Roof Washing Cost

Roof washing is a cleaning service that removes algae, moss, lichen, mold, and dirt from a roof surface. It uses low-pressure soft washing with a chemical solution of sodium hypochlorite or a surfactant blend to kill organic growth and restore the roof’s appearance without damaging shingles. The cost of roof washing ranges from $250 to $900 per project, with a national average near $475, depending on roof size, pitch, material, and the severity of buildup.

Roof washing protects the roofing surface from the black streaks caused by Gloeocapsa magma algae and the water retention caused by moss. Removing this growth extends shingle life and improves curb appeal. Pricing is usually quoted per project or per square foot of roof area, with most residential jobs falling in the $250 to $600 range.

Cost Overview

Most roof washing companies charge either a flat project rate or a per-square-foot rate. Per-square-foot pricing typically runs $0.20 to $0.60 for soft washing, with steep or heavily soiled roofs pushing toward the top of that range. A standard 1,500 to 2,000 square foot single-story home usually costs $300 to $550.

Minimum service charges are common. Many contractors set a floor of $250 to $350 regardless of roof size because mobilization, setup, and chemical costs are fixed.

Cost by Cleaning Method

The cleaning method has a large effect on price and on the risk of shingle damage.

• Soft washing – $0.30 to $0.60 per square foot. Uses low pressure and a chemical solution to kill growth. Preferred for asphalt shingles and the industry-recommended approach.
• Chemical-only treatment (no rinse) – $0.20 to $0.40 per square foot. A spray-and-leave method where rain rinses the roof over time. Cheapest option.
• Pressure washing – $0.15 to $0.35 per square foot. Cheaper up front but can strip granules and void shingle warranties; used mainly on tile, metal, and concrete.
• Moss removal with scraping – adds $100 to $400. Labor-intensive hand removal for heavy moss mats.

Cost by Roofing Material

Different roofing materials require different techniques and chemical strengths, which changes the price.

Cost by Size and Project Scope

Roof area is the primary driver, but the true measurement is roof surface area, not the home’s footprint. A steep pitch adds 15% to 40% because it increases actual surface area and slows the crew. A cut-up roof with many valleys, dormers, and peaks costs more than a simple gable roof of the same footprint.

1. Single-story ranch, simple roof: $250 – $450
2. Two-story with moderate pitch: $400 – $700
3. Large or complex multi-gable home: $700 – $1,200
4. Heavy moss/lichen restoration: add $200 – $500

You can compare local ranges with a roof washing calculator before requesting quotes.

What Affects the Price

Several named factors move a roof washing quote up or down:

• Roof pitch and height – steeper and taller roofs require harnesses, extended reach equipment, and more time.
• Severity of growth – thick moss mats and deep black streaking need stronger chemicals and repeat applications.
• Accessibility – landscaping, fencing, and tight lots that block truck access add labor.
• Number of stories – two- and three-story homes cost 20% to 50% more than single-story.
• Surface protection – plants, siding, and gutters must be rinsed or covered, adding prep time.
• Region and local demand – humid climates with year-round algae see higher volume and competitive pricing; remote areas cost more.

Labor vs. Materials

Roof washing is labor-dominant. Labor accounts for roughly 70% to 85% of the total, since the chemicals themselves are inexpensive. A typical job uses $20 to $60 in sodium hypochlorite, surfactant, and water. The remaining cost covers a two-person crew for two to four hours, equipment, insurance, and travel.

Expert tip: Insist on soft washing for asphalt shingles. Pressure washing may look cheaper, but blasting granules off the shingles shortens roof life and can void the manufacturer’s warranty. The chemical solution does the work, not the pressure.

DIY vs. Hiring a Pro

A DIY roof wash can cost $50 to $150 for a pump sprayer, a roof-cleaning concentrate, and a garden hose attachment. The savings are real, but so are the risks.

• Fall risk – wet, chemically treated roofs are extremely slippery; falls from a two-story roof are life-threatening.
• Chemical handling – sodium hypochlorite bleaches clothing, damages plants, and irritates skin and lungs.
• Shingle damage – wrong pressure or concentration strips granules and shortens roof life.
• Uneven results – streaks and missed spots are common without the right equipment.

Hiring a licensed, insured pro costs $250 to $900 but includes liability coverage, proper soft-wash equipment, and plant protection. For single-story simple roofs, DIY is feasible for a handy homeowner. For steep, tall, or complex roofs, professional service is the safer value.

Additional and Hidden Costs

Watch for line items that are not always included in the base quote:

• Gutter cleaning – $75 to $200 added on.
• Moss scraping – $100 to $400 for heavy growth.
• Zinc or copper strip installation – $150 to $400 to prevent regrowth.
• Roof repairs – cracked or lifted shingles found during cleaning are billed separately.
• Landscaping restoration – rare, but chemical overspray damage may require plant replacement.
• Trip or minimum fees – $250 to $350 floors on small jobs.
• Warranty/regrowth treatments – some companies offer annual maintenance plans at $150 to $300 per visit.

Ways to Save

Practical ways to reduce roof washing cost:

1. Bundle services – combine roof washing with gutter cleaning or house soft washing for a package discount.
2. Book in the off-season – late fall and winter often bring lower rates in many regions.
3. Clean before growth gets heavy – regular light cleanings cost far less than a full restoration of a moss-covered roof.
4. Get three written quotes – per-square-foot rates vary widely between local contractors.
5. Install zinc strips – a one-time upgrade slows algae return and stretches the interval between washes.
6. Ask about the chemical-only method – if you can wait for rain to rinse, it is the cheapest professional option.

A well-maintained roof washed every two to four years keeps costs predictable and prevents the expensive restoration jobs that heavy neglect creates.