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Moss and Algae Roof Treatment

Reference Process Updated Jul 24, 2026 ยท Roofing

Why this matters

Moss + algae on asphalt shingles cause functional damage (lifting shingles, retention of moisture, reduced service life) + aesthetic concerns. Customers in shaded / humid climates often face this issue. Roofing contractors offering treatment + prevention serve both immediate need + long-term roof care.

Difference: moss vs. algae

Moss:

  • Green plant growing on the roof
  • Roots lift shingles
  • Retains moisture
  • Reduces shingle life
  • Aesthetic + functional concern

Algae:

  • Streaks / discoloration (typically blue-green or black)
  • Doesn't lift shingles directly
  • Aesthetic concern primarily
  • Reduces shingle reflectance

Different treatment for each.

Common species

For algae:

  • Gloeocapsa magma (most common black streak)
  • Common in humid + shaded conditions
  • East-west streak pattern often (from rain runoff)

For moss:

  • Various green species
  • Thrives in shade + moisture

Customer's environment

For moss / algae:

Factor Effect
Shade (north-facing) More moisture; more growth
Trees overhanging Leaves + shade; more growth
Humid climate More growth

Treatment options

Zinc / copper strips

For prevention:

  • Strips installed at the ridge
  • Rainwater picks up metal ions
  • Ions inhibit growth
  • Customer's long-term protection

Modern preventive method.

Roof cleaning (chemicals)

For existing growth:

  • Specialty cleaners
  • Multiple types available (bleach-based, sodium hydroxide-based, specialty)
  • Customer's specific cleaning
  • Professional application

Customer's investment in cleaning.

Pressure washing

For aggressive cleaning:

  • High-pressure water
  • Risk of shingle damage
  • Not recommended for most asphalt

Use carefully.

Mechanical removal

For moss:

  • Brushing off the moss
  • Less aggressive than washing
  • Combined with chemical

Effective.

Treatment procedure

Step 1: Survey

  1. Identify the growth (moss vs. algae)
  2. Identify extent
  3. Customer's expectations

Step 2: Pre-treatment

  1. Remove loose debris
  2. Document with photos

Step 3: Apply treatment

  1. Per manufacturer + safety
  2. Customer's home protection (downspouts, plants)

Step 4: Wait + monitor

  1. Allow chemicals to work

Step 5: Rinse / clean

  1. Remove dead organisms

Step 6: Preventive measures

  1. Install zinc strips
  2. Customer's long-term protection
  3. Customer's investment

Customer protection

For chemical treatment:

  • Cover plants / landscape
  • Customer's gutter / downspout coordination
  • Customer's pets / family

Care during treatment.

When to recommend cleaning

Customer situation Recommendation
Visible streaks affecting aesthetic Cleaning
Moss lifting shingles Cleaning + prevention
Customer's roof aging Cleaning + assessment
Customer planning to sell Cleaning

Customer's investment.

When the customer asks "what about my roof?"

For specific homes:

  • Algae-resistant shingles available (new)
  • Customer's specific climate
  • Customer's long-term

Customer's reroof opportunity.

Algae-resistant shingles

For modern asphalt:

  • Copper granules in the shingle
  • Reduces algae growth
  • Customer's specific manufacturer
  • Customer's investment

A common feature in modern shingles.

When the customer's roof is old

For aged roofs:

  • Treatment less beneficial
  • Customer's reroof opportunity
  • Customer's investment

Consider reroof.

Damage from moss

For severe moss:

  • Lifted shingles
  • Water entry below
  • Customer's roof damage
  • Customer's reroof needed

Significant when severe.

Customer education

For moss / algae:

  1. "Your roof shows [moss/algae]"
  2. "Treatment + prevention possible"
  3. "Customer's specific climate matters"
  4. "Customer's long-term roof protection"

A clear conversation.

Customer's homeowner association

For some properties:

  • HOA may not allow visible algae streaks
  • Customer's cleaning required

Verify.

Cost framework

For treatment:

Service Cost relative
Standard roof cleaning Baseline
Premium cleaning 1.5-2x
Cleaning + zinc strips 2-3x
Major moss removal 3-5x
Reroof if damage 50-100x

Customer's investment vs. damage prevention.

Coordination with reroofing

For comprehensive:

  • Clean before reroof not needed (replaced)
  • Treatment after reroof for prevention
  • Customer's complete approach

Customer's specific timing.

Common pitfalls

  • Pressure washing damaging shingles
  • Wrong chemicals for the situation
  • Customer expects permanent fix - periodic treatment needed
  • No prevention - recurrence

Standard care.

Specialty: green roof / living roof

For some customers:

  • Green roof with intentional plants
  • Different from unwanted moss

Specialty installation.

When the customer can DIY

For some customers:

  • Light algae treatment customer-side
  • Customer's specific safety
  • Roof access

Sometimes DIY-able.

When professional is recommended

For:

  • Severe growth
  • Roof access concerns
  • Customer's safety

A professional approach.

Insurance considerations

For damage:

  • Some insurance covers moss damage (depends)
  • Customer's specific policy

Verify.

Annual maintenance

For ongoing:

  • Customer's annual inspection
  • Address any growth promptly
  • Customer's preventive measures
  • Customer's long-term

Standard maintenance.

Customer's neighborhood

For variable:

  • Customer's specific exposure

Customer-specific.

Final notes

Moss + algae treatment is:

  • Customer's home maintenance
  • Customer's roof protection
  • Customer's investment
  • Long-term protection

A meaningful service.

References

  • Manufacturer documentation (Roof Wash, etc.)
  • NRCA installation guides
  • Asphalt Roofing Manufacturers Association
  • Customer's specific climate considerations
  • Manuall internal: Asphalt Shingle Types, Replace Damaged Shingles, Roof Inspection Process SOP

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