What Roof Cleaning Is and Why It Matters
Those dark streaks on your roof aren't just dirt - they're a living organism eating your shingles.
I'm Ken McClary, owner of Wash NWA, and I provide professional roof cleaning across Northwest Arkansas. If you've noticed black streaks, dark staining, or green patches on your roof, you're looking at biological growth that's actively damaging your roofing material. It's not cosmetic - it's a problem that gets worse every month you leave it untreated.
The dark streaking you see on roofs throughout NWA is caused by a blue-green algae called Gloeocapsa magma. This organism feeds on the limestone filler in asphalt shingles, and it produces a dark pigmented sheath to protect itself from UV rays. That protective layer is what creates the black streaks running down your roof. Once Gloeocapsa magma takes hold, it spreads steadily across your entire roof surface. It starts on north-facing slopes where moisture lingers, then colonizes the rest.
Beyond algae, NWA roofs also develop moss in shaded areas, lichen on older shingles, and accumulated organic debris from our dense Ozark forests. Moss is particularly destructive because it lifts shingle edges as it grows, letting water seep underneath and causing leaks, rot, and structural damage. Lichen bonds tightly to shingle surfaces and can leave permanent pitting if left too long.
Professional roof cleaning removes all of this growth safely, restores your roof's appearance, and extends the life of your roofing material by years. It's one of the smartest investments a homeowner can make, especially considering that a new roof costs ten to twenty times what a professional cleaning does.
Get a Free Roof Cleaning QuoteWhy I Soft Wash Roofs - Never Pressure Wash
Pressure washing a roof destroys it. Here's the right way to clean a roof, and exactly how I do it.
Let me be absolutely clear about something: you should never pressure wash a roof. High-pressure water strips the protective granule layer off asphalt shingles, blasts away roofing cement, and can crack or dislodge tiles. It voids manufacturer warranties from GAF, Owens Corning, CertainTeed, and every other major brand. The Asphalt Roofing Manufacturers Association (ARMA) specifically recommends low-pressure chemical cleaning - soft washing - as the only approved method for cleaning asphalt roofs.
That's exactly what I do. Here's my process:
- Ground-level assessment. I inspect your roof from the ground, identify the type and severity of biological growth, note your roofing material, roof pitch, and any areas needing special attention. I also check your gutter condition and note all landscaping below the roofline that needs protection.
- Property protection. Before any cleaning solution touches your roof, I thoroughly wet down all plants, shrubs, grass, and landscaping around the entire perimeter of your home. Sensitive plantings get additional protection. I also check that windows and doors are closed.
- Soft wash solution application. Using specialized low-pressure equipment, I apply a professional-grade cleaning solution across your entire roof surface. This solution is specifically formulated to kill Gloeocapsa magma, moss, lichen, and other biological growth at the root level. The pressure I use is comparable to what comes out of a garden hose - nowhere near enough to disturb your shingles.
- Dwell time. The cleaning solution needs time to penetrate and neutralize the organisms. During this period, the active ingredients break down the biological growth at the cellular level, causing it to release its grip on your shingles. This is the critical step - the chemistry does the work, not mechanical force.
- Gentle low-pressure rinse. I rinse the entire roof from the ridge down to the eaves using low pressure, washing away the dead organisms and cleaning solution. Working from top to bottom ensures everything flows naturally off the roof rather than getting pushed under shingle edges.
- Post-rinse plant care. I do a thorough final rinse of all landscaping and surrounding hardscape to dilute any cleaning solution that dripped down during the process.
- Final walkthrough and inspection. I examine the completed work from multiple angles around your property to confirm complete, even coverage. Any areas that need additional attention get treated on the spot.
Most roof cleaning jobs take 2 to 4 hours depending on roof size and the severity of growth. You'll see dramatic results immediately, and the treatment continues working for weeks after application, killing any remaining spores deep in the shingle texture.
Roofing Materials I Clean Safely
Every roof type in NWA gets a customized approach. Here's what I work with.
- Asphalt shingles (3-tab and architectural) - By far the most common roof type across Northwest Arkansas. This is what I clean most often, and soft washing is the manufacturer-recommended method. My process kills algae and moss without disturbing the protective granule layer that shields your shingles from UV damage. Whether you have basic 3-tab shingles or dimensional architectural shingles, the approach is the same and the results are dramatic.
- Metal roofing - Standing seam and corrugated metal roofs are growing in popularity around Bentonville, Fayetteville, and the newer developments in NWA. Metal roofs develop oxidation, algae staining, and discoloration over time. I adjust my solution concentration and technique for metal surfaces, removing the growth and restoring the original finish without scratching or dulling the surface.
- Tile roofing - Clay and concrete tile roofs are less common in NWA but present on some homes, particularly in higher-end neighborhoods. Tile is porous and holds biological growth deep in its texture. My soft wash process cleans tile thoroughly without cracking, chipping, or dislodging individual tiles.
- Cedar shakes - Some of the older and more upscale homes in Bella Vista, west Rogers, and the hills of Fayetteville have cedar shake roofs. Cedar requires the most careful approach - I modify my solution strength to protect the wood while still eliminating moss, algae, and lichen. The results on cedar are stunning, revealing the warm wood tones underneath years of biological buildup.
- Composite and synthetic shingles - Newer synthetic roofing materials found in recent NWA construction. I treat these similarly to asphalt with excellent results.
If you're not sure what type of roof you have, don't worry. I'll identify it when I assess your property and use the appropriate solution and technique for your specific material.
Signs Your Roof Needs Professional Cleaning
NWA's humid Ozark climate makes roof cleaning a necessity, not a luxury.
Northwest Arkansas is one of the toughest environments in the country for roofs. Our combination of warm, humid summers, frequent rainfall, heavy tree canopy, and mild winters creates ideal conditions for Gloeocapsa magma, moss, and lichen to thrive. Most NWA roofs start showing visible algae growth within 3 to 5 years of installation, and the growth accelerates from there.
Here are the signs that your roof needs cleaning:
- Black streaks running down your roof. This is Gloeocapsa magma algae, and it's the number one reason homeowners call me. Once you notice it, it's already well-established and spreading. It typically starts on the north-facing slope and works its way across.
- Green moss on shaded sections. Moss is common on roofs under heavy tree cover, especially in the wooded neighborhoods of Bella Vista, west Fayetteville, and the hillier parts of Rogers. Moss lifts shingle edges and causes leaks if left untreated.
- Your roof looks significantly darker than it used to. When algae covers an entire roof evenly, homeowners sometimes don't notice because the change is gradual. If your roof looks darker than your neighbor's similar-aged roof, algae is likely the reason.
- Your energy bills have increased. A roof covered in dark algae absorbs more heat than a clean roof, forcing your air conditioning to work harder during our hot NWA summers.
- Your HOA has sent a notice. Several NWA neighborhoods and HOAs require roofs to be maintained free of visible staining. Professional cleaning is far cheaper than the fines or a premature roof replacement.
- You're planning to sell your home. A stained roof signals neglect to potential buyers and can reduce your home's appraised value. Cleaning your roof before listing is one of the best returns on investment in real estate preparation.
I recommend roof cleaning every 2 to 3 years for most NWA homes. Roofs with heavy shade or north-facing orientation may need cleaning more frequently. After a professional soft wash, the treatment continues inhibiting re-growth for an extended period.
Roof Cleaning Across NWA
I clean roofs throughout Northwest Arkansas. Find your area below for local details.
I serve all of Northwest Arkansas including Bentonville, Fayetteville, Springdale, Bella Vista, and surrounding communities. View all service areas.
Roof Cleaning Questions
Answers to the most common questions I hear from NWA homeowners about roof cleaning.
Why can't I just pressure wash my roof?
Pressure washing strips the protective granules off asphalt shingles, which shortens their lifespan dramatically and voids your manufacturer's warranty. It can also crack tiles, split wood shakes, and force water under roofing materials causing leaks. ARMA and every major shingle manufacturer specifically recommend soft washing as the only approved cleaning method. I follow those guidelines on every job.
What are those black streaks on my roof?
Those streaks are caused by Gloeocapsa magma, a blue-green algae that feeds on the limestone filler in asphalt shingles. It produces a dark pigment to protect itself from UV rays, which creates the black streaking pattern. It's extremely common in humid climates like Northwest Arkansas and it spreads across your entire roof over time if left untreated.
Will the cleaning solution damage my plants?
No. I thoroughly wet down and protect all landscaping before, during, and after the cleaning process. My solutions are biodegradable, and the dilution from my plant protection protocol keeps everything safe. I've never had a plant casualty from a roof cleaning job.
How long do the results last?
Most NWA homeowners see 2 to 3 years before noticeable algae returns after a professional soft wash. The treatment kills existing growth and continues inhibiting new growth for an extended period. Roofs in heavy shade or north-facing slopes may see re-growth sooner, while roofs in full sun stay cleaner longer.
Will roof cleaning extend my roof's life?
Yes. Algae feeds on the limestone filler in your shingles, slowly degrading them. Moss lifts shingle edges and causes moisture damage. Removing this growth and keeping it at bay through regular cleaning can add years to your roof's functional life. It's significantly cheaper than an early roof replacement.
Do I need to be home during the cleaning?
Not necessarily. As long as I have access to a water spigot and the property, I can complete the work while you're away. I'll send you before-and-after photos when the job is done. Many of my customers are at work during their roof cleaning appointment.
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