Roof Algae, Mold and Wood Rot in Sarasota

Why Do Florida Roofs Grow Algae, Mold and Rot?

Warm temperatures, high humidity, frequent rain and shade from trees give algae, lichen and mold everything they need. Wood under the roof rots when it stays wet, which usually means a leak, poor ventilation or water getting behind fascia and gutters. Pests follow damaged or open wood.

The difference that matters is whether the growth sits on the surface or points to moisture inside the roof. Surface algae is a cleaning question; mold, rot and pests are a roofing question.

What Are the Black Streaks on My Roof?

The dark streaks on many Sarasota roofs are colonies of algae, most commonly Gloeocapsa magma. They usually start on the north-facing or shaded slopes and run down the roof in streaks. The algae is mostly cosmetic and doesn't by itself mean the roof is failing.

The Asphalt Roofing Manufacturers Association advises against pressure washing asphalt shingles, because it strips the protective granules. Discoloration can be lightened with a gentle, low-pressure application of a diluted bleach solution, applied without walking on or scrubbing the shingles, and it may come back over time.

When you replace the roof, algae-resistant shingles (which contain copper-coated granules) slow regrowth. See shingle roof replacement for product options.

Is Moss or Lichen Bad for a Roof?

Moss is less common on sunny Florida roofs, but lichen and moss do grow in heavily shaded spots and on tile. They hold moisture against the roof and their roots can lift granules or work into gaps. Trimming overhanging branches lets the roof dry out, and any removal should be gentle so the roofing underneath isn't damaged.

Why Is There Mold in My Attic?

Attic mold usually has one of two causes: a roof leak that keeps the sheathing damp, or warm, humid air trapped in an attic without enough ventilation. Signs include a musty smell, dark spots on the underside of the roof deck and damp insulation.

The roofing fix is to stop the water: repair the leak, correct the ventilation, and replace sheathing that is damaged. Cleaning up mold is a separate job. In Florida, mold remediation of more than 10 square feet must be done by a mold remediator licensed by the Department of Business and Professional Regulation, so large mold problems call for a licensed remediator alongside the roof work.

What Causes Wood Rot in a Roof?

Wood rot is fungal decay in wood that stays wet. On roofs it shows up in fascia boards behind overflowing gutters, soffits, the edges of the decking and around old leaks. Soft, crumbling or dark wood at the roof edge is the usual sign.

Rotted decking can't hold roofing fasteners securely in high wind, so it's replaced before new roofing goes on. Rotted fascia and soffit are replaced and the water source is fixed so it doesn't happen again. This is part of every roof replacement we estimate.

Can Termites or Roof Rats Damage a Roof?

Yes. Drywood termites are common in Florida and can damage roof framing and decking; small pellet-like droppings (frass) and hollow-sounding wood are typical signs. Roof rats and other wildlife get into attics through gaps at roof edges, damaged soffits and vents, and can tear insulation and chew wood.

Pest and wildlife problems are treated first by a licensed pest control or wildlife company. The roofing work comes after: replacing damaged wood and sealing the openings so animals can't get back in.

Does Salt Air Damage a Roof?

Salt isn't biological, but it is the other main contaminant on coastal roofs. On Siesta Key, Longboat Key and other waterfront areas, salt air corrodes fasteners, flashing and metal panels faster than inland. Coastal-rated fasteners and finishes, and a rinse-friendly roof design, help. See metal roof replacement for coastal metal options.

How Do You Prevent Algae, Mold and Rot?

• Trim branches that shade the roof or drop debris on it
• Keep gutters and valleys clear so water can't back up under the roof edge
• Make sure the attic is ventilated so humid air can escape
• Fix small leaks quickly, before wet wood starts to rot
• Choose algae-resistant shingles when you replace the roof
• Book a roof inspection every year or after a major storm