Photo by Carissa Weiser on Unsplash. A shingle roof covered with shades of green moss.

Even in a dry climate like Arizona, moisture can build up in nooks and crannies over time. And when moisture builds up, moss can sprout. If you’ve noticed a bit of moss growth on your shingle roofing after the damp of monsoon season, here’s a quick guide on how to easily clean up the plants before they grow out of hand.

Why Care About Moss?

Moss develops on shingle roofs when moisture builds up. In a state like Arizona, given the hot climate, many homes are equipped with light-colored or “cool” roofs. These tend to be made out of materials that are porous or more susceptible to erosion, so if you notice splotches of green or even black-brown growths, this means the integrity of your roof has already been affected. 

Even if you don’t have one of these more sensitive heat-reflecting roofs, any kind of plant growth on the roof is an eyesore for a homeowner. So even if function isn’t immediately affected, your curb appeal certainly will be!

Moss can be extremely damaging to shingle roof structures. We’ll discuss how this happens in the next section.

How Does Moss Grow On Roofs?

Sure, you probably understand the idea that moisture breeds both small-celled organisms and bacteria. But what you likely don’t have a significant background in is the behavior and growth patterns of non-vascular plants.

A non-vascular plant, like moss, is one that absorbs water and moisture through its exterior leaf system rather than through its roots. This is why it can develop a glossy, almost “slimy” sheen, whereas a tree, whose water is stored in an underground root system, is covered above ground by a hard and durable trunk. 

If you have a north-facing roof, especially one underneath a tree or shady structure, it’s more likely that moss will grow on it. Additionally, strong winds and natural animal migration patterns can carry moss spores from one roof to the next. 

What Does Moss Do To Shingles?

Moss is extremely damaging to shingle roofs over time. Because of their high moisture content, moss can cause water damage to shingles, causing them to curl and lift off the underlayment. If moisture stays trapped in the shingles long enough, this dampness can creep through the roof structure and cause further damage inside the house. 

Eventually, the integrity of the shingles will be so compromised that you will either have to repair or completely replace the roof. 

How Do You Remove Moss From The Roof?

Removing moss from a roof isn’t necessarily a difficult process, but it does require some professional and industrial equipment that most homeowners don’t have lying around. You’ll first need to get on the roof with an appropriately tall ladder. Then you’ll use a high-powered sprayer, filled with a cleaning solution made of detergent and liquid chlorine bleach, to pressure wash the shingles. However, too much pressure can actually cause the shingles to detach from the roof and fall off, so it can be a delicate process. 

Rather than taking all of this on by yourself, it’s usually recommended to hire a professional to take care of roof moss removal for you.


Contact Express Roofing for more information today.