What are the black streaks on a Florida roof?
They are a cyanobacteria called Gloeocapsa magma, and it feeds on the limestone filler in asphalt shingles. That is why the streaks run downward: the colony spreads with the water.
It is not cosmetic. A colonised roof holds moisture and reflects less heat, and the organism is consuming part of what the shingle is made of. Left alone through several Gulf Coast summers it measurably shortens the life of the roof.
Why a roof must never be pressure washed
The granules on an asphalt shingle are what protect the asphalt from ultraviolet light. They are held on by nothing more than the asphalt itself. High pressure removes them, and once they are in the gutter the roof is ageing at a rate no cleaning can undo.
It also drives water up under the shingle course, against the direction the roof was designed to shed it. A pressure-washed roof can leak within one storm season and the cause is almost never traced back to the cleaning.
How often do roofs need cleaning here?
About every 24 months across most of Northwest Florida. Shaded roofs under mature oaks — a lot of Niceville and inland Pensacola — go closer to 18 months. Roofs in full sun with good airflow stretch past 30.
Many communities in Destin, Santa Rosa Beach and Panama City Beach write roof appearance into their covenants, so for a lot of owners the schedule is set by the association rather than by the shingle.
What is included
Every roof we clean gets the same four things, and the last one is the one associations ask for:
- Pre-wetting and rinsing all landscaping below every elevation treated
- Low-pressure application, dwell time, and a controlled rinse
- Gutter exteriors cleaned in the same visit
- Before and after photographs, which is what an HOA actually wants to see
How long does a roof clean take, and when do the streaks go?
A single-storey roof is usually 2 to 3 hours including the landscaping prep; a two-storey with dormers runs 4 to 5. The application itself is the short part — the solution needs 10 to 15 minutes of dwell time on each section before the rinse, and rushing that is what leaves a roof looking patchy from the street.
The streaks do not all disappear the same day. The colony dies within the hour, but the dead staining lifts progressively over the following 5 to 10 days as rain and sun break it down. A company that promises a perfect roof the moment the van leaves is either using far too much pressure or has not cleaned many roofs.
Gutters are done in the same visit. There is no sense cleaning a roof and leaving the streaks that run down the gutter face directly under it.