Do you ever notice black stuff growing on some of the shingles on your roof? Your first thought is likely “What is that? Is it Mold, mildew or soil that somehow made its way up there?” You also my wonder do you need to clean your roof?

So it is likely, that the black unidentifiable sludge is algae. Algae tends to grows on roofs in areas where water or moisture collect. The mold spores reach the roof by a combination of birds and wind.

You also might see green fuzzy areas on your roof, and this is most likely moss growing on your roof. This is typically caused by shade and moisture as they create an ideal habitat for moss growth.

So what should you do if you see moss or algae on your roof? Is roof cleaning necessary, or should you leave it alone?

One reason to clean your roof is to extend the life of your shingles or other roofing material. Algae isn’t harmful to asphalt shingles,  but moss is. Moss can make the edges of the shingles curl upward, making them more likely to blow off the roof during windy weather.

Although algae won’t harm your shingles, it can negatively affect their performance. That’s particularly true if you have a reflective or cool roof. Black algae growth will interfere with the reflective properties of the roof.


During roof cleaning, the focus is on killing and removing the algae or moss growth. Chlorine bleach, the same kind you use to whiten laundry or scrub your toilet, is enough to kill off moss and algae spores. It is recommended to have a 1:1 ratio of bleach to water to clean a roof. They also advise against using a pressure washer on asphalt shingles, as the force of the water can damage them.

After being allowed to sit on the roof surface for up to 20 minutes, the bleach solution should be rinsed away with clean water. A few rain showers should be enough to wash any remaining algae off the roof. The person cleaning your roof might also use a leaf blower to remove any leftover pieces of moss.

Contact Us Today

The next time you’re searching for roofing companies near me, roofing contractors near me or roofing contractors ct, or roof replacement near me look no further then BP Builders. We would be happy to fix the problem. Call us now or fill out the form on this page. BP Builders is a full-service company offering complete roofing, siding and gutter replacement services. For prompt, friendly and professional help, please contact us today!