How to Prevent Moss From Growing On the Roof

Moss and algae can do considerable damage if they’re left for too long. Both use the combination of moisture and organic materials – aka your roofing materials – to grow and colonize. As a result, structural materials begin to rot and decay, leading to expensive, long-term damage.

Tips For Preventing Moss & Algae From Growing on Your Roof

The following tips can help you keep moss and algae from taking up residence on your roof.

Eliminate Moss & Algae ASAP. If you already see green and/or blackish growths on your roof, it’s important to remove them as soon as you can. In the right conditions, mold can grow pretty fast and this growth directly relates to the rate at which roofing materials decay. Established moss growths can be manually removed. Then, a thorough wash and the application of a bleach-water solution can be applied to remove the rest.

Moss growing on roof
How do you prevent moss from growing on your roof?

Unless you’re familiar with ladder- and roof-safety, professional moss and algae removal is often the safest and most efficient way to eliminate these offenders from your roof.

Trim Overgrown Tree Branches. Moss and algae require a moist environment. This is why we typically see the largest infestations accumulating in the shady areas created by overgrown tree limbs. Hire a certified arborist or professional tree trimmer to keep mature tree branches in check. Trimming them back and away from your roofline will help prevent moss and algae on the roof and will also prevent roof damage from fallen limbs and branches.

Keep Gutters & Downspouts Clean & Clear. When gutters and downspouts are full of debris, water has the chance to accumulate for extended periods. During the rainy season, this can lead to days or weeks of overflow, causing water to spill over and soak into roof and eaves materials. As long as temperatures are warm enough (about 35°F to 80°F), the ever-present moisture provides a perfect environment for moss to settle in.

Inspect gutters and downspouts at least twice a year to remove debris and make sure water is flowing through them as designed. Clear any clogs immediately to prevent water damage and repair any rusted, split or corroded gutter/downspout runs as soon as you can.

Use Strips of Zinc Flashing. Remember we said that moss and algae use organic materials as a food source? Thin strips of zinc flashing (copper and lead flashing work as well) can be installed underneath rows of shingles where moss and algae are the most prevalent. Clean the roof first to eliminate any current moss or algae. Then, apply the strips as per the manufacturer’s directions. Always contact your roofing manufacturer and apply the strips as per their instructions to avoid violating your warranty.

Always use a safe ladder and climbing practices while performing work on a roof. If this is not your area of expertise, hire a professional roof cleaner or roofing contractor to do the work for you.

Need the help of a professional to clean your roof, gutters, and/or downspouts and/or to prevent future moss and algae growth? Contact Proman WC at 425-908-9121 or 510-478-4880. Don’t forget to ask us about our 15% discount for new customers.

Is That Moss Up On My Roof?

Green roofs are trending these days. However, there is one thing worth noting: green roofs should be designed that way. If you’re waxing poetic as you gaze up at your own green roof, one that has become green over time as the result of moss and algae growth, it’s time to halt the Irish soundtrack and check back into reality.

Yes, That Probably IS Moss Up On Your Roof

Moss and algae may lend a lovely green hue to your roof, and give your home a romantic, cottage-like look but, in fact, they’re bad news. Moss is a sign that:

  • The roof is laden with moisture.
  • Organic materials are being consumed for its growing pleasure.
  • Significant structural damage might be taking place right under (or over) your nose.

Contrary to what you may have learned, moss doesn’t just grow on the “northern” side of things. In fact, moss grows:

  • Where it’s wet. Moss likes a wet and shady environment. If things get too dry, moss will go dormant or die off. However, moss also helps to keep things wet, so where moss grows, moisture damage or rot can ensue. In the case of your roof, this can lead to moisture penetration that seeps into your attic and interior wall spaces.

    Is That Moss Up On My Roof?
    Remove Moss From Your Roof as Soon as Possible
  • Where it’s shady. Moss isn’t a huge fan of direct sunlight. A little light is fine but it prefers more dappled or diffused light. This is why it tends to grow on areas of your roof that are shadowed by a mature tree or neighboring buildings.
  • Where it’s cool. We all have our “preferred” temperatures, and moss is no exception. Typically, moss likes to grow in temperatures between about 20° F (although they prefer it a little warmer) and 70° F. This is why moss growth on roofs tends to peak during later winter and spring months, or into a cooler summer.

