Moss Growing on Your Roof Can Create Costly Repairs

Here in the Pacific Northwest, courtesy of the abundant rainfall, we’re fortunate to have some of the world’s most beautiful forests, and tourists from around the world boost our economy as they visit to appreciate these treasures, where huge, moss-covered trees draw millions of eyes and camera lenses. 

As beautiful as that moss is and no matter how many calendars and screens it graces, it is something you absolutely do not want growing on your roof. It reduces a home’s curb appeal, it presents threats to both the home and people, and, when it really builds up, it can be difficult and/or expensive to get rid of.

Moss Growing on Your Roof Can Create Costly Repairs. “


moss on house roof

How Does Moss Get on Roofs? 

Moss grows well in damp, shady conditions, and the wet, humid periods of the year that Bellingham experiences create a perfect setting for moss to grow. The tiny spores moss produces become airborne and wind up on roofs and other surfaces where it can grow, and dampness allows the spores to grow into moss and establish root systems. Once the moss is there, it soaks up water from rainfall, worsening the damp conditions.  

North-facing roofs and roofs that get a lot of shade from trees are especially susceptible to moss growth. In wet environments, moss grows quickly and develops into a mat that can get to be as much as a few inches thick.  

What Are the Dangers of Moss on a Roof? 

Moss can be dangerous because mossy surfaces are slippery, especially when wet. If you have to go on a roof to paint, to clean gutters, to remove debris, or for any other reason, there is a safety risk if moss is present. 

The other danger moss presents is to the roof itself. As the roots establish themselves and grow, they can lift shingles up. The dampness also promotes the growth of bacteria and mold, and wetness penetrates into the roof, eventually causing it to leak. Then the moisture that penetrates the home can lead to mold growth inside as well, causing more damage. In really severe cases, the water damage can cause the roof structure to decay, rendering it unsafe. 

These types of roof and interior damage also tend to be very expensive to repair. Moss on a roof is a big deal and has to be taken seriously.

” The danger of moss lies in its ability to retain moisture. When moisture like rainwater or humidity settles on a roof, it typically air dries before it can linger for too long. When moss covers the roof, however, it can trap the moisture, preventing it from properly evaporating.”


moss on roof bellingham

How Can I Remove Moss from My Roof? 

First, let’s rule out what might seem like the easiest and most obvious solution: high-pressure power washing. Power washers can actually cause more damage to the roof by forcing more water under the shingles and into the roof itself. 

Here are some things that you can do: 

  • Use a garden hose and scrape or brush by hand to remove the moss. This works best when the growth is in its earlier stages and is not thick or widespread. 
  • People also apply bleach, which kills moss and makes it easy to remove. However, using bleach comes with some serious drawbacks. Bleach is highly corrosive, it will also kill other plants it comes into contact with, and it can leave stains on the roof. If you do decide to use bleach, then you should wear personal protective equipment, you should dilute it (which will make it less effective and may translate to more work for you), and you should be careful to avoid spills and runoff into the gutters. 
  • The best DIY way to get rid of moss is the application of moss control powder, which is made from zinc sulfate and kills moss. Unlike bleach, it will not cause stains or damage to the roof, but it is harmful to plants and animals, so it’s important to be cautious when using it, especially if there is a chance it can get into aquatic ecosystems. To treat moss-covered roofs, a lot of professional services use this method. 
  • You can also Call Whatcom Pressure Washers! We have our own very effective system that we’ll talk about at the end, but it’s safe, it’s eco-friendly, and it gets the job done! 

If you notice moss growing on the roof, don’t delay in addressing it. Like many other problems, it’s a lot easier (and less expensive) to deal with earlier rather than later. 

How can I Prevent Moss from Growing on the Roof? 

If you want to prevent moss from growing on the roof, there are a number of options for you:  

  • If you have tree branches over or near the roof, trim them to address the shade issue and also to make it a little harder for moss spores to get from the tree to the roof. 
  • Regularly inspect the roof and your gutters for debris such as leaves and sticks, and remove such debris in short order when you find it. Keeping gutters clear prevents water from backing up and accumulating on the roof. 
  • You can also nail zinc strips to the ridge caps that run along the peak of your roof. After a rain, the strips release zinc onto the roof, and it works as a strong growth inhibitor. This is a safe and very effective way to prevent moss from growing. Zinc strips can also last up to a year, making them a great value for the money.

” It’s not a bad idea to suggest to customers that overhanging tree branches are what’s keeping their roof moist in the first place and allowing the vegetation to grow. Pruning the surrounding trees will let the roof and the rest of the building dry out more quickly. ”


Let Whatcom Pressure Washers Clean Your Roof The Right Way 

At Whatcom Pressure Washers, we use a technique called soft washing. As opposed to high-pressure washing, which we’ve explained can damage the roof, this method applies a softer touch. It removes moss, lichen, and stains without harming plants or the roof itself, and it leaves your roof looking like new. With our soft washing treatment, you get the protection of your investment without any worries about structural or environmental damage. It’s truly the way to go! 

Getting started is easy. All you have to do is reach out to us, and we’ll be glad to send an expert out to inspect your property, make recommendations, and provide a quote. We’re a Bellingham-area leader among companies that clean roofs, gutters, and the exteriors of houses and windows, and we guarantee you’ll be happy with the work we do.  

Contact us today! 

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