Does your roof have unsightly black stains on it? If so, you might understandably assume that you have a bad case of roof mold.
Actually, the dark streaks and stains that often pop up on roofs are caused by algae that are bluish-green in color – its official scientific name is Gloeocapsa Magma. Even though it’s not toxic, roof algae can harm shingles and can get into the roof deck, leading to wood rot. Algae that grows on roofs attract moisture, which will likely lead to mold growth, which is potentially harmful to both people and pets.
This type of algae growth is fairly common in areas of the country that have warm and humid summer months. They also love to hang out on roofs that have a pretty good source of shade and dew – this is why it’s so commonly seen on sections of roofs that are under trees. The tiny algae spores end up on the roof thanks to both birds and the wind; once on the roof, the algae will start snacking on the calcium carbonate found in asphalt shingles. It spreads pretty easily, too – so if you have a dark streaked roof, chances are your neighbor will get one too, and vice versa.
When you notice that your roof is looking dark and dingy in places, you definitely want to take steps to get rid of it. For DIY’ers who want to tackle cleaning their roofs on their own, you can try gently washing your roof with a spray washer filled with half water and half bleach. Please note: this is not the time to break out the power washer! Even though it might be tempting to do so – using a lot of water pressure will just end up damaging the shingles. Then, once you are finished washing the roof, be sure to rinse everything really well with plain water to remove any traces of the bleach.
Another anti-algae recipe DIY’ers can try involves mixing one cup of trisodium phosphate, one gallon of bleach, and five gallons of water – apply it to the roof and let it sit for about 20 minutes, before gently washing it all off.
For homeowners who do not wish to tackle cleaning their roofs on their own, we are happy to help them out. At New England Remediation Services, we use an algaecide specially formulated to kill roof algae and prevent it from coming back.
