Is moss bad for your roof?

The big question: Is moss bad for your roof? Do I need to be worried about it? What’s the worst that can happen, anyway?

Here at Northwest Roof Maintenance, the question we hear more than any other, “is moss bad for my roof?” You might be hopeful to hear that moss isn’t that bad but the truth is about what you’d expect.

The answer is simple: Moss is bad for your roof. If your roof has moss on it, roof moss removal is something you need to address sooner rather than later.

In this article

  1. Reasons it’s bad to have moss on your roof
  2. How to prevent moss from growing and remove moss from your roof
  3. How to prevent shingle damage when removing roof moss
  4. Can you pressure wash moss off a roof?
  5. Can I use bleach to kill the moss on my roof?
  6. Roof moss prevention tips
  7. Contact a roof moss removal expert

Why is moss bad for your roof?

Moss thrives in dark, cool, wet climates. Sound familiar?

There’s probably not a single roof in the Pacific Northwest that’s immune from moss growth. And sure, sometimes moss can give a steeply pitched roof a charming fairy tale look like something straight out of the Enchanted Forest.

But there’s a darker side to moss growth. No matter whether you have cedar shakes, tiles, or composite shingles, moss is bad for your roof!

Here’s why:

  • Moisture – By its nature, moss is wet and constant moisture on your roof can cause devastating amounts of rot.
  • Growth – Moss is insidious and grows steadily. As it grows it can push under shingles, tiles, and shakes, pushing them up and creating damage to your roof.
  • Leaks – The damage to your roof caused by moss growth can lead to holes, thin spots, and eventually leaks.
  • Pests – Bugs and rodents may be attracted to moss on your roof. The result is frustrating and hard to eliminate pest infestations.
  • Weight – You’d be surprised at how heavy a big mat of moss can be. Moss is spongy and holds a lot of water. There may be hundreds of pounds of added weight on your roof. That’s weight your roof wasn’t designed to support.
  • Curb Appeal – Are you thinking about selling your home? Moss can be a red flag to picky home buyers and home inspectors, potentially costing you thousands of dollars.
  • HOA Fines – If your HOA is particularly picky, you may face a fine for allowing moss to grow on your roof.
  • Danger – Moss is slick and slippery. You’re much more likely to fall and get seriously hurt if you’re walking on a moss-covered roof!

Moss prevention & removal


An ounce of protection is worth a pound of cure. It’s a cliche for a reason!

Our roof cleaning and maintenance team rely on preventive treatments. These treatments kill moss and stop moss from growing. On composition and tile roofs, we apply a water-based zinc treatment that kills any moss. Once the moss is dead, a liquid spray soaks into your shingles, ensuring that new moss doesn’t take root. If you have a cedar shake roof, we have a specially-formulated copper treatment. Copper prevents moss from growing on your cedar roof.

Copper treatments have extra benefits, including:

  • Repelling insects – Copper doubles as a pesticide, keeping damaging powderpost beetles and termites at bay
  • Protecting roof structure – The copper moss prevention treatments we use also reduce warping, splitting, and other issues caused by moisture

DID YOU KNOW: Zinc-based moss treatments may leave a white residue on your roof. This is natural and completely harmless.


How we remove moss without damaging shingles

Of course, if you already have moss on your roof, the best place to start is with a thorough roof cleaning and moss removal. We’ve developed a 3-step process designed to remove moss without damaging your roof! Here’s how:

  1. We start by gently brushing away moss by hand, freeing it from your shingles.
  2. Using compressed air, we blow the loosened moss and debris off of your roof. We get every nook and cranny, even the hard-to-reach-spaces between shingles.
  3. Finally, we clean up the debris and make sure you’re happy with how your roof looks.

Do you want to maximize the life of your roof? A moss prevention treatment applied to a clean roof is a great way to protect your home!


Can’t I just pressure wash the moss off of my roof?

Pressure washing can remove moss from the surface of your roof but there are drawbacks:

  1. Pressure washing is NOT recommended for roofs with composition shingles. You’ll damage the shingles and reduce the life of your roof.
  2. Pressure washing can drive moisture deeper into your roof. The result is even more rot and long-term damage.
  3. Pressure washing doesn’t always remove the moss that’s between shingles. That’s why we use compressed air to remove moss from most roofs.


What about using bleach on my roof? Won’t that kill the moss?

Bleach and other household cleaners will kill moss. However, many cleaners are corrosive, causing structural damage and unsightly discolorations.

Remember, you don’t want to just kill the moss, it needs to be removed, too.


More moss prevention tips

  1. Have you trees pruned. Branches overhanging the roof can drop moss and encourage additional moss growth.
  2. Keep your gutters clean and unclogged. Moisture leads to moss which leads to more moisture which leads to roof damage!
  3. Get your roof inspected regularly. Stop moss growth before it starts.


Worried about moss on your roof? We can help!

The Crew


Do you see moss on your roof? Or are you noticing bits of moss or lichen on the ground around your home after a big storm? Moss might be damaging your roof!

Contact us online or call (360) 910-8938. Schedule your free no-obligation inspection from our moss removal and prevention team. We’ll answer your questions and help you understand the best way to protect your roof from damage caused by moss.

We’ll never try to sell you a new roof. We’ll only recommend the services you need to keep your roof in great shape for as long as possible. Read reviews from our satisfied customers and see for yourself!

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