Your roof is designed to protect your home and your family from the elements. Heat, cold, sun, and storms all take their toll. Eventually, you may notice green clumps growing in shady places across your roof. These unsightly splotches are very likely moss.
Moss is more than just an unattractive nuisance. Over time, It can cause damage to your roof. Moss absorbs water and keeps the roofing underneath it damp. On sloped roofs, moss can intercept water draining down your shingles. If you have asphalt shingles, the moss can cause the edges to lift, which makes them more vulnerable to blowing off in high winds. It is important to know how to remove moss from a roof safely if you do find roof moss.
Why is There Growth on my Roof?
Moss and other plant or fungus growth is a very common problem for roofs, even in parts of the country that don’t see much rain. Moist, shady places are the ideal spot for moss, lichen, and algae to grow. Typically, this will be a North facing part of your roof that doesn’t get much sun. Spores can be spread by wind, birds, and bugs, and when conditions are ripe they will bloom.
Newer asphalt, fiberglass, or slate shingles may have a moss resistant chemical coating on them, but older shingle roofs are commonly invaded by moss or other growth. Even if you know how to clean your shingles regularly, moss can be found hidden in the crevices between them.
When moss is growing on a metal roof, there’s a good chance the protective coating on your metal shingles has worn off. Because moss usually grows in areas untouched by the sun, it can retain water and stay damp, which can lead to rust or corrosion.
When you’re removing large patches of moss from a metal roof, the best bet is to repaint your roof. A professional roofer has the experience to remove moss and repaint your roof safely, and they are much better at spotting signs of wood rot or leaks under your roof. It can take practice to learn how to find a roof leak and it’s best to consult a professional before attempting any patchwork on your own.
See our guide on how much is a metal roof.
Once growth is established on your roof, it can be difficult to get rid of. Despite the fact that they prefer a damp environment, moss and lichen have evolved to go months without water, so even in places like San Diego where there’s not much rain, it probably won’t clear up on its own. As moss and lichen get more established, they’ll attract a wide variety of insects and birds hunting for them. Left unchecked, other plants may start to grow in the mossy areas, and you’ll have more moisture build-up that can lead to major structural problems for your whole house.
So how do you get rid of it?
Inspect Your Roof First
It’s a good idea to have a professional roof inspection once or twice a year to keep an eye out for developing problems before they require costly repairs. If you have a sizable patch of moss on your roof, it may have already caused some damage to your roof. In some instances, it may be better to replace your roof than waste time cleaning the moss off. Take the time to check for leaks. You may be able to patch them up by replacing shingles or applying sealant. Check the attic for signs of rotting wood. Depending on the extent of the damage, you might be able to replace it without a total tear-off.
A professional roofer can check for leaks, repair or replace shingles, and reseal or replace any flashing that’s compromised. They can also quickly identify structural problems and have all the proper tools and training to safely work on your roof.
If the roof inspection shows that the structure is compromised, it’s time to replace your roof. You can use preventative measures to keep the moss from coming back on your new roof, which we’ll discuss shortly.
Removing Moss and Other Growth
If you decide to take a DIY approach to clean moss off your roof, you need to take all proper safety precautions. Use a rubber footed safety ladder, and make sure you have someone to spot you. Always wear a helmet, and never walk on the roof of your house. Roofers use a safety harness and rubber-soled boots for traction. They may also install toe boards and roof brackets if necessary. If you can’t address the problem from a ladder, you risk a severe injury that will cost a lot more than hiring a professional.
If you can reach the growth from a ladder, you can try following these steps, but be wary—there are several ways you can cause damage to your roof in the process.
1. Scrub it off
Scrubbing the roof is a delicate process and you may damage your roof. Asphalt shingles have protective oils and tar on them to protect them from UV light and moisture, and the shingle granules can be knocked off if you apply too much force. Most metal roofs have a protective coating to protect from corrosion. If you use the wrong kind of brush or scrub too hard, you can shorten the lifespan of your roof.
So how to clean your roof? When you’re cleaning your roof, it’s best to use a gentle scrub brush and to work slowly so you don’t scratch your roofing material. If you have a shingle roof, brush from top to bottom to avoid lifting the shingles.
Scrubbing the moss can also help spread the spores, and you may begin dealing with more moss growth in as little as six weeks. Additionally, bits of moss that break off can still regrow. Even the smallest bit of moss you miss with a brush can reestablish itself fairly quickly.
2. Wash your roof
Before you use any agents to kill off any remaining moss, it’s a good idea to clear the entire roof of any remaining debris that may protect the moss spores. Pressure washing your roof may seem like a simple solution to roof cleaning, but it’s a bad idea. Pressure washers can damage shingles or protective coatings and lead to leaks.
When you’re rinsing off your roof, it’s much better to use a standard spray attachment for a hose. You’ll also need to be very mindful of any water that drips down onto your ladder, which can greatly increase the risk of slipping,
3. Kill the spores
There are several sprays you can use to kill moss growth on your roof. Vinegar or a 50/50 chlorine bleach and water solution are commonly used and are very effective. Unfortunately, they are equally effective at killing other plants.
Once you rinse the spray off, any of it that lands on your landscaping may cause a lot of damage. One way to offset this is to thoroughly wet your plants before you rinse the roof to protect them from the runoff. You can also spread plastic sheeting across any sensitive plants or walkways to minimize their exposure.
Some homeowners opt to leave the sprays on the roof instead of rinsing them. Bleach and vinegar both evaporate fairly quickly, but they can still be fairly harsh on your roof and break down any protective coating.
In addition to vinegar and chlorine bleach, there are a lot of products on the market specifically formulated for moss treatment. The more eco-friendly formulas use gentle ingredients, like baking soda or zinc salts, that are less likely to destroy your lawn or contaminate water sources. These are still effective at killing the plants and fungus growing on your roof without the risk of damaging your roof.
Preventing Moss Growth
Sunshine is one of the best natural moss deterrents. Keep the trees trimmed away from your roofing system to prevent shade. This will also protect your roof from falling limbs and animals that might seek shelter in your attic.
Leaves, sticks, and other organic materials attract spores. Cleaning your roof and gutters regularly will help prevent moss spores from taking root on your roof. It’s also important that you have proper drainage on your roof to keep things dry and to maintain airflow on your roof, particularly for a cedar shake roof or other wooden shingles. Anytime there is standing water on your roof, it can lead to wood rot, mildew, mold, and leaks.
Galvanized steel roofing panels have a protective zinc coating on them to prevent corrosion. The zinc also deters plants and molds from growing on your roof. Over time, the coating can wear out or get damaged from falling debris or hail.
If you have a traditional shingle roof, you can install zinc strips along the ridges of your roof. As it rains, the water will wash down tiny specs of zinc that will kill moss or algae growth before it becomes an issue.
Leave it to the Pros
DIY roof maintenance can be dangerous, and a simple mistake can put your roof at serious risk. In many cases, damage caused by repairs you make yourself isn’t covered under home warranties or insurance. Professional roofers have the tools and training to remove moss from your roof, and in the long run it can save you a lot of money in repairs.
Preman Roofing-Solar offers a wide variety of roofing services, including inspection, routine roof maintenance, and moss removal. We’ve serviced San Diego and the surrounding areas since 1999, and all our pricing, timelines, and maintenance comes with our guarantee. Contact us today for a free estimate.