Roof Moss and Algae in Florida
Black streaks on Florida roofs are typically algae (Gloeocapsa magma), not mold or dirt. It's caused by algae feeding on limestone filler in shingles. While primarily cosmetic, algae retains moisture and can shorten roof life. Moss is less common in Florida but grows in shaded areas. Both can be treated with proper cleaning and prevented with zinc or copper strips.
Key Facts:
- • Black streaks are algae, not mold or dirt
- • Florida's humidity creates ideal growth conditions
- • North-facing and shaded areas affected most
- • Soft washing removes algae safely
Algae vs Moss: What's on Your Roof?
Algae (Most Common in Florida)
- Appears as black or dark green streaks
- Flat against the shingle surface
- Spreads via airborne spores
- Thrives in humidity and shade
- Primarily cosmetic concern
Moss (Less Common in Florida)
- Thick, green, fuzzy growth
- Raised from shingle surface
- Grows in consistently shaded, moist areas
- Can lift shingles and cause leaks
- More damaging than algae
Lichen
- Light green or gray crusty patches
- Combination of algae and fungus
- Attaches firmly to shingles
- Difficult to remove without damaging shingles
Need Professional Help?
Gimo's Roofing offers free inspections and estimates throughout Jacksonville and Northeast Florida.
What Causes Roof Algae and Moss?
- Humidity: Florida's 70-80% average humidity promotes growth
- Shade: North-facing slopes and tree-shaded areas retain moisture
- Limestone Filler: Shingle ingredient that algae feeds on
- Debris: Leaves and organic matter hold moisture
- Airborne Spores: Spread from neighboring roofs
Safe Removal Methods
Soft Washing (Recommended)
- Low-pressure application of cleaning solution
- Typically bleach-based or eco-friendly alternatives
- Kills algae/moss, which washes off with rain
- Safe for shingles when done correctly
- Professional service recommended
DIY Cleaning Solution
For DIY cleaning, use:
- 1 gallon water
- 1 quart household bleach (sodium hypochlorite)
- 1/4 cup trisodium phosphate (TSP) or dish soap
- Apply with pump sprayer, let sit 15-20 minutes
- Rinse thoroughly with garden hose (not pressure washer)
What NOT to Do
- No Pressure Washing: Strips granules and damages shingles
- No Scrubbing: Abrasion damages shingle surface
- No Walking: Minimize foot traffic on treated areas
- Don't Ignore Plants: Protect landscaping from runoff
Preventing Algae and Moss Growth
Zinc or Copper Strips
Metal strips installed near the ridge release ions when wet that inhibit algae/moss growth:
- Install 2-4 inch strips below ridge cap
- Zinc is more affordable; copper more effective
- Protects area below the strip
- Lasts 10-20 years
Algae-Resistant Shingles
- Contain copper granules that inhibit algae
- Most manufacturers offer AR versions
- Small premium over standard shingles
- Worth it in Florida's climate
Environmental Controls
- Trim overhanging tree branches
- Remove debris from roof regularly
- Improve air circulation around roof
- Ensure gutters drain properly
Get a Free Roofing Estimate
Instant online pricing or schedule an in-person assessment. Financing available from $99/month.
You Might Also Read
- Roof Maintenance Tips for Florida - Extend your roof lifespan
- Gutter Systems for Florida - Protect your roof and foundation
- Roof Replacement Cost Jacksonville - 2026 pricing guide
Key Takeaways: Roof Algae and Moss
- • Black streaks are algae, common and primarily cosmetic
- • Soft washing is safest removal method for shingles
- • Never pressure wash asphalt shingles
- • Zinc/copper strips prevent future growth
- • Algae-resistant shingles recommended for Florida
Need roof cleaning or algae-resistant shingles? Contact Gimo's Roofing for a free consultation. Call (904) 606-5313.
