways, closets and a bump-out; 15% or more on a diagonal layout, where every board at the wall is mitered twice. Manufacturers publish waste guidance per product — follow that, not a rule of thumb.

Height and access. Second stories, narrow stairwells, no driveway to stage from, a condo elevator you have to book. Roofing prices this openly: steeper pitches and second-story work carry their own adders, because production drops and fall protection changes the setup.

Prep varies more than the finish. A pour over prepared subgrade and one where you first break out a failed slab are the same square footage. So are primed drywall and plaster with 30 cracks. The finish is predictable; the prep is where the hours disappear.

Obstacles the tape measure never sees. Furniture to move, tenants in place, pets, one working bathroom, restricted delivery windows, a dumpster with nowhere to sit.

None of this is a painting problem. A roofing square hides pitch, tear-off layers and decking repair. A linear foot of gutter hides corners and terrain. A per-room cleaning price hides room size and condition.

Test your unit price against your last ten jobs

Take ten finished jobs of the same type and divide each one's total cost by its units. That is the unit price the job actually needed.

There is no industry threshold for how tight that spread should be, so do not trust one that sounds official. Look at the shape. If the ten numbers cluster, the unit price is doing real work. If your worst job needed roughly double what your best did, you are averaging and the easy jobs are carrying it. Narrow the unit to a job type that behaves consistently, or stop leading with it.

Price by line item, present by the unit

Build the estimate internally as line items — labor hours by task, materials by quantity, mobilization, disposal, then overhead and profit. Present it in whatever form the customer can compare: one number, a unit price, or the line items if they are bidding it out. It stays honest as long as the unit price falls out of this job's takeoff, not out of memory.

Where the unit price stops being honest

Three things hide what the customer should know: an undefined unit — "per square" that may or may not include tear-off, disposal and decking repair; prep excluded but the exclusion never written down; and a quantity called approximate with nothing saying what happens if the field measurement differs. That last one belongs in the estimate as a change order term, agreed before you start, not discovered on the invoice.

No federal rule requires any of it; there is no national law about what an estimate must itemize. It is how you stay out of a dispute you would lose on the facts. But your state may make parts of it law. California requires a residential home improvement contract over $500, and any change to that contract, to be in writing and signed by both parties before the work it covers begins (Business and Professions Code §7159). Other states have their own home improvement contract rules, and they differ on thresholds, required clauses and cancellation rights. Your state contractor licensing board publishes yours — read it once; the neighboring state's rule does not travel.

Building the estimate this way in DoneQuote

DoneQuote drafts estimates as line items priced from your own catalog — the internal build this article is about. What the customer sees stays your call: full detail, one total, or the unit price with the inclusions and exclusions underneath.

Summary

• A unit price is an average; averages fail on small, cut-up, high-access and heavy-prep jobs
• Run your last ten jobs through it; a wide spread means you are averaging
• Build by line item, present by whatever the customer can compare
• Write down the quantity, the inclusions, the exclusions and what happens if the measurement changes — then check what your state requires

The number itself is not the problem. Quoting it before you have seen the job is.