How to Price Roof Cleaning Per Square: Footprint and Pitch

Here is how to price roof cleaning per square without climbing the roof to measure it. Trace the footprint from satellite, read the pitch at the gable end and multiply by the published pitch factor for the true surface area. Divide by 100 for squares, price each square against a dated survey range, and put the chemical, dwell and fall protection underneath.

What a roofing square is, and how to price roof cleaning by it

A square is 100 sq ft of roof surface, so a 1,789 sq ft roof is 17.89 squares and is quoted as 18. The Asphalt Roofing Manufacturers Association's glossary defines it as "A unit of roof measure covering 100 square feet."

The surface is larger than the footprint, which Roof Online defines as the area a roof covers regardless of slope, "the apparent area of a roof when you look straight down at it, like from a satellite," so every roof price starts with two numbers: footprint and pitch.

Step 1: Measure a roof from satellite, section by section

Trace each roof section as its own shape, read the plan-view area, and add the shapes up.

1. 1Step 1: Enter the address and pick the clearest imagery date: leaf-off, no shadow from a taller neighbor.
2. 2Step 2: Trace the main roof along the outer edge of the eaves, overhang included, and close the shape at the first point.
3. 3Step 3: Trace a garage, porch or dormer as its own shape when its pitch differs; each gets its own factor in Step 2.
4. 4Step 4: Note what changes the job: solar panels, a skylight, moss along the north eave.

The free satellite tool traces the roof outline for plan-view square footage with no account; its page says to multiply by your pitch factor for true surface area (about 1.05 for 4/12, 1.12 for 6/12, 1.20 for 8/12) and, in its own words, "MakeHay measures the footprint; it does not detect pitch or facets." In MakeHay, a saved measurement attaches to the job site and Use in line fills a per square foot quote line; the satellite measurement page says to measure on site where inches matter.

Step 2: Read the pitch and apply the roof pitch multiplier

Pitch is the rise in inches over 12 inches of run, and the place to read it without walking the roof is the gable end. InspectApedia's roof measurement guide marks 12 inches horizontally along the sloping gable trim from a ladder, then measures "vertically straight up to the edge of the same sloping gable end trim"; that distance "is the roof rise in inches per foot of run." A 5 inch rise is a 5/12 roof.

Roof Online says that "Eyeballing the slope and guessing" is "probably not a good idea," and that phone pitch apps pointed at a clear gable end "can be acceptably accurate sometimes." The ladder reading is the one to trust; the app is a check. Roof Online's factor is the square root of ((rise ÷ run)² + 1), and "for a roof with a slope of 6:12, that number, 1.118," is what you multiply by.

Multiply each section by its own factor, add the results, and divide by 100 for the squares on the quote. When the reading falls between two rows, take the steeper one and say so on the quote.

Step 3: Roof cleaning cost per square foot in the consumer surveys

Two homeowner surveys agree on the soft wash band. Fixr's survey, updated January 31, 2025, prices a soft wash at $0.30 to $0.75 per sq ft. This Old House's guide, updated March 31, 2026, puts professional cleaning at $0.20 to $0.70 per sq ft and $300 to $1,050 for a 1,500 sq ft roof.

This Old House says its prices scale with roof size, which "will be slightly larger than your home's square footage due to overhangs and roof pitch," so apply the band to the surface from Step 2, the area you spray. It also prices steepness: "steep roofs may require cleaners to use extra safety equipment, which will cost up to $0.15 more per square foot." The band is the market, not your cost; the next two steps decide where in it you can sit.

Step 4: The cleaning method the shingle makers publish

The Asphalt Roofing Manufacturers Association publishes the method on its algae discoloration page. Discoloration "may be lightened by applying a solution of liquid household bleach (sodium hypochlorite) and water," the solution "should be gently dispersed on the roofing surface," and it "should be left on the roof for at least 15 minutes but no more than 20 minutes".

• No scrubbing: "Avoid scrubbing the surface, as this friction may loosen and remove granules."
• No pressure: "DO NOT use a power washer or any type of brush or broom."
• Stay off the shingles: "always work from a ladder and/or walkboards."
• Nothing else without a signature: "Other cleaning chemicals or methods should not be used without the approval of the shingle manufacturer."

ARMA gives no ratio; it says mixing directions "may vary among shingle manufacturers," so the mix comes from the shingle maker's care page or your surfactant label. It also says the cleaning "is only temporary, and the discoloration may recur," which makes a one-time job a repeat one.

Step 5: Chemical, dwell time and fall protection

Chemical is priced from your supplier's invoice. For a published reference, Leslie's lists a two-pack of 1 gallon bottles of liquid chlorine, sodium hypochlorite at 10 to 12.5 percent available chlorine, at $15.99 on October 13, 2026, about $8 a gallon. Price chemical as gallons times your figure.

Dwell is time on the clock: ARMA's 15 to 20 minutes is idle time for the sprayer, and a large roof done in sections stacks the waits. Time three roofs from setup to rinse and use that pace.

Fall protection is the cost left out most often. Under the US OSHA general industry rule, 29 CFR 1910.28(b)(13), an employee working on a low-slope roof less than 6 feet from the edge needs a guardrail, safety net, travel restraint or personal fall arrest system, and from 6 to 15 feet the same, with a designated area allowed only for work that is both infrequent and temporary. OSHA's definitions in 1910.21 make a low-slope roof 4 in 12 or less; on a steeper roof the general rule in 1910.28(b)(1) applies, any unprotected edge 4 feet or more above a lower level.

For the price that means rigging time: an anchor, a lifeline and a harness go up before the first gallon and come down after the rinse. Time it once and quote it as its own number.

Good to know: This is general information, not legal advice. Statutes and rules change; read the current text and ask your state licensing board or a lawyer before you rely on it.

Soft wash roof cleaning price versus pressure, and the warranty

Both surveys price a soft wash above a chemical wash, and the soft wash is the method that matches what the shingle makers describe; the warranty is the reason to sell it. This Old House's guide says aggressive cleaning can strip granules and that "You may also risk voiding your roof's warranty," and ARMA says the same from the manufacturers' side: no power washer, no brush, no broom.

Tell the customer: the job follows the method the asphalt shingle manufacturers' association publishes, nothing touches the shingles with pressure or a brush, and anything beyond bleach and water goes on only with the shingle maker's approval, so ask for the shingle brand first.

Put it in the quote in one line: "Soft wash to the asphalt shingle manufacturers' published method; no pressure, no scrubbing." The warranty is the homeowner's document; the quote names your method and promises nothing about it.

Scheduling around dry days and writing the quote

A soft wash needs dry shingles while the solution dwells, so rain in the forecast is a reason to move the visit, and the quote needs a line per roof section, one for gutters and one for the method.

In MakeHay, the pressure washing starter list carries "Roof soft wash" per square foot and "Gutter brightening" per linear foot; the invoice below shows 2,180 sq ft of roof soft wash. The suggested "Soft wash" weather rule is max rain 30 percent, checked the day after, on the National Weather Service forecast for the house's own address, US only (plan around the weather).

Show the arithmetic on the quote: footprint, pitch, factor, surface and rate. Gutters come by the foot from the same trace (the perimeter is eaves plus rakes, so take off the gable ends); pricing gutter cleaning per linear foot covers that line, estimating a pressure washing job without a site visit covers the rest of the house, and pressure washing startup costs covers the rig.