Along the roof where there is more shade from nearby trees, you may have noticed that the normally dark shingles have a green appearance. That green substance is moss. While moss may look pretty and give a more natural, woodland appearance to your home, it can actually damage the roofing system.
Moss grows in shady areas of the roof. So it is prone to appear on the northward facing part where sunlight is the weakest. Once moss begins to build up, it will start to grow under the shingles and push them upward. Thick moss will also hold in more moisture. With the roof covered in moss and shingles buckled up, the moisture can invade your home to cause rot and decay.
Remove Moss from Shingles
There are several ways to remove moss from the shingles. The method you select will depend on the state of the existing roof system, the amount of work you want to place into the task, and your budget. Also, take into account the height and architectural complexity of the roof, as you will need to use a ladder to get up high to treat the problem.
Replace the Roof
Based on the state of the roof, you may simply replace the entire roofing system. This strategy is ideal if your roof has overall damage or when the shingles have reached the end of their lifespans. If the roof is still in good shape, then you can clean the moss off using these other methods.
Prepare Foundation Plants and Roof for Cleaning
Before selecting a cleaning method, you want to wet all plants, flowers and bushes along the foundation. This makes it easier for the moss to slide off once you toss it over the roof. You can also cover over the plantings using plastic sheeting. After the cleaning, make sure to wash off the moss that may have collected on the plantings.
Scrub Off the Moss
One of the simplest, and messiest, ways to remove moss is to scrub it off. You want to wet down the moss with a garden hose. Using a soft-bristle brush, work at the top of the roof and make your way down. Gently rub the moss off the shingles without ripping and scouring the area.
If the moss is stubborn and parts of it can’t be removed with a scrub brush, you can make a homemade cleaner. Mix 2 gallons of water with one of these household cleaners: 8 ounces of mild dishwashing liquid, white distilled vinegar (1 and a half to 3 and a half cups), or 1 cup of oxygen bleach. On a cloudy day, wet down the roof and apply the cleaner. Let it sit for 40 minutes before scrubbing the roof and rinsing it off.
There are also dry and wet commercial cleaners available. Some of these cleaners can be applied without rinsing them off. Instead, the rain will mix with the cleaner and remove it as well as the moss from the shingles.
Some common types of commercial cleaners include Bayer 2-in-1 Algae and Moss Killer, Wet & Forget, and Moss B Ware. Before using any cleaner, make sure to read and follow the manufacturer’s instructions for proper application. You will want to protect your plantings and other outdoor structures before applying the commercial cleaners.
Avoid Using Power Washers
It is true that you could use a power washer to blast the moss off the roof. However, high water pressure could further damage shingles that are already chipped or worn out. The water blast can also strip off the shingle’s granules that help protect your roof from adverse weather. If you decide to use a power washer, use the lowest pressure setting and stand at the top of the roof to wash the moss downward.
Prevent Moss from Returning
Once the moss is removed, consider adding copper or zinc strips to the top ridge of the roof. These metals naturally kill off algae and moss. You should also prune tree limbs so that more sunlight can reach the shingles.