If your roof has dark streaks running down it, you're not looking at dirt or age — you're looking at Gloeocapsa magma, a blue-green algae that thrives in Florida's heat and humidity and feeds on the limestone filler in asphalt shingles.
Why it matters
Left alone, the algae holds moisture against the roof, degrades shingles faster, and can shave years off the roof's life. It also drives up cooling costs by darkening the surface. It won't wash off in the rain, and it spreads.
Why you can't just pressure wash it
High pressure strips the protective granules off shingles and can crack tile — trading an algae problem for an expensive roof-replacement problem. Most shingle manufacturers actually void warranties over pressure washing.
The right fix
A no-pressure soft wash with the correct treatment kills the algae at the root and lifts the streaks without touching the granules. The roof looks new again, and the treatment keeps it clear far longer than a rinse ever could.