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Removing Moss on Roofs

How to remove moss from the roof?

Removing Moss on RoofsWondering how to remove moss from your roof? This page has been created to share the various ways to remove moss on shingle roofs. Not only does this page share the methods to remove moss but it also helps you understand the problems that arise from a mossy roof, how to prevent a mossy roof, and overall gives you a better understanding in order to properly deal with moss on rooftops.

*Please refer to the table of contents to skip to any section of this page you are most interested in.

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What is Moss?

How to remove moss on roofsMoss is a plant species that grows really well in moist cool areas. There are many different species of moss. Some common characteristics among these species are that moss does not have flowers or seeds, they must have a damp environment to grow in because they do not have any root system to secure water, and they are usually extremely green with tiny leafs.


What Promotes Moss Growth?

  1. A shady climate. The climate doesn’t need to be too shady but shade is optimal.
  2. Acidic environments. More specifically moss grows optimally at a pH level of 5.0 to 5.5.
  3. Moss grows well on hard surfaces.
  4. Moss needs a moist/humid environment to grow.

How to Kill Moss?

Roof Cleaner Spray

  1. Take away the shade that the moss is growing in.
  2. Turn its environment extremely acidic or turn it into a base environment (above 7 pH levels).
  3. Take away the moisture or water from the moss.

Remove The Shade

Because moss grows well in shaded areas one way to control moss/remove it from roofs or other areas is to remove its shade. This can be done by removing trees, trimming tree branches to allow more sun to penetrate, or remove bushes and other type of plant life that may be blocking the sun.

This method of moss prevention and removal is highly effective but remember that it may be ineffective if the weather is often overcast and cloudy.

Make its Environment Acidic (below pH 4)

There are many common household items that have a pH level at or below 4. These products are highly effective at killing moss. Using these products with a mixture of water or directly to the moss can kill the plant. Be aware that acid products erode certain types of surfaces. By diluting the mixture you can prevent unwanted corrosion.

  1. White Distilled Vinegar (Apple Cider Vinegar As Well)
  2. Orange Juice
  3. Lemon Juice
  4. Tomato Juice

Make its Environment a Base (Above pH 7)

Since moss grows in a pH environment of 5.0 – 5.5 or 6.0, by changing the environment to a base level it will effectively kill the moss. Below is a list of some common household items that are bases. By mixing these products with water or by applying them directly they can kill moss in yards, off of roofs, siding, decks, or other unwanted areas.

  1. Baking Soda
  2. Baking Powder
  3. Salt
  4. Ammonia
  5. Soap
  6. Bleach (Do not mix bleach and ammonia)

Warning: How Not To Kill Moss on Roofs

damage-to-roofs-casued-by-roof-cleaningRoofs are an investment that must be safe guarded. That being said, we want to give you some “what not to do” tips when trying to remove moss off of your roof.

  1. Do not pressure wash the moss off
  2. By using a pressure washer to remove the moss you are going to dramatically reduce the life of your roof. How? The high powered water will remove the asphalt shingle granules which help protect the shingles and ensure a longer life span.

  3. Be careful with using acids to remove moss. If your acidic mixture is too strong or stays on the roof too long, it can eat away at the shingles. If your roof cleaning solution has not been tested previously, make sure you test it on some spare shingles before applying it to your roof.
  4. Do not scrape the moss off of the roof. This can rip, crack, and break the asphalt shingles themselves.
  5. If any water is used to remove the moss, do not spray the water at an upward angle. If you do, this can cause water to go under the shingles and leak into the house or rot the wood decking of the roof.

Roof Cleaner Poll

What roof cleaning application do you most often use?

A poll was taken on by professional roof cleaners back in 2004. The poll gave them three options to rate as to their most preferred roof cleaning solution. We have posted the results of the poll below.

Total Number of Voters: 300

Chlorine/bleach with rinse: 175 Votes at 58.33%
Chlorine/bleach no rinse: 77 Votes at 25.67%
Sodium Hydroxide based roof cleaner: 48 Votes at 16.00%


Why is Moss on The Roof Bad?

