Greenery overhead should be limited to leaves flushing out tree canopies. If mossy foliage is carpeting your roof, it's time to get cleaning.
Moss grows in areas untouched by sun, so it can develop at a speedy pace on tree-shaded and north-facing roofs. Spreading moss can quickly upholster roof surfaces, filling in voids between shingles and tiles and reaching under and lifting up roofing materials. This heaving of shingles allows rainwater and other moisture to seep into a roof's structure to cause decay and rot.
Before you clean moss off a roof, you'll need to consider how you want to kill the plants and then remove the dead layers of moss. Later, you'll need to put some defensive measures into play to prevent moss on roof from gaining future toeholds.
Experts recommend that you save roof moss removal for a cloudy day; roof-cleaning products, which should be left to absorb into the moss for at least 20 minutes, will not evaporate as quickly as they would on sunny days. Moss can be removed physically (with water and a stiff brush on a pole or a scrub brush), chemically, or a bit of both. Use the least-toxic moss killer; chemical solutions can adversely affect the environment, as well as damage foundation plantings growing beneath roof overhangs. If you decide to use a bleach solution or other readymade roof moss treatment, protect nearby plants with plastic sheeting. You may also want to hose down the plants, shrubs, and small trees with water—the coating of water will dilute chemicals spilling downward from roof eaves.
Here are a few moss-removal solutions you can buy or create yourself.
Roof Moss Treatments
Some readymade cleaners—like Wet and Forget Liquid Mold Remover—can be mixed and applied per manufacturer's instructions and left to kill the moss with no rinsing required. Others, like Bayer's Advanced Moss and Algae, are available in ready-to-go sprays that hook up to your hose. Be sure to follow the mixing and application recommendations to ensure your safety and protect roof tiles, shingles, and plantings from damage.
You can also make your own roof-moss removers—which are generally less toxic than their chemical counterparts. Chlorine bleach removes mosses, fungi, and mildew, but it may damage plants, so dilute it before spraying on your roof. A good formula? Mix 1 quart bleach with 1 gallon water and ¼ cup of heavy-duty cleaner like trisodium phosphate (don't use ammonia-based cleaners because they create toxic fumes when mixed with bleach).
Or, make a plant-friendlier solution of 1 cup oxygen bleach and 1 gallon of water. Home improvement expert Bob Vila says you can also mix 8 ounces of Dawn dish liquid or 1½ to 3½ cups of white distilled vinegar with 2 gallons of water. Pour solutions into a pump garden-style sprayer; choose a backpack-type sprayer, which will be safer to use if you're climbing and standing on a ladder.
Once you've decided on your moss-removing solution, it's time to get started. Follow these step-by-step instructions to rid your roof of moss and any other debris that's accumulated atop your house!
Removing Moss from Roof Tiles
Learn how to remove moss from rooftops with our easy instructions. Here's what you'll need:
- Safety glasses or goggles
- Rubber gloves
- Safety rope
- Work clothes, a cap to protect your hair, and slip-resistant footwear
- Garden hose equipped with a spray nozzle
- Moss-remover of choice
- Backpack-style garden pump sprayer or a large spray bottle
- Scrub brush
- Long-handled soft-bristle brush
- Power washer (optional, see note)
- No matter which method you choose, you're going to get dirty, so dress appropriately! Wear old clothes, safety glasses, rubber gloves, a cap, and slip-resistant shoes. Have a safety rope or harness handy if you're headed to the roof's peak.
- Cover nearby plantings with plastic sheeting. Set a ladder securely in place, grab the hose, and start climbing.
- Spray all moss-covered sections of the roof with water. Always work from the top of the roof downward to ensure water pours off the roof and so the water or tools won't lift and break shingles and tiles.
- Before applying a moss-remover cleaner, use a scrub brush or a long-handled soft-bristle brush to gently scrape or pluck moss from the roof shingles or tiles. Work on one small section at a time, which allows you better control of the brush and your scrubbing motions. Move the brushes downward to protect the shingles from breakage.
- Still need a chemical solution? Use a pump sprayer or large spray bottle to apply your preferred moss-remover to the moss. Soak the moss and let the solution set per the manufacturer instructions. Using a homemade remover? Let it set for about 20 minutes.
- Grab the hose, climb up the ladder, and rinse off the moss-remover solution and now-dead moss. Remove remaining moss with a scrub brush, and rinse the roof again.
- Alternatively, you can use a power washer to clean away moss, but there are several caveats to consider. First, you need to ensure that roof shingles and tiles are not broken, chipped, or damaged, as water applied at a high-pressure is likely to amplify the damage and seep through any cracks. Also, when using a power washer, you will need to stand on the roof above the mold so you can point the power washer in a downward direction. If you opt for a power-washer method, use the washer on the lowest pressure setting possible.
Prevent Moss from Returning
Happily, there are preventive measures you can use to keep your roof moss free. First, let the sunshine in! Trim branches overhanging your roof, keep gutters free of debris, and regularly remove moisture collectors, such as leaves, branches, and seedpods, that pile up on the roof and encourage moss to grow. The best long-term solution? Attach strips of zinc (Z-Stop) or zinc-coated metal flashing strips just below a roof's peak or ridge caps; when it rains, water flows over the metal strips leaching out moss-retardant zinc particles, which attach to roof shingles and/or tiles to stop new moss from forming.
Working safe, smart, and strategically guarantees your moss-removal operations will run smoothly; these prevention measures mean you'll be able to stay off the ladder and roof for seasons, if not years, to come.