Why Austin Roofs Get Black Streaks (and How to Remove Them)

Drive through almost any Austin neighborhood and you will see roofs with dark streaks running down the shingles. That is not dirt and it will not wash off in the rain. It is a hardy blue-green algae called Gloeocapsa Magma, and Austin's heat and humidity are perfect for it.

What causes the black streaks?

Modern asphalt shingles contain limestone filler. Gloeocapsa Magma feeds on it, spreads spore to spore, and leaves the dark streaks you see. Once it takes hold it keeps growing, holding heat against your roof and shortening shingle life.

Never pressure wash a roof

High pressure blasts the protective granules off your shingles, shortens the life of the roof, and only removes the surface stain. The algae itself stays behind and grows back. This is the single most common and costly roof mistake we see in Austin.

Soft washing kills it at the root

Shingles need low pressure. We apply a treatment that kills the algae at the root, then let it rinse off gently, so the protective granules stay on the roof. The streaks fade, and because the algae is treated rather than just rinsed, it grows back much more slowly. See how our roof washing service works.

How often should Austin roofs be cleaned?

Most Austin roofs benefit from a soft wash every two to three years, sooner on north-facing slopes and under heavy tree cover. Catching it early protects the shingles and your curb appeal. Get a free instant estimate for your roof in 30 seconds.