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Roof Washing Services

What Pittsburgh & Westmoreland County Homeowners Need to Know

Roof washing services use a low-pressure soft wash method combined with professional-grade cleaning solutions to safely remove algae, moss, lichen, and black streaks from your roof — without damaging shingles or voiding your warranty. It’s one of the most overlooked home maintenance services, and in the Pittsburgh and Westmoreland County area, it’s something most roofs need every 2–3 years.

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  • If you've noticed dark streaks, green patches, or a general dinginess creeping across your roof, you're not alone. The humid climate across Allegheny and Westmoreland County creates the perfect conditions for algae and moss to take hold — and once it starts, it spreads fast. Professional roof washing services are the safest, most effective way to get rid of it and protect your home's most important asset.
  • security
    Protect your Roof
  • clean house
    curb appeal
  • clock
    Extend Roof Life
  • leaf
    eco-friendly solutions

What Do Roof Washing Services Include?

Professional roof washing services typically cover:

Inspection

of the roof surface before cleaning to identify problem areas, damaged shingles, or areas that need extra care

Pre-treatment

with a biodegradable cleaning solution to break down algae, moss, lichen, and organic staining

Soft wash application

at low pressure — typically under 100 PSI — to rinse the surface without disturbing granules or lifting shingles

Post-rinse cleanup

of gutters, downspouts, and surrounding areas affected by runoff

  • A quality roof washing service protects your shingles, improves curb appeal, and can extend the life of your roof by years.

What Causes Black Roof Streaks?

snow-fungus
Those dark streaks running down your roof aren't dirt or soot — they're Gloeocapsa Magma, a type of blue-green algae that feeds on the limestone filler in asphalt shingles. As it spreads, it leaves behind a dark pigmented sheath that shows up as the black or dark brown streaks you see from the street.
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It's extremely common in humid climates like Pittsburgh and throughout Westmoreland County, where warm summers and moisture-retaining tree coverage create ideal conditions for algae to grow. Left untreated, the algae holds moisture against your shingles, which accelerates granule loss, leads to premature aging, and can eventually compromise the integrity of the roof itself.
snow-fungus
Moss and lichen are two other common culprits. Moss grows in thick green patches (usually on north-facing or shaded areas of the roof) and physically lifts shingles over time. Lichen is even more stubborn — it bonds directly to the shingle surface and is difficult to remove without professional-grade solutions.

What Do Roof Washing Services Include?

  • Feature

  • Soft Wash

  • Pressure Wash

  • PSI

  • Under 100 PSI

  • 1,500–3,500+ PSI

  • Shingle safe?

  • Yes

  • No — strips granules, voids warranties

  • Removes algae at the root?

  • Yes

  • No — blasts surface only, regrowth is faster

  • Safe for all roof types?

  • Most types, yes

  • Not recommended for asphalt shingles

  • Results last

  • 2–5 years

  • 6–12 months

  • Professional recommendation

  • Strongly preferred

  • Generally not recommended

    • Pressure washing blasts the surface clean in the short term, but it strips away the protective granules on asphalt shingles, which shortens the life of the roof. Many shingle manufacturers (including GAF and Owens Corning) specifically recommend against pressure washing and may void your warranty if it's used.
    Soft washing uses biodegradable cleaning agents to kill algae, moss, and lichen at the root level, which means results last significantly longer and the roof surface stays intact.

    Best Methods for Cleaning a Shingle Roof

    For asphalt shingle roofs — the most common type in the Pittsburgh and Westmoreland County area — soft washing is the recommended method. Here’s how professionals approach it:

    roof-inspection

    Pre-inspect

    the roof for damaged, curling, or missing shingles before applying any solution

    pesticide

    Apply a sodium hypochlorite-based or sodium percarbonate cleaning solution

    at low pressure using a soft wash system

    pesticide

    Rinse at low pressure

    (under 100 PSI) from the top down, working with gravity rather than against it

    gutter

    Treat gutters and downspouts

    to clear any runoff from the cleaning solution

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    Apply an optional preventative algae inhibitor

    to slow regrowth

    Important Note For DIYers

    For DIYers, this process is possible but carries real risk — walking on a wet, sloped roof is dangerous, and using the wrong concentration of cleaning solution can damage plants, discolor siding, or harm the shingles themselves. Most homeowners find that hiring a professional roof washing service is worth the cost for the safety and peace of mind alone.

    Safe Cleaning Products for
    Roof Washing

    The three most common professional-grade roof cleaning solutions are:

    flask

    Sodium hypochlorite (bleach-based)

    The most widely used solution for roof washing. Effective at killing algae, moss, and lichen quickly. Must be properly diluted (typically 1–3% concentration) and rinsed thoroughly to protect surrounding plants and landscaping.
    Sodium-hypochlorite
    sodium

    Sodium percarbonate (oxygen bleach)

    A gentler, more eco-friendly alternative. Slower-acting than sodium hypochlorite but safer for surrounding vegetation and less harsh on roofing materials.
    Sodium-percarbonate
    zinc

    Zinc or copper sulfate treatments

    Often used as a post-wash preventative treatment. These inhibit algae and moss regrowth by creating an environment where organic growth can’t thrive.
    Zinc-or-copper
    • What to avoid: Harsh solvents, undiluted bleach at high concentrations, or any cleaner not rated for roofing use. These can break down shingle adhesives, strip protective coatings, and cause long-term damage. If you're DIYing, always rinse surrounding landscaping before and after applying any roof cleaning solution, and check the product label for safe dilution ratios.

