FHB Logo Facebook LinkedIn Email Pinterest Twitter Instagram Plus Icon Close Icon Navigation Search Icon Navigation Search Icon Arrow Down Icon Video Guide Icon Article Guide Icon Modal Close Icon Guide Search Icon Skip to content
Subscribe
Log In
  • How-To
  • Design
  • Tools & Materials
  • Videos
  • Blogs
  • Forum
  • Magazine
  • Members
  • FHB House
  • Podcast
Log In

Fine Homebuilding Project Guides

Roofing

Guide Home
  • Tools and Materials
  • Roof Replacement and Reroofing
  • Roof Ventilation
  • Waterproofing
  • Installing Asphalt Shingles
  • Installing Other Types of Roofs
  • Roof Maintenance and Repair
Job Site Diaries

How to Remove Lichen and Moss from Your Roof

Choose a safe and effective product to clean asphalt shingles without damaging them.

By Mike Guertin
After just 16 years lichen and moss have taken hold on the surface of the asphalt roof shingles on the north side of the house

The first step in maintaining your roof is to roof it right. If you’re not doing the work yourself, choose a qualified professional roofer to do the job. And choose your roofing material wisely. Some roofing will require less maintenance than others. Choices include metal and slate. Some roofings types last longer than others, as well. That said, data shows that you are probably going to choose asphalt shingles, which can last a lifetime, but likely not without some repairs and maybe replacing a few shingles here and there. And, you may need to clean the roof once in a while.

Twenty years ago I bicycled about 500 miles along the Oregon / Northern California coast and marveled at the number of asphalt shingle roofs carpeted with lichens and moss. The roof growth gave character to many seaside and forest cottages. Though the roofs looked cool, I knew the shingles probably wouldn’t last too much longer.

Lichens and moss loosen the granules on the shingle surface
Lichens and moss loosen the granules on the shingle surface exposing the asphalt and fiberglass base materials. The damage can reduce shingle lifespan.

Lichens and moss accelerate shingle deterioration by loosening shingle granules and exposing the asphalt and fiberglass base materials. The granules aren’t just there to color the shingles; they protect the base materials from sunlight and weathering.

About five years ago, I noticed a few patches of lichens growing on the north side of my roof. Like most lazy homeowners, I ignored the problem. Then about two years ago, when the roof looked like those out in the Pacific Northwest, I knew I couldn’t put off treating the growth any longer.

There are several bad remedies — pressure washing, bleach, ammonia, TSP … that can either damage the roof shingles or damage surrounding landscaping plants. Several name-brand cleaners that aren’t harmful to the roof shingles and less damaging to plants (Jomax, Spray And Forget, Wet and Forget, …) have alkyl dimethyl benzyl ammonium chloride or octyl decyl dimethyl ammonium chloride as the active ingredients.

A heavy spray of solution will kill the lichens and moss but results take time
A heavy spray of solution will kill the lichens and moss but results take time.

I used a pump sprayer and applied a heavy mist to the roof two times about an hour apart. The recommendation for most of the products is to hose down plants that may get dripped on when applying the solution to the roof. I didn’t hose down any plants before spraying the roof and none suffered ill effects from overspray or drips.

According to some manufacturers the spray is ‘reactivated’ each time it rains and will remain effective at preventing new growth for three to five years.

 

Two years later the roof is lichen and moss free
Two years later the roof is lichen and moss free. But the splotches of missing granules where the plants attached themselves is evident.

Nothing happened for a couple of months; then slowly the lichens and moss began to turn brown and gray. It took over a year for all the growth to die, dry up, and fall off the roof. It was only then that damage to the roof granules became obvious.

I installed “35-year” warranty shingles when I built the house 21 years ago. Hopefully the shingles will last another 15 years, but the lichens and moss may have shortened the shingle life by 5 years or more.

 

I’ve used the same products on the roof of my in-laws house in Florida and my mother’s patio pavers (also in Florida) to clean algae stains — and three years later, the roof and pavers are still stain-free.

 

 

(c) Mike Guertin 2017

Sign up for eletters today and get the latest how-to from Fine Homebuilding, plus special offers.

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters
Previous: Plumbing Vent Boot Flashing Repair: Method 2 Next: Refinishing a Rusty Metal Roof

Guide

Roofing

Chapter

Roof Maintenance and Repair

View Comments

  1. pfargis | Sep 08, 2017 08:21pm | #1

    I can't tell you the chemistry of why it works, but using Joy, the dishwashing detergent, full strength or very slightly diluted has killed moss and lichen for me on several roofs. I picked up the tip from a woman who was a chemist. Don't rinse it off. just leave it on and the growth will disappear in about 10 days.

  2. John_van_Tuinen | Sep 16, 2017 11:26am | #2

    Hi, what product did you use in this roof?

    1. User avater
      mike_guertin | Sep 19, 2017 11:27am | #3

      On this roof I used Spray and Forget. Other products have the same active ingredient

  3. tywalker247 | Sep 20, 2017 11:36pm | #4

    Hi Mike, I love in Kodiak, Alaska. We see a lot of moss growth on roofs here. Sometimes even young spruce trees growing. We have used zinc strips, I believe called "moss out" I have also seen copper strips or copper pipe fastened near the ridge. Seems to work better than any chemical spray.

    1. User avater
      mike_guertin | Sep 22, 2017 02:57pm | #5

      You are absolutely right that zinc and copper strips work to prevent and to kill exisiting moss and lichens. Several companies make strips that slip under a shingle course leaving a band exposed. As rainwater runs over the metal strip it washes some of the metal ions over the roof shingles below inhibiting growth. Usually the strips are installed at 5 ft to 8 ft increments up a roof slope depending on how severe the moss/lichen/mold threat is.

  4. InspectorDan | Sep 25, 2017 06:53pm | #6

    I use 20% or 30% strength vinegar (grocery store vinegar is 5% strength) as a less toxic weed killer in my yard. I wonder if the stronger vinegar solution would eradicate moss/lichens as well.

  5. Albany_Chris | Feb 26, 2021 01:41pm | #7

    This is a really valuable article. Although we all have heard that moss can damage a roof I didn't really believe it was a big deal until I saw your pictures. I thought that only scraping it off would cause damage but your pictures prove otherwise. Thanks Mike! (yet again).

Log in or create an account to post a comment.

Sign up Log in

Become a member and get full access to FineHomebuilding.com

Roofing

Roofing

A complete resource that includes the best materials and the right techniques to build a sturdy, leak-free, attractive roof on any house

View Project Guide

View All Project Guides »

Become a member and get unlimited site access, including the Roofing Project Guide.

Start Free Trial

Tools and Materials
  • Roof Coverings
  • Roofing Materials
  • Power Tools
  • Handy Helpers
  • Staging and Ladders
  • Safety Equipment
Roