14 July, 2020

What You Need to Know About Roof Moss Removal

If you live in the Pacific Northwest – or any other wet sun-starved climate – you’re familiar with the sight of moss. And while moss can be quite beautiful in the forest, it doesn’t look very nice on your asphalt comp roof. It’s also doing damage. Moss puts down roots, collects and traps moisture, and over time eats away at your roof shingles. I have advised my customers for years that far away the best policy when it comes to your roof is to keep it clean and never allow the moss to grow on it.


Roof moss removal
Roof Moss Removal


But what do you do if you already have moss on your roof shingles? Because every roof is different and not all homeowners have the same needs or budget, there is no one-size-fits-all solution when it comes to moss removal and exterior cleaning and maintenance.


Best Options for Roof Moss Removal

Here are a few of the best roof moss removal options:

Option A: Routine Care

This is what most Puget Sound homeowners should do routinely to prevent moss from growing on the roof in the first place. And it’s also a great way to take care of very light current moss growth on the roof–I’m talking about moss growth that is no higher than the thickness of your asphalt comp roof shingles. It might also be a good option for even thicker moss, but keep in mind 1) you will be looking at dead moss for a long time, and 2) if you aren’t vigilant with treatments, the dead moss becomes the perfect garden for new moss growth and you’ll be right back where you started. If you have anything more than very thin moss or if you need the roof looking great for a sale, don’t use this method. Zinc sulfate powder and chlorine bleach is the most common moss treatment, but there are other options where the environmental concern is high. Here are the steps:

  • Air-blow the loose debris from roof
  • Line roof with moss treatment powder (or spray on liquid form)
  • Clean out gutters and downspouts
  • Clean up debris from ground


Option B: Roof Brush

Roof cleaning by brush can be a good way to go in certain circumstances when moss needs to be removed and water is not an option. It also works well on tougher roof types. Still, it is the least gentle of all the methods we offer and a poor option for many roof types and conditions. It also doesn’t clean as well as the Roof Wash. On the upside, it requires no water or chlorine bleach and it can be less expensive (though that is not always the case).

  • Brush remove moss from the roof
  • Air-blow loose debris
  • Apply moss treatment
  • Clean out gutters and downspouts
  • Clean up debris from the ground


roof moss removal near me

Option C: Roof Wash

For those putting their homes on the market or just need their roof looking as new as possible, a roof wash may be the best approach to moss removal. Please note carefully that this method is neither a soft wash nor a pressure wash. A high-volume pressure washer is used (8 or 10 gallons per minute), but wide-bored specialty nozzles (not available in hardware stores) are required to significantly lower the pressure. It is more abrasive than the Soft Wash, but it uses a lot less bleach and the visual end result is almost always superior since the moss is actually removed. While the roof savvy homeowner can DIY Options A or B, that is not the case with the Roof Wash.

  • Air-blow loose debris
  • Clean out gutters and downspouts
  • Apply cleaning agent
  • Wash all moss from roof using a high volume and low pressure
  • Re-clean gutters and downspouts
  • Pick up debris from ground


Option D: Soft Wash

Soft washing is another method of routine care preferred by many roofing manufacturers. It’s quite effective in killing moss, lichen, and algae and so long as there is very little moss on the roof to begin with the results will be beautiful. It’s also very gentle on your roof. But here are a few possible drawbacks. It is less gentle on your wallet than zinc powder. It also takes a lot of bleach to do the job properly (sometimes 40-50 gallons). Another potential issue is that if you have more than a modicum of moss on your roof to begin with, there will likely be lines of dead white moss fluff all over your roof at the end of the job. Still, it’s a great way to go in certain situations. As with the Roof Wash, the Soft Wash is not for DIY. Here’s the process:

  • Air-blow loose debris
  • Clean out gutters and downspouts
  • Clean up debris from ground
  • Rinse down all plant-life and property that might be damaged
  • Apply cleaning agent (a water + chlorine or oxygen bleach + a surfactant)
  • Rinse everything down again thoroughly

What about Air-Compression Roof Moss Removal?

I have not been thrilled by the results of this method. While it is better for the roof than the brush method, it is labor-intensive, expensive to the homeowner, and the end results are unsatisfactory. It removes the moss but all the dirt and grime remains. (Just imagine taking a shower at the end of a long day working in the garden with compressed air instead of water. It’s kind of like that.)


Best Way to Remove Moss From My Roof

So, what’s best for you and your roof? The goal in every roof moss removal decision is not simply to go with the gentlest approach possible, it’s to go with the gentlest approach possible given your situation. (Also, bearing in mind that “gentlest” on your roof isn’t always the gentlest on your wallet, the environment, or a favorable home sale.) Situational variables are important to think about when deciding which option to go with. Here are a few to think about:

  • Moss – How bad is it?
  • Type – Is your roof asphalt comp, cedar shake, concrete tile, rubber tile, true Spanish tile, aluminum, PVC membrane, torchdown, etc?
  • Condition – Is the roof too old, brittle, or soft, to withstand any type of cleaning? Is it walkable?
  • Outcome Needs – Is your insurance company requiring moss removal? Are you putting the house on the market?
  • Aesthetic Taste – Is the sight of moss on your roof more abrasive on your eyes and mind than any abrasion caused to the roof by moss removal?
  • Budget – Do you have the money to pay for the option you want? Or do you need to get creative and find a cheaper solution? And if you go cheaper now, will it cost you more in the future?


Need Local Roof Moss Removal Near You

Of course, if you live in Seattle, Bellevue, Shoreline, Issaquah, or the surrounding areas, feel free to call us at 206-232-1266 or contact us with any questions. We’re happy to help you find the best option for you and your roof. You can also check out our Evergreen Roof Care page for more information. Evergreen Window Cleaning & Home Maintenance is happy to serve however we can.

We Are Local (WA)

Roof Moss Removal Bellevue | Roof Moss Removal Shoreline | Roof Moss Removal Seattle


We have a general contractor’s license (#EVERGWC908JB) as required by the State of Washington for any kind of pressure washing. We also have our regular business license (UBI#603-000-297), bond, and insurance.