    How Much Does Professional Roof Washing and Gutter Cleaning Cost?

    Roof Size
    Estimated Cost
    Small (up to 1,500 sq ft)
    $600–$970
    Medium (1,500–2,500 sq ft)
    $970–$1625
    Large (2,500–3,500 sq ft)
    $1625–$2275
    Extra large / steep pitch
    $2275+
    • The best way to get an accurate number is to request a free estimate from a local roof washing service. Most reputable companies will assess the job before quoting.

    Factors that can affect the price include:

    gutter

    Gutter Cleaning Included

    ensures all roof wash water flows and drains easily

    roof

    Roof pitch and accessibility

    steeper roofs take longer and require more safety equipment

    Severity of growth

    heavy moss or lichen may require pre-treatment and longer dwell times

    Location

    pricing in the Pittsburgh and Westmoreland County area will vary by company

    clean house

    Benefits of Hiring a Roof Washing Service

    fall-protection

    1. Safety.

    Walking on a wet roof is one of the leading causes of home improvement injuries. Professionals have the right equipment, footwear, and harness systems to do the job safely.

    pressure-washer

    2. The right equipment and solutions.

    Professional soft wash systems apply cleaning solution at the correct pressure and concentration, something that's hard to replicate with consumer equipment.

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    3. Longer-lasting results.

    Professional-grade solutions kill algae and moss at the root. DIY methods often only address the surface, which means regrowth happens faster.

    security

    4. Protects your roof warranty.

    Many shingle warranties require proper maintenance, including professional cleaning. Using the wrong method (like pressure washing) can actually void your coverage.

    clean house

    5. Curb appeal and home value.

    A clean roof makes a significant visual difference. For homeowners thinking about selling, a roof washing service is one of the highest-ROI exterior improvements you can make.

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    6. Peace of mind.

    A professional roof washing service will also flag damaged shingles, clogged gutters, or other issues you might not notice from the ground.

    Is Soft Washing Safe for All Roof Types?

    Soft washing is safe for most common roof types, but there are some differences worth knowing:

    roof

    Asphalt shingles

    Fully compatible with soft washing. It’s the recommended method by most shingle manufacturers.

    Asphalt shingles
    roof

    Metal roofs

    Safe for soft washing, though the cleaning solution concentration may need to be adjusted to avoid discoloration.

    roof metal
    roof

    Cedar shake / wood shingles

    Safe, but requires a gentler solution and extra care — wood is more porous and can absorb cleaning agents differently than asphalt.

    Cedar-shake-wood-shingles
    roof

    Clay or concrete tile

    Generally soft wash safe, but high porosity means longer dwell times and thorough rinsing are important.

    Clay-or-concrete-tile
    roof

    Slate

    Requires extra caution. Slate is durable but can be brittle, and the cleaning solution needs to be selected carefully to avoid surface etching.

    Slate
    • Not sure where to start? The Grato team is happy to walk you through our experience with your specific roof type before you book.

    Frequently Asked Questions About Roof Washing Services

    Black streaks are caused by Gloeocapsa Magma, a blue-green algae that feeds on the limestone in asphalt shingles. It’s extremely common in humid climates like Pittsburgh and Westmoreland County and spreads quickly if left untreated.
    Most homeowners pay between $250 and $900 depending on roof size, pitch, and the severity of growth. Request a free estimate from a local roof washing service for an accurate quote.
    Soft washing — using low pressure (under 100 PSI) combined with a biodegradable cleaning solution — is the safest and most effective method for asphalt shingle roofs. Pressure washing is not recommended and can void your shingle warranty.
    Diluted sodium hypochlorite and sodium percarbonate are the most commonly used professional solutions. Avoid undiluted bleach, harsh solvents, or any product not rated for roofing use.
    Safety, longer-lasting results, proper equipment, warranty protection, and improved curb appeal are the top reasons homeowners hire a professional rather than DIYing.
    Soft washing is safe for most roof types including asphalt shingles, metal, cedar shake, and tile. Slate requires extra caution. Always confirm your provider has experience with your specific roof type.

    Glossary

    • soft-wash
      Soft washing A low-pressure cleaning method (under 100 PSI) that uses biodegradable chemical solutions to kill and remove algae, moss, and organic staining at the root level.
    • Magma
      Gloeocapsa Magma The scientific name for the blue-green algae responsible for black streaks on roofs. Common in humid climates.
    • Sodium-hypochlorite
      Sodium hypochlorite A bleach-based cleaning agent widely used in professional roof washing solutions.
    • Sodium-percarbonate
      Sodium percarbonate An oxygen bleach alternative — gentler and more eco-friendly than sodium hypochlorite, slower-acting but safer for surrounding vegetation.
    • Granules The sand-like coating on asphalt shingles that protects them from UV rays and weather. Pressure washing strips these away, shortening roof life.
    • Lichen A slow-growing organism (part algae, part fungus) that bonds directly to shingle surfaces and is more difficult to remove than algae or moss alone.

    Ready to Schedule Roof Washing Services in Allegheny or Westmoreland County?

    At Grato Property Care, we serve homeowners across Pittsburgh, Irwin, Greensburg, and Westmoreland County with professional soft wash roof cleaning that’s safe for your shingles and tough on algae, moss, and staining.

    Learn about our pressure washing and exterior cleaning services or get to know the Grato team before you book. We’re licensed, insured, and stand behind every job with our Grato Guarantee — your roof isn’t clean until you’re satisfied and we’re proud of the result.

    Reach out today to schedule your free estimate.
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