Moss and algae are fairly common problems with most residential, asphalt roofs. Unfortunately, they grow regularly and are both unsightly on any home. Worst of all, they can damage your roof if they’re left to their own devices. That’s why it’s important to take one day out of the summer to give your roof a bit of a cleanup and figure out how you can prevent moss or algae from growing on your roof again. First, here’s a bit of info on why they’re there in the first place:


What Causes Moss and Algae Growth?


Moss and algae growth are common in humid climates like Michigan, and most often appear in shaded, cooler areas of the roof. You’ll recognize moss as little furry green spots on your roof, while algae growth looks more like dark streaks. They are both fairly common issues that can be prevented, but they can also be taken care of with a simple wash. Either way, it is important to address moss and algae growth on your roof, because if not taken care of, they can lead to more serious problems.


Since moss and algae both like moist, wet climates, they’re typically indicative of an excess of water on your roof. If allowed to stay—moss especially—they can lead to the rotting of your sub-roofing, damage to your shingles, and larger-scale water damage that’s hard to take care of. There are a few ways to prevent them, but they take a bit of work:


Preventing Moss and Algae Growth


Moss – Moss thrives in dark areas, where it’s cool and water can collect. Typically, trees are to blame for most moss growth. If you have trees with limbs that hang over your roof, they drip water after it rains, and they shade your roof. This creates the perfect environment for moss to grow. If you want to prevent moss as best possible, consider at least taking down branches over your roof, if not cutting down the trees that are very close to your house.


Algae – Algae is trickier than moss to prevent, but some shingle manufacturers are making strides with copper composite shingles. Though these shingles do cost more, they contain copper particulate, which is toxic to algae. If re-roofing your home with new shingles sounds like too much work, it’s good to know that metal strips can do more or less the same job. If you have metal flashing around your chimney, you’ve probably noticed less algae on those parts of your roof. That’s because when it rains, metal particulate from that flashing is distributed down your roof, killing algae as it goes. One solution to algae growth is to attach metal strips on either side of your roof, just below the ridge. Metal particulate washing down will help kill algae.


Getting Rid of Algae or Moss


If you already have algae or moss, and you’re looking to get rid of it, it’s good to know that the process isn’t that difficult. It’s really just a matter of getting a soft roof brush, some cleaning solution, and a ladder, and getting to it. Check out these steps:


1. Rinse the Roof

Rinse your roof first with plain water from the hose. Don’t use a pressure washer— that’s too hard on shingles and can damage your roof. Rinsing will get rid of some initial moss and algae and will help any plants you have growing down below resist chemicals you use later on.


2. Choose your Solution

There are a number of roof cleaning solutions out there, you just need to pick one. Wet & Forget and Roof Wash are both popular, or you could make your own solution out of a 1:1 ratio of bleach and water. Simply pick one area at the top of your roof, and apply your chosen solution.


3. Scrub Gently

After you’ve applied your washing solution, take your roof brush and gently scrub one small area at a time, working down the roof. This helps to ensure you don’t break, crack or pry up any shingles. Work in small areas at a time, so you don’t waste solution, and you don’t forget your spot.


4. Rinse

Finally, once you’ve scrubbed the whole roof, simply rinse it down with clean water— again, not with a pressure washer—and let it dry! It’s good to pick a sunny day to do this project, so your roof can dry quickly, and you can make sure you got all the moss and algae off.



Moss and algae on your roof are an issue, but they’re fairly easily solved. Just one wash a year will typically keep most moss and algae from making a home of your roof. If you’re having concerns about washing your own roof for moss and algae removal, or you’d like a bit of help with the project, don’t hesitate to call Werner Roofing. Local, trusted roofing experts, we’ve been helping families in West Michigan repair and tidy up their roofs for decades. Whether you need help choosing a roof wash solution, or you’d like us to take care of the wash itself, we’re happy to help. Give our office a call at 616-844-5382 or contact us online today for a free roofing estimate!

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