Dark Roof Streaks Cleaned Off Two Homes

Those dark streaks you see spreading across a roof aren't just a cosmetic issue. That black discoloration is almost always algae - specifically Gloeocapsa magma - and it feeds on the limestone filler in your shingles. Left alone, it holds moisture against the roof surface and slowly breaks down the granules that protect your shingles. Over time, that shortens the life of your roof.

We knocked out a couple of roof cleanings that are a good example of what we deal with regularly. One was a gray-shingled home heavily shaded by trees - perfect conditions for algae to take hold. The staining had spread across a large portion of the roof and was pretty hard to ignore. The other was a darker-shingled home with similar growth starting to show.

For both jobs, we used a soft wash approach. That means low pressure with the right cleaning solution - not a pressure washer blasting away at your shingles. High pressure can strip granules right off the surface, which is the last thing you want. Soft washing kills the algae at the root and lets the treatment do the work, not the force of the water.

The difference after a safe cleaning like this is noticeable. The shingles look uniform again, the roof reads clearly against the siding, and the overall curb appeal of the home comes back in a big way. More importantly, the biological growth is gone - not just rinsed off temporarily.

If your roof is showing dark streaks or patchy discoloration, it's worth getting it looked at sooner rather than later. Algae growth spreads, and the longer it sits, the more it works against your shingles. A proper soft wash cleaning is a fraction of the cost of a premature roof replacement.