Remove Moss From Your Roof as Soon as Possible

Moss removal is key to protecting the health of your roof and your home. It’s feeding on the organic matter found on your roof, namely your shingles. Thus, over time, the moss can actually rot away your roofing materials, which leads to expensive roof repairs and replacement.

You can remove moss on your own, by climbing on the roof and scraping it away. Then, you can spray a 50:50 mix of water and bleach to keep the spores from growing back. Don’t use a pressure washer for this as it can damage the shingles and/or spray water in between roofing materials, which can also result in water damage.

Keep in mind that a roof with moss will be wet and slick. There’s a good chance algae and mold are also present, which makes for even more slippery conditions. Always make safety your first priority.

If mold growth seems excessive, it may be worth it to hire a professional. Proman WC has provided professional roof moss removal services to our bay area clients for 10-years and counting. We’re happy to come out and take a look and will provide a free, onsite quote. Contact us today by calling 425-908-9121 or 510-478-4880. You can also email us at

Is Moss Bad For My Roof?

An abundance of rainfall and year-round moisture is one of the many benefits of living in the Northwest. The downfall is that pervasive moisture can lead to the growth of things like mold, mildew and moss on and in the infrastructure of your home.

All three are detrimental to your home’s structural health and moss, which loves to grow in the shingles of rooftops, is one of the most damaging.

Moss Growth on the Roof Causes Irreversible Structural Damage

Moss is a type of plant, called a simple plant, that doesn’t grow any flowers. Typically, you see moss growing in moist, natural environments, like along streambeds, in fallen logs, rotting sections of trees or even in rocks that have enough decomposed matter to create an anchor for the moss’s root beds. It’s a beautiful plant and it adds a forest-esque charm to all it blankets. However, don’t be fooled by its charm if you notice it on your roof.

Is Moss Bad For My Roof?
Is Moss Bad For My Roof?

Moss likes areas that are damp and shaded. It absorbs the moisture from the environment like a sponge, and decomposes the organic substance it’s chosen as its home in order to suck up nutrients. If you notice moss growing on your roof, you are watching your roof’s decomposition in action. Once the organic roofing materials have been infiltrated, the decomposition of their structure will make your roof less waterproof and more vulnerable to further moisture and other environmental damage.

If left long enough, your home will begin wicking this moisture in, allowing mold and mildew spores to take up residence there as well. The combination of moss, mold and mildew is devastating to wood and drywall structures. It can lead to thousands of dollars of damage – if not an entire roof replacement – as well as the repair of any attic, wall or interior crawl or wall spaces that may have been compromised as well.

Moss-Covered Roofs are Dangerous

Moss-covered roofs are also dangerous. First, they are dangerous for anyone who is working up on the roof because the moisture, moss and potential mold and mildew make a roof’s surface more slippery than it already is. If the damage has been left too long, sections of roof can cave in, posing further danger to the building’s occupants or the possessions you have stored inside.

Treat Moss Roof Problems ASAP

If you notice moss growing on your roof, it’s important to act sooner, rather than later. Like any new plant that is establishing itself in a new environment, moss is easiest to remove when it is just getting started than it is when it has taken up residence for a year or two. And, of course, the longer it has been there, the more damage it may have caused.

While moss can be removed by DIYers using a garden hose and hand-scraping, the job is best left to the professionals. Many homeowners try to use a pressure washer on their own, which can do further damage to the roof and the home’s structure. Pressure washing a roof should only be done by professionals who know exactly what they are doing.

Plus, as mentioned above, established moss makes for a very slippery environment and a professional moss removal crew will have the proper protective clothing and fall-protection equipment to make sure the moss is removed safely.

Have you noticed moss growing on your roof? Do you have a moss colony that has been there for years? Contact Proman WC and schedule our crew to remove the moss safely and efficiently. Call 425-908-9121 or 510-478-4880