Although the reasons are some what debated in the roof cleaning industry there is definitely one common conclusion and it is that moss is not good for roofs. We have posted a few of the reasons commonly accepted within the industry for why moss is bad for shingle asphalt roofs.

  1. As the moss thickens and grows on an asphalt shingle roof it can raise the shingles up (much like a jack under a car). When the shingles get risen it allows water to go under the shingles causing the decking to rot and causing the roof to leak. The raised shingles also pose problems when heavy winds are present because they will catch the wind like a sail and this can cause shingles to be torn/blown off the roof.
  2. A moss buildup on the roof causes more debris to get trapped on the roof. This debris promotes water buildup which makes the roof at risk of much more rotting and leaking.
  3. Moss can actually damage the asphalt shingle components leaving it to break down faster.

Words From The Professionals

Below are some words taken from professional roof cleaners. These quotes are paraphrased from forums and discussions located on various websites on the www. We hope that these words help you understand the process of cleaning roofs from moss, mildew and mold a little better.

“When I first started cleaning roofs from moss I used a mixture with sodium hydroxide and water. Pretty soon after I started using such a compound I began to see a change of color when I rinsed the roof. The water that would come off was a dark brown color. At first this to me seemed like amazing results because I wasn’t just removing moss but I was cleaning the roof to make it look new again. Now after having more experience in cleaning roofs I realize that this brown color was from the chemicals eating away at the asphalt shingles. I no longer use a sodium hydroxide chemical solution.

Because of this experience I use Chlorine to clean roofs from mold, moss, and mildew. My roof cleaning business is located in Florida and I see a lot of roofs. When I clean the roofs with chlorine I don’t bother to rinse the roof after application due to an effort to preserve the green plant life that is part of the clients landscaping. Killing moss with chlorine and non rinsing has worked for me well and my clients are always satisfied.”

“My experiences vary in depth and scope. Some of my experiences with moss on roofs come from servicing clients that have had a previous company attempt to clean their roof. Many of these types of clients experience the moss returning too quickly. In fact, some of these clients have moss return even after having the service performed and zinc strips installed. I have found that both a bleach solution and a sodium hydroxide solution cleans roofs just fine!”

“I have cleaned many roofs and each one of them still looks fabulous a year later. I use a bleach solution on the roofs I clean. Although my services focus on the removal of the mold, moss, or mildew I make sure that my clients understand that it isn’t all about the removal of the moss but also the prevention of it. Some good methods of preventing moss growth is by using zinc or copper strips.

“I always rinse the roof after applying a bleach solutions. If it gets on the plants make sure you have a guy rinsing the plants with 100% water while a guy is rinsing the roof.”


Roof Cleaning Recipe Solutions

We make no claims or promises regarding these homemade cleaning solutions. Please be sure to test the solutions on a shingle that is not located on your roof before applying the moss killer soltution to your entire roof.

Dish Soap Recipe

4 ounces of Ultra Dawn Dish Soap
1 Gallon off Water

Chlorine Bleach Moss Killer Recipe

5% – 10% Chlorine Bleach
90% – 95% Water

Vinegar Moss Killer Recipe

5% – 10% White Distilled Vinegar or Apple Sider Vinegar (100% Vinegar Solution)
90% – 95% Water

Other ingredients that you can experiment with are:

  1. Salt
  2. Baking Soda
  3. Baking Powder
  4. Ammonia
  5. Lemon Juice
  6. Sodium Hydroxide

How To Prevent Moss Growth on Roofs?

There are various things you can do to prevent moss from growing on top of the roof. Below is a list of some of the most basic and some you may never have heard of before but work well.

  1. Keep the roof out of the shade by trimming up trees, shrubs, plant life, or even removing trees completely.
  2. Install zinc or copper strips at the top of the roof ridges.
  3. String copper wire across the roof in intervals using nails or screws on the side of the roof (Do not hammer the nails or place the screws through the asphalt shingles. Place them on the side of the roof, possibly in the faucet.
  4. Keep the roof clean of debris on a regular basis.