Is Moss Growing on Your Roof? Learn Why It Happens and How to Prevent It

Scott Dylan Westerlund
Reviewed by Ami Feller
Updated August 1, 2022
Moss covered house roof
Photo: tunart / Getty Images

Highlights

  • Moss likes to grow under shingles, so it’s hard to spot it from the ground.

  • Moisture and debris help breed moss growth.

  • You can prevent roof moss with route cleanings and inspections. 

  • Professional roof cleaners can help you stop moss growth for good.

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The look of moss on the outside of your home can be charming, but it can lead to problems if it ends up on your roof.  Let’s explore why moss is growing on your roof, what to do about it, and how to prevent it—for good.

Why Does Moss Grow on Roofs?

Water and debris increase your chances for moss growth on your roof. Moss will also thrive if your roof is in a shady area, because the shade stops moisture from evaporating. 

Add nearby trees to the equation, and you’ve got a haven for roof moss. That’s due to the leaves and twigs that may land on your roof and feed moss growth. But there are a few ways to address this problem—and you should, because if left untreated, moss can damage your roof.

How to Spot Moss on Your Roof 

First, you should find out if moss is hiding on your roof. It's not always easy to spot it from the ground. While moss is sometimes visible from below, it usually grows under your roof shingles. That's because the moisture that allows moss to thrive is usually trapped under the shingles, where it can flourish away from the sun’s rays.

Keep in mind that moss often grows with algae, fungus, and lichen. Here's a quick guide to what you may be seeing:

  • Moss and Fungus: Green, spongy clumps

  • Algae: Green and black streaks

  • Lichen: Grey, orange, white, or yellow flat spots smaller than the size of a quarter

To be sure moss isn’t growing on your roof, it’s best to call in a professional roof cleaner to inspect it up close. 

How to Remove Moss From a Roof in 4 Steps

Here’s how to remove moss from your roof in four simple steps.

1. Spray Off Loose Moss With a Hose

While wearing slip-resistant shoes, rubber gloves, and eye protection, carefully climb a ladder near the mossy area of your roof. Using a hose set to a low- to medium-pressure stream, spray the moss at a downward angle to blast off any loose moss. Don’t use a pressure washer, as the stream could damage your roof.

2. Brush Wet Moss With Soft-Bristle Scrub Brush

Next, use a long-handled soft-bristle scrub brush to carefully scrape the wet moss downwards toward the edge of your roof. Be sure to brush gently and in a downward motion to protect your shingles from lifting up.

3. Scrub With Cleaning Solution

Now you can apply a cleaning solution to the roof moss. You can either buy a cleaning product from a store or online retailer, or make one yourself out of dish soap and warm water. You can also use a 1/2 cup of oxygen bleach mixed with four gallons of warm water. Use a soft-bristle brush to gently scrub away at the soapy moss. The moss should pull up; just brush it downward toward the end of your roof.

4. Rinse With Hose

Finally, you can rinse the surface of your roof using your hose, on low-to-medium pressure. You may need to use your brush a little here, to help remove stubborn moss patches. Give it a final once over with the hose, and you’re all set.

What Are the Benefits of Removing and Preventing Roof Moss?

Removing and preventing moss on your roof can help protect your roof from damage. Moss compromises the protective coating on your shingles, leaving them vulnerable to warping and cracking that reduces your roof’s lifespan.

Next, allowing moss to stay on your roof means that it’s soaking up moisture every time it rains. As a result, the moss is able to spread across your roof to compromise even more shingles. However, the problem of needing to replace your roof sooner than expected isn't even the biggest problem caused by moss.

All of the moisture that's sucked up by moss can actually end up causing rot inside your home. Unfortunately, what starts off as a small patch of moss can result in expensive home repairs if the problem isn't discovered in time. That’s why it’s essential to stay on top of any moss growth on your roof.

How Do You Prevent Moss Growth?

Man spraying roof treatment
Photo: Bill Oxford / Getty Images

Good roof hygiene is essential for preventing moss growth. Make plans to keep your roof clean by removing buildup and debris seasonally. If your home is heavily shaded by trees, consider checking your roof more frequently. A good anti-moss checklist includes:

  • Routinely remove leaves, twigs, branches, and other forms of debris from your roof.

  • Look for puncture marks, broken shingles, or cracked tiles that may be creating pathways for moisture to get under your shingles.

  • Patch open areas immediately. Consider bringing in a roofing pro to confirm that the area has been properly patched to prevent water damage.

  • Clean your gutters and downspouts at least twice a year.

Many roof cleaning services offer industrial roof cleaning solutions that destroy moss down to the root to remove it for good. 

Here’s a tip: make sure that the pro’s cleaning technique won’t void your roof warranty before you agree to treatment. Pressure washing a roof often voids a warranty because many types of shingles cannot sustain the pressure. However, an option like "soft washing" a roof is often acceptable for roof warranties.

Your Questions Answered By a Pro 

Where does moss usually grow on a roof?

Moss and algae often grow on the north face of a home—talk about a natural compass! The reason for the northern location is that moss thrives in a damp environment that also has lots of shade. And the north side of your roof gets the least amount of sun. But moss can also grow on patches of roof that get shade from overhanging trees that provide shade. 

Does softwashing help remove moss?

Yes. The softwash process uses a cleaning solution containing bleach to kill organic growth like moss. The mixture is generally harmless to your landscaping. Still, you might ask your contractor about that if you have any specific concerns. Pro tip: If your driveway or other concrete has stain on it, the softwashing drip down from the roof eaves and leave a super clean stripe on your driveway. So you might want to consider cleaning driveways and sidewalks at the same time that you softwash your roof. The solution sets for a short time and then is rinsed off gently with a garden hose on low pressure.

Can moss cause roof leaks?

Sometimes, moss can cause leaks in your roof. This happens because moss can create a dam and force water to run uphill, which generally leads to leaks because roofs are not designed to handle uphill water.

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