What Those Dark Stains on Your Roof Really Mean
Have you looked up at your roof lately and seen dark streaks or black patches? You are not alone. Roofs all over the Hillsboro area get them. The good news: it is common and it can be dealt with. The bad news: if you ignore it, it can shorten your roof's life.
What is that dark stuff?
Those black streaks are a kind of growth that loves damp, shady roofs. Think of it as a cousin of moss. It feeds on the surface of your shingles and spreads in thin, dark lines, usually running down from the top of the roof.
You will also see thicker green moss in the shadiest spots, and sometimes both at once. Our wet Oregon winters give all of it the water and shade it needs to grow.
Is it just ugly, or is it a real problem?
A little is mostly a looks problem. But left alone, it causes real harm:
- It holds moisture against your shingles.
- That trapped water wears the shingles down faster.
- It can spread and get worse every wet season.
So while a few streaks will not ruin your roof overnight, they are a sign your roof is staying damp, and a damp roof does not last as long as a dry one.
Why the north side is always worse
Take a look and you will probably notice one side of your roof is darker than the other. That is the side that gets the least sun. Less sun means it stays wet longer, and that is exactly what the growth wants. South-facing slopes dry out in the sun and stay cleaner.
How to get rid of it
Same rule as moss: do not pressure wash it. Blasting your roof with high pressure strips the protective grains off your shingles and can do more damage than the stains ever would.
The safe way is a gentle, roof-safe treatment that kills the growth, followed by a careful rinse. A good treatment also slows down how fast it comes back. This is part of our regular roof maintenance service.
Do not forget to check inside
Dark growth on the outside of your roof is one thing. Dark growth in your attic is another, and it usually means a leak. If you see black patches on the wood inside your attic, water is getting in. Read our guide on roof leaks in the attic to learn the warning signs.
The bottom line
Dark stains on your roof are a heads-up, not an emergency. They tell you your roof is staying damp and could use some care. Want to know if yours needs a cleaning or a closer look? Reach out for a free, no-pressure inspection. We will give you a straight answer.
Talk to Sealed Roofing
Questions about your roofing job? We serve Hillsboro and the surrounding area with honest, upfront advice.
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