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Ask a Pro: Is Moss on My Roof Harmful?

Posted January 16, 2020 by Patrick Morin
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As a Portland homeowner, it’s likely you’ve found yourself wondering, “is moss on my roof harmful?” The short answer is yes. Moss on your roof is harmful. If left untreated, moss can cause decay, shifts in tiles, or disintegrate your roof over the course of time.

Sometimes the sight of moss can be beautiful. On forest floors, growing up tall trees, or even artfully lining walls. However, there are plenty of times when moss can be dangerous and damaging to our properties.

But is this something you can do yourself? Or is it better to leave a job like this to the professionals?

Let’s dive into the topic of moss control and why it may be best to let a professional handle this pesky problem.

Is Moss on Your Roof Harmful?

Moss is a natural element. It grows visibly throughout woods and on trees. And, while not directly harmful to you, it can cause significant roof damage. 

So, is moss bad for your roof?

By nature, moss is a wet plant. This kind of consistent moisture on your roof can cause significant decomposition and rot. On top of that, as it grows, it can steadily push away your tiles and shingles, leaving holes and causing leaks. If that wasn’t enough, moss attracts all manner of bugs and rodents, which can cause major secondary issues.

Because moss is a plant that thrives in the damp, it’s an especially porous plant. So it’s only going to continue to soak up ambient water and dew, which can add hundreds of pounds to the overall weight on your roof. Your roof was carefully designed to hold only what is necessary, so this additional weight could spell disaster.

If you’re considering selling your house, you may find it difficult to move past the expectations of your potential buyers. Mossy roofs don’t add to curb appeal, unfortunately, and it can suggest to these buyers that other elements of your home have not been adequately maintained. 

On top of that, if you’re part of a homeowners association, you could actually incur fines because of the moss on your roof. This is because it is not only unsightly but potentially dangerous because walking on moss is challenging. You’re more likely to slip and fall if you’re doing other kinds of roof maintenance.

What Causes Moss to Grow on Roofs?

Moss thrives in particularly wet, chilly, and shaded environments. This is a notable concern in areas like Portland, but certain species of moss can persist even in warmer climates. 

Moss spreads through spores and they depend on the wind to transport these spores. It should therefore come as no surprise that you will find moss growing in higher spots, like roofs, especially if they’re shaded by larger buildings or trees. Moss is also more likely to grow on roof tiles made of clay or concrete as they have porous surfaces. 

There are four main variables that can contribute to the growth of moss. These are:

  • Dirt on the roof
  • Leaves and other dead plants
  • Excess moisture
  • A lack of sunlight

It’s simple. The growth of moss starts with dirt on your roof. The texture of this dirt makes it easy for moss to build up in small pockets as well as gives it something to grip to. If a layer of dead leaves and other vegetation gathers on your roof over dirt, you’ve created the perfect breeding ground for moss to grow. 

Add moisture and a lack of sun and you have the ideal growing conditions for moss. 

Different Types of Moss

Despite the fact that there are several kinds of moss species all over the world, there are three main varieties that often creep up on our houses. Over time, our experts have been able to differentiate between these three categories. 

Roly-Poly Moss

This is a type of pervasive moss that can actually remove the shingles from their mastic strips. They often sprout at the extremities of your tiles, shake, and shingles. You can spot these ones by their vivid green hue or the fact that they occasionally seem to sparkle.

Spindly Moss

This one is more difficult to see, as it tends to embed itself into a shingle. Once it’s settled, it begins to erode the tile. This kind of moss is a particular nuisance because you often don’t know it’s there until your shingles start to fall apart.

Furry Moss

You’ll find furry moss mostly on wood roofs, but you will sometimes see it on a tile roof. It’s distinctive in that it typically has leaves sprouting alongside it. This moss is also a clear indicator that your roof has wet rot, as it only tends to grow on damp wood.

Why Have a Professional Remove Roof Moss

Moss can be difficult to remove and it spreads quickly. In fact, these layers may thicken during the rainy season. These are all risks to people who do not have the right training and experience in moss removal. You also need to have the right set of chemicals to do the job well. 

Plenty of DIY blogs out there tout solutions that may actually do more harm than good. Certain ingredients, like bleach and vinegar, can corrode and degrease your roof tiles, which means they’ll lose the asphalt coating protecting them. Mixing your own cleaning agents at home can also be dangerous.

Additionally, while a pressure washer can help, most commercial options simply aren’t suitable against stubborn moss. 

A slip or one wrong spray could cause damage to your home. Take into account the danger of being on the roof with a high-pressure machine and it spells out a recipe for disaster.

The professionals have all the right tools and know-how to do the job safely. Professionals can guarantee higher-quality cleaning while ensuring that their cleaning solutions are non-toxic, effective, and ecologically friendly.

On top of that, professional roof cleaners can take more effective, preventative measures like:

  • Applying biocides
  • Applying moss-resistant products and coatings
  • Regular inspections

Preventative Measures You Can Take

Once all that pesky moss is gone, you’re going to want to maintain your roof! Fortunately, there are a few steps you can take to reduce the likelihood of moss growth. Regular cleaning is important and there are a few steps to this. Remember that when you’re working on your roof you want to ensure you’re always wearing the right gear. 

This means having a stable ladder system, shoes with a good grip, a hard hat and if possible, a safety harness. 

Prune Your Trees

Pruning your trees and keeping your roof leaf-free goes a long way toward preventing the fertilization of soil on your roof. Pruning any nearby trees and removing dead branches, twigs, and leaves will prevent the moss from growing in the first place. 

Another advantage of trimming back branches is the fact that they won’t hang over your roof. Remember, moss doesn’t just appear out of nowhere. It grows on branches and twigs and a gusty, rainy day could spread the spores to your roof, where it will nestle into the nooks and crannies and make its home in your tiles.

Clean Your Gutters

It’s easy for your gutters to become clogged over time. This means extra debris and excess overflow. This might facilitate the transport of water and plants that are rich in all the right kinds of nutrients moss thrives on. If you want to stay on top of this problem, you’ll need to regularly clean and maintain your gutters

While you’re cleaning your roof maybe twice a year, consider doing your gutters every two months, or more often in seasons like fall, where drifting leaves are more likely to settle in your gutters. 

Depending on the size of your home and guttering it might come with some difficulty, but it is well worth the effort.

Aim for Safe Inspections

Traversing a roof is a risky business, and potentially very harmful to your physical wellbeing. We advise walking around your home and inspecting your roof for any obvious ground-level damage. If you suspect there’s a problem call in a specialist to do a free roof inspection.

Any roof cleaning company worth their salt will offer consultations for free, as it only serves cements your relationship with them further. Take advantage of this and work with someone you can trust.

Keep Your Roof Clean and Sturdy

You know now that as aesthetic as moss can look, it has no place on your roof. Not only do you have the answer to your question of “is moss on my roof harmful?” but you should now have all the tools you need to get rid of it. 

There’s so much more to moss and roof repairs than you may have originally thought. We’re here to help you eliminate this pesky plant and take the danger and guesswork out of your hands. 

We know a thing or two about roof maintenance and how to keep your roof looking great, no matter the season, no matter the weather. Get in touch with us today to schedule an inspection for your roof.

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