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How to Kill Moss on a Roof

By April 20, 2021Roof
How to kill moss on a roof

Fairytales often will show moss on the roofs to add to the scenery in the movie. We always think it looks nice in the movies and adds to the story, however, in real life, it is not a good thing. Unfortunately, it can cause a roof to degrade. Are you looking at your house and wondering how to kill moss on the roof? Well, hose off the roof, use a cleaning solution, and add zinc strips to keep it from coming back.

Let’s take a look at why you need to know how to kill moss on a it starts and what it does, how to remove it, why you can’t cover it with a new roof, how to prevent future growth, other areas to check, and when to call a professional.

Why You Need to Know How to Kill Moss On a Roof

Even though the green color of moss can add some color to the house, it is not a good thing to have on the roof. Unfortunately, it does shorten the life span of the roof. The quicker you can get it off the roof the better. There is also maintenance you can do to keep it away.

How Moss Starts and What It Does

Moss likes the water from the rain and soaks it up on the shingles and retains it. Then, it grows its roots through the shingles, often lifting them up and causing leaks. It also ruins the roof sheathing and causes it to rot. 

Additionally, after moss starts to grow, it causes the water to often miss the eaves as it tries to drain. Then, it misses the gutters and downspouts and ends up in the yard making puddles and possibly flooding.  You don’t want the standing water as it can seep into the basement and cause mold growth.

Some wet climates will see more moss on roofs than other climates because of the amount of rain that falls. It is important to clean it as soon as you notice it growing.

How to remove moss from the roof

How to Remove Moss From the Roof

The moss might appear dead if it has been really dry, but you still need to remove it. It can’t be done by hand but can be done by using a hose and a cleaner. Here are the materials you will need: garbage bag, garden hose, ladder, and a mix of mild detergent with water. Use 8 ounces of dish soap with two gallons of water.

Step 1: Hold on to your spray bottle and put the ladder against the house near where the moss is. Next, spray the area.

Step 2: Leave the concoction on the moss for 15-20 minutes.

Step 3: After 15-20 minutes, put the hose on low pressure and spray the moss. It should come off the roof. Be careful not to spray under the shingles as they can lift up and cause a leak in the roof and a shingle repair. You do not want this to happen.

Step 4: Any moss that is left on the roof should be able to be picked up and put in your garbage bag. If there is moss that won’t come off, you will need to contact a professional roof inspector for help.

3 Don'ts to kill moss on the roof
Pressure washing to get moss off the roof is not a good idea as it can knock the shingles loose and water can find its way under the shingles

3 Don’ts to Kill Moss on Roof

  1. Scrub the shingles – scrubbing the moss off the asphalt shingles can cause them to become loose and damaged.
  2. Pressure wash the roof– the force of the pressure washing can knock shingles loose and can also cause water to find its way under the roof.
  3. Use harsh chemicals to clean the moss– this can cause deterioration of the shingles on the roof, it is harmful to breathe in, and also cause leaks.

Any of these things above could cause the roof warranty to expire so you want to be careful.

If you find that there are shingles that have lifted, check inside the attic and home for mold growth. If you find it, contact a professional for a plan to get rid of it and to fix the leak and shingles.

Why You Can’t Cover Up the Moss With a New Roof

If you are thinking you can, the answer is don’t! That is like painting over mold in a house. It doesn’t fix the problem and the problem is still alive. You may have a roof that has damaged underlayment and decking and now is a hazard as the roof can collapse. Have a professional check out the roof to see if he/she can remove the leftover moss. He/she can then advise you on the next step.

Adding a new roof over moss can also cause bumps in the roof and the shingles won’t adhere well. Also, if your home is up for inspection, it could get canceled if the insurance inspector notices the moss and sees that the roof is decaying. It will be dangerous for a roofer to go on a roof that has moss, as well as rot and mold that can be going on underneath.

How to Prevent Future Moss Growth

Fix Shade Issues

If you have shade on the home from trees, consider cutting those back. Moss likes the shade and this can help keep it from growing. Also, if you have a trellis or pergola that casts shade on the home, consider moving it.

Add a Metal Strip of Zinc to Kill Moss on Roof

Adding a metal strip of zinc on the roof where the ridge is located will ensure the rainwater flows down the roof. Over time, the strip becomes oxidized and makes it less habitable for the growth of moss or lichen. Just like counter flashing next to the chimney works to keep the water out and flowing down the roof.

Regularly inspect the roof

Regularly Inspect the Roof

Whether you do a roof inspection with a checklist or hire a professional, make sure you take a look around the roof at least once a year or after bad storms. In case it is a snowy winter, make sure you read up about cleaning snow off the roof so you don’t do any damage. Spring might be a good time to do the inspection, especially here in New Hampshire and Southern Maine.

Other Areas to Check on the Roof

As mentioned earlier, a roof inspection checklist is a great way to keep up on maintenance and to find issues before they become problems. If you go in the attic and see there is mold on the trusses, you know there is possibly a leak on the roof. You will need to check the roof or hire a professional.

When to Call a Professional

Call a professional if you need help getting the moss off the roof of the house. Additionally, if you need someone to inspect the roof, or if you have other questions as they are trained to help.


Moss on the roof may look pretty and like a cottage, but it is damaging to the home. Take care to get it off the roof safely and keep it from returning. We can look at your roof when inspecting homes in New Hampshire. Think you may need our services? Leave us a comment below!