Illustration for Metal Roof Cleaning Cost

Panel makers want it done gently, with a hose, mild soap, a soft brush and no blasting.

This September, a washer in a community discussion asked about pricing. Should a metal roof cost more than their usual 28 cents a square foot for shingles? The replies boiled down to this: it depends on the metal, its coating and its condition. Here’s how that plays out for your roof and your bill.

What washers charge for metal

One central Pennsylvania washer publishes a base price of $250 to $400 per 1,000 square feet for metal. That’s a bit under its $300 to $450 for asphalt shingles. It then adds 20% for roofs of 1,501 to 2,500 square feet. It also adds 15% for a medium pitch, 30% for a steep one or 50% for an extreme one.

A Seattle-area roof cleaner’s price guide gives $0.20 to $0.70 a square foot for metal roofs that suit low-pressure washing. A Miami washer lists $0.20 to $0.60 for metal panels. That Miami page says high pressure “may be acceptable.” Some makers disagree, as you’ll see below.

At that Pennsylvania base price, a 2,000-square-foot metal roof comes to $500 to $800. The full $0.20 to $0.70 range stretches that to about $400 to $1,400, and to $600 to $2,100 at 3,000 square feet. All are before any pitch surcharge.

On that Pennsylvania page, pitch moves the price more than the metal does. For other surfaces, see pressure washing costs.

What panel makers allow

Makers’ care guides start in the same place. One says rinsing with a garden hose two or three times a year keeps the paint in good shape. Another says plain hose water removes most dirt. The next step is a mild detergent, about 5% in water. Put it on with a cloth or soft brush and rinse it off.

They split on pressure and bleach:

Maker Pressure washer Bleach Also
McElroy Metal Never; can harm coating or open seams Not covered Stubborn stains: maker-recommended cleaner
ProVia Non-pressure methods always recommended Mildew spot mix with 5% bleach, cloth or soft brush Misused cleaners void surface warranty
Interlock (aluminum) Avoid; can force water under panels Not covered Clean from the ground when possible
Fabral One way to apply detergent Mildew mix with bleach, not on Galvalume Aggressive cleaning may void warranty
MBCI Not covered for routine washing Non-bleach detergents only No wire brushes or abrasives
Western States Metal Roofing Allowed; no more pressure than needed Not covered Steep roof gets slippery when wet

Most agree on no wire brushes, steel wool or scouring pads. One maker’s paint warranty also bars abrasive chemical cleaners. Not sure what your roof is? Look for the maker’s name in your closing papers or warranty. Then ask for its care sheet.

Chalk, rust or growth?

Each one needs a different fix, so figure out which you have first.

  • Chalk. Rub a clean, dry spot. White powder on your finger is chalk. One panel maker explains that UV breaks down the paint’s resin. The resin turns white and wipes off. Its 30-year warranty allows chalk up to a set rating under ASTM D4214. The limit is stricter on walls than on roofs. Heavy chalk is worth raising with the maker. For the same issue on gutters, see oxidation vs tiger stripes.
  • Rust. One maker warns that metal filings left after installation rust overnight. It says to remove the spots with a non-abrasive cleaner. Scratches through the zinc coating need a zinc-rich primer before touch-up paint.
  • Growth and pollen. The makers treat these as two jobs. Detergent lifts dirt, and the bleach mix is only for mildew. In one community discussion, a washer found a 2% bleach spray wouldn’t lift tree pollen and dirt from a metal roof. On a trade forum, a washer was fighting black spots on a metal roof. Others asked if it was Galvalume. Bleach can turn that metal black in places, another poster warned.

In Lexington, Kentucky, May is the wettest month, with 5.44 inches of rain on average. March through May bring about 25 days with a tenth of an inch or more (NOAA 1991–2020 normals).

Why this is a crew job

Panel makers say a metal roof gets slippery. One suggests hiring a skilled pro for roof work. Another notes that steep metal roofs can be slippery. The forum washer above slid a little on a steep roof. Another washer started sliding on a metal barn roof once it got wet.

Crews have rules to follow. OSHA’s rule covers workers on a home 6 feet or more up. It calls for guardrails, safety nets or a personal fall arrest system. A “steep roof” is anything steeper than 4 in 12. OSHA’s fall protection pages are the authority. For homeowners, the makers’ advice is simple: stay on the ground.

What to ask before you hire

  1. Do you know what my roof is (painted, bare Galvalume or aluminum)? Will you follow that maker’s care sheet?
  2. What cleaner and what pressure will you use?
  3. How will you tie off on a wet roof?
  4. How will you protect my plants? One maker says to keep cleaners off shrubs.
  5. What’s the price per square foot, and is there a pitch surcharge?

Our questions to ask a house washing company covers insurance. Still deciding? Read is roof cleaning worth it and what to expect after a roof soft wash. How we check numbers: our methodology.

Sources

Based on 17 sources · How we price