Pittsburgh’s moist, cloudy climate creates the perfect environment for moss, algae, and lichen to grow on roofs and siding. While many homeowners treat the green or black streaks as just an eyesore, these growths can actually lead to real, costly damage—and the longer they remain, the worse the problem becomes.

Whether your home is in a shaded neighborhood, near trees, or simply exposed to the humidity common in Western PA, exterior growth is more than just a cosmetic issue. In this guide, we’ll break down what these organisms are, why they grow on your home, and the risks they pose if not treated correctly.

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What’s Growing on Your Home? (And Why)

Algae (The Black Streaks)

Algae appear as dark streaks on asphalt shingles and siding. It thrives in humid climates and spreads easily from rooftop to rooftop.

Moss (The Green, Fuzzy Patches)

Moss acts like a sponge—trapping moisture against your roof and siding. It can root into shingle edges, lifting them over time.

Lichen (The Tough, Crusty Spots)

Lichen forms a hard, stubborn crust that bonds tightly to shingles and siding, making it extremely difficult to remove without damage.

Why Pittsburgh Homes Get So Much Growth

• High humidity
• Frequent rainfall
• Tree cover and shaded neighborhoods
• Homes near wooded areas
• Organic debris buildup
• Aging shingles or porous exterior surfaces

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The Hidden Dangers of Exterior Growth

Biological growth looks harmless—but can cause significant deterioration and create expensive repair needs.

1. Roof Damage & Shortened Shingle Lifespan

Moss and lichen trap moisture under shingles, which leads to:

• Curling and lifting
• Granule loss
• Premature shingle failure
• Water penetration

This can reduce your roof’s lifespan by 5–10 years if untreated.

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2. Increased Risk of Leaks

Moisture trapped under heavy moss growth makes shingles more vulnerable to:

• Cracking
• Separation
• Rot

This increases the risk of interior water damage.

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3. Siding Deterioration

Algae and mold on siding can cause:

• Staining
• Oxidation
• Surface breakdown
• Fungal spread into caulking and trim

Vinyl, wood, and fiber cement siding are all vulnerable.

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4. Reduced Curb Appeal

Black streaks and green patches can make a home look unmaintained—even if the interior is spotless. This is especially important if you plan to:

• Sell your home
• Refinance
• Receive appraisals
• Increase neighborhood appeal

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5. Lower Energy Efficiency

Moss and algae hold moisture and can prevent your roof from reflecting sunlight properly, leading to:

• Warmer attic temperatures
• Higher cooling costs

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6. Health Concerns

Unmanaged algae or mold growth can lead to spores entering:

• Windows
• Attic vents
• Soffits
• HVAC systems

This can aggravate allergies and respiratory conditions.

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Why Soft Washing Is the Best Solution

Many homeowners think of pressure washing as the go-to solution, but pressure washing a roof is dangerous and damaging.

Soft washing is the safest and most effective method because it:

• Uses low pressure
• Kills growth at the root
• Prevents regrowth
• Protects shingles and siding
• Maintains manufacturer warranties

Our soft wash system removes:

• Moss
• Algae
• Lichen
• Mold & mildew
• Pollutant buildup
• Organic staining

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When Should You Have Your Roof or Siding Cleaned?

For Pittsburgh homeowners, experts recommend cleaning:

• Every 1–2 years for siding
• Every 2–3 years for roofs
• Immediately if you see moss or lichen patches

If you see discoloration—don’t wait. Growth spreads quickly in humid climates.

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DIY vs. Professional Cleaning: What Homeowners Should Know

DIY Cleaning Risks

• Damaging shingles
• Voiding roof warranties
• Spreading algae spores
• Using the wrong chemicals
• Personal safety hazards

Professional Soft Washing Benefits

• Safe, low-pressure cleaning
• Long-lasting results
• Property protection
• Eco-conscious detergents
• Expert evaluation of roof health

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Pittsburgh Homeowners: Protect Your Home Before Damage Spreads

Moss, algae, and lichen won’t go away on their own—and the longer they remain, the more damage they cause. Whether you’re noticing black streaks, green patches, or tough crusty growths, early action saves you money and extends the life of your home’s exterior.

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Restore Your Home with Safe, Professional Soft Washing

Get a Free Soft Washing Estimate for Your Home

So Clean Solutions helps Pittsburgh homeowners protect their roofs, siding, and exterior surfaces with safe, effective, long-lasting soft washing.

✔ Roof cleaning
✔ Siding soft washing
✔ Mold, mildew, algae, and moss removal
✔ Affordable maintenance plans

👉 Request your free estimate and let us help your home look new again.