Roof Cleaning Methods by Roof Type
What's growing on the roof and what the roof is made of decide the method. A shingle roof with dark streaks, a tile roof with grime in the laps and a shaded slope with moss are three different jobs.
Soft Wash for Algae Streaks on Shingles
The dark streaks running down many shingle roofs are blue-green algae. The Asphalt Roofing Manufacturers Association (ARMA) names Gloeocapsa magma as the most common species and says the problem is most widespread in the Gulf States. ARMA says it's often mistaken for fungus, soot, dirt or tree droppings. Leon County sits in the warm-humid climate zone 2A under the Florida energy code, the conditions ARMA ties to algae growth.
ARMA's method is a solution of household bleach (sodium hypochlorite) and water, applied gently, left on for 15 to 20 minutes, then rinsed with a gentle spray. There's no scrubbing, because friction loosens granules. ARMA also says other chemicals shouldn't be used without the shingle maker's approval, and that the result is temporary: the streaks can come back. HomeGuide prices soft washing at $0.15 to $0.60 per square foot, with $0.15 to $0.20 more on a steep roof and $0.05 to $0.10 to blow debris off first.
Tile Roof Cleaning
Clay and concrete tile get the same soft wash at the same per-foot rate, according to HomeGuide, which also notes that the Roof Cleaning Institute of America and ARMA advise against pressure washing tile. ARMA's advice for shingles, to work from a ladder or walkboards rather than standing on the roof surface, is worth asking about on tile too. Broken pieces are a repair job; tile roof repair covers matching and replacing them.
Moss and Lichen
HomeGuide says moss holds moisture, lifts and curls shingles, clogs gutters and can work under shingles or tile until the roof leaks. HomeGuide lists lichen alongside moss, algae and mildew as signs a roof needs cleaning.
- Moss removal: $0.20 to $0.75 per square foot
- Moss prevention treatment: $100 to $250
- Zinc strips: $30 to $60 per 50-foot roll
HomeGuide warns against zinc sulfate powder, which can wash off the roof and kill the plants below.
Why Pressure Washing Damages Shingles
ARMA's guidance is blunt: don't use a power washer, brush or broom to remove algae, because high-pressure washing is likely to damage asphalt roofing. Malarkey, a shingle maker, warns that pressure washing dislodges the granules that protect a shingle from UV aging. If a cleaning quote mentions pressure washing for a shingle or tile roof, ask for a soft wash instead.
Algae-Resistant Shingles at Replacement
Cleaning buys time, but on an aging roof the better answer can be shingles that resist algae from the start. Copper-coated granules slow algae growth, and Malarkey says that without that protection, streaks can show in as few as three years on a roof in a very humid climate. HomeGuide puts algae-resistant shingles at 5% to 15% more than standard ones. ARMA suggests considering them at reroof on any roof that looks prone to algae. Wind ratings and shingle lines are compared on architectural shingle roofing.
Why Tallahassee homeowners call Tallahassee Expert Roofing
- Your request reaches one roofer, never a call list
- Homeowners pay nothing to use this line
- Ask for the shingle wind class and Product Approval number in writing
- The roofer's estimate is free and you're not obliged to hire
Roof Cleaning Cost, Schedule and Yard Protection
HomeGuide's national figures run from a $150 minimum to about $1,000, with most jobs at $250 to $600. Size, pitch, number of stories and how heavy the growth is set the price. Most roofs take 2 to 5 hours. Plan on one cleaning every one to three years, or a yearly one on a house under a thick canopy.
Bleach solutions are hard on plants and slippery on the roof. HomeGuide says most companies tarp the plants around the house, and ARMA warns the roof becomes slippery and hazardous during treatment, one reason it encourages using professionals. Before the crew starts, ask:
Solution
What's in the mix, and does the shingle maker approve it?Plants
Will beds be covered, and is that in the price?Gutters
HomeGuide prices gutter cleaning at $110 to $185, and many companies discount it when booked with the roof.
HomeGuide also notes that roof cleaners may find damage that needs repair, so ask to be shown photos of anything they flag. Gutters choked with debris are covered on gutter cleaning.