Al and Cal Homes and Community: Removing Black Stains on Roofs

Removing Black Stains on Roofs

A client of mine gave me a call today concerned about the stains on their otherwise perfectly fine but  roof.   I remembered reading Reuben Saltzman's blog on the subject and forwarded it over to them.    I thought other Sellers and Buyers might find his informative post helpful as well.   

If you have nasty black stains on your asphalt shingle roof, don't worry.  The black staining won't damage the shingles, and it won't make your roof leak.  This black staining is typically caused by an algae, and usually shows up on areas of the roof that don't get much sunlight, such as the north side.

Black roof stains

Garden SprayerIf you don't like the look of these stains, you can clean your roof with some basic supplies that you probably already have at home.  Simply mix up a solution of two parts water to one part bleach in a garden sprayer.  Spray down the affected areas of your roof with this solution, let the solution soak for about ten minutes, and then  spray the cleaning solution off your roof with a garden hose.

For this blog, I started by cleaning a small section of the roof and letting the shingles dry, just to get a good photo showing how effective this is.

Black roof stains cleaned

A few precautions:

  • Protect your lungs.  Bleach is nasty stuff, and you'll get it in the air when you spray it with the garden sprayer.  Wear a respirator.
  • Watch where you spray the cleaning solution.  The solution won't harm your shingles, but you could certainly do damage to other surfaces or people if you're not careful.
  • Wear grubby clothes.  If you get this solution on your clothes, you'll ruin 'em.
  • Protect your vegetation.  If the cleaning solution will run off the roof on to your plants, you should cover them up with tarps or something similar.
  • Be careful on a ladder, and don't walk on the roof.  This is 'no-duh' advice, but I'm saying it anyways.  Even if you're used to walking on your roof, it will get very slippery once the bleach interacts with the algae, and you could easily slide off the roof.
Some people get whipped up over the topic of bleach.  If you don't like the idea of using bleach, you could buy a product made for cleaning roofs, such as RoofOX 3000.  I've heard good reviews, but never tried this stuff personally.

Reuben Saltzman, Structure Tech Home Inspections - Email - Minneapolis Home Inspector


Carol-Ann Palmieri

Al and Cal Realty Group

Remax Executive Realty




Comment balloon 8 commentsCarol-Ann Palmieri • November 28 2011 07:17PM


Good information to have just in case this  roof problem happens to someone I know. Now I will know what to tell them. Thanks for sharing.

Posted by Carlotta Remong (Berkshire Hathaway HS N.E. Prime Properties) over 7 years ago

Hi Carlotta.   Thanks for reading.    I remembered Reuben's blog and when it came up real time with me, just had to share it again!  

Posted by Carol-Ann Palmieri, "Cal" the Real Estate Gal (RE/MAX Executive Realty, Al and Cal Realty Group) over 7 years ago

What a great post. Thanks for reblogging it. I've bookmarked it for future reference.

Posted by Chiara Petro, Your KEY to Home Sweet Home - Knoxville TN (eXp Realty - Angie Cody Team) over 7 years ago

Good re blog Cal, the bleach solution is a great tip and the safety tip are very important.

Posted by Al Raymondi, Ormond By The Sea Florida - Home and Condo Sales (Ocean View Realty Group in Ormond By The Sea Florida) over 7 years ago

Hi Cal Gal - this is an important issue regarding roof cleaning. I would also add that it's important not to let the solution run into storm drains - with that said, we have somebody else clean the section of our shady roof  - we have a very high and steep roof line, not worth the risk.

Posted by Debb Janes EcoBroker and Bernie Stea JD, REALTORS® in Clark County, WA (ViewHomes of Clark County - Nature As Neighbors) over 7 years ago

Carol Ann,

Excellent re-blog. Stained roofs look old and buyers are always leery.

I have looked every day for a blog by you to comment on and this is the first one (re-blog) in several days. I hope you are busy with deals!


Posted by Robert Bob Gilbert, Your Katy TX ( West of Houston) Real Estate Expert (Berkshire Hathaway HomeServices Anderson Properties) over 7 years ago

Hi Chiara.   Thanks for checking it out.   Reuben has some great info.


Hi Al.   Thanks.   Safety first!  


Hi Debb.      Didn't think of that, but you are 100% right on.   


Hi Bob.    Thanks for checking in.    It's been beautiful here for late November and I have been trying to take advantage of the "outdoors" before it comes to a quick hault.     


Posted by Carol-Ann Palmieri, "Cal" the Real Estate Gal (RE/MAX Executive Realty, Al and Cal Realty Group) over 7 years ago

Stained roofs can be such an eyesore, and this souds like such a terrific solution to the problem!

Posted by Lawrence "Larry" & Sheila Agranoff. Cell: 631-805-4400, Long Island Home and Condo Specialists (The Top Team @ Charles Rutenberg Realty 255 Executive Dr, Plainview NY 11803) over 7 years ago