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, voids most manufacturer warranties, and only removes the surface stain. The algae returns within months. This is the single most common and costly roof mistake we see in Austin.

Soft washing kills it at the root

The roofing industry and shingle manufacturers approve one method: soft washing. We apply a treatment that kills the algae at the root using low pressure, then let it rinse. The streaks fade, and the treatment helps keep them from coming back for years. 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.