What are the Black Streaks on my Roof?

What are the black streaks on my roof? Have you ever asked yourself that question? What are they? Does it mean you need a roof replacement? You pull in your driveway after work and are greeted with that ugly, dirty looking, black roof. It can be stressful and you may be asking yourself what’s happening and how can you fix it.

If these are questions that you’ve asked yourself or maybe have caused anxiety for you (because a roof replacement is expensive), I’ve got some good news: in most cases your roof does not need to be replaced, it only needs to be cleaned.

So.. what ARE those black streaks?

In short, those black streaks are called Gloeocapsa Magma. It’s actually a form of algae that feeds on the limestone filler used in the creation of asphalt shingles. If left untreated, these unsightly black streaks can cause the premature degradation of your shingles. So early treatment can help add years to your roof. But even if your roof is completely black with stuff, it’s not too late to treat it.

In most cases, a roof cleaning is all you need. Replacement is often unnecessary (sorry, roofer friends) and expensive. A roof cleaning will cost a fraction of the cost of a replacement. In a previous blog post, I answer the question of if you need a roof replacement or just a roof cleaning. To read that, click here: https://www.hogwashpressurewashing.com/blog/2016/12/2/roof-cleaning-or-roof-replacment

How do you clean it without damaging my roof?

Great question! Don’t ever use, or let anyone use a pressure washer on your roof. No pressure washer of any kind! Even a low psi pressure washer is dangerous to operate, can damage the shingles, remove granules AND void any warranty you may have.

So the answer is - calling Hogwash Pressure Washing. We have a dedicated roof cleaning system that only puts out about 40-60 psi (less than a garden hose) and allows us to apply a specially formulated, roof cleaning mix that will safely kill the bacteria and algae (and moss and lichen too) on your roof WITHOUT damaging pressure and without voiding your warranty.

Our roof cleaning process...

  • ...is recommended by the Asphalt Roofing Manufacturers Association. You can read their recommendations by clicking here (www.asphaltroofing.org/roofing-professionals/resources/technical-bulletins).

  • ...will not void your warranty! (Using a pressure washer or high pressure equipment will)

  • ...is custom suited to your needs! We utilize specifically blended cleaning solutions designed to clean your roofing material (Asphalt, Slate, Tile, etc.).

  • ...will extend the lifespan of your roof by killing the mold, algae, lichen and other infestations that take root and work to destroy your roof.

  • ...will significantly enhance the curb appeal and beauty of your home. You have worked hard to make your house a home; let us help you make it shine!


Here’s a couple photos of recent roof cleaning we did in the country club area of High Point, NC. The good news is we do roof cleaning all over NC, especially in Greensboro, Winston Salem, Salisbury, Lexington, Asheboro and High Point.

high point, nc, roof cleaning - before

high point, nc, roof cleaning - before

high point, nc, roof cleaning - after

high point, nc, roof cleaning - after

Click here to watch a short video of this job.

So save money - don't replace your roof if it doesn't need it.  Call us today and we can come out and see if your roof is a candidate for our roof cleaning process.  336-918-8856, or go online at: https://www.hogwashpressurewashing.com/contact.

Thanks for reading!

-Hogwash Pressure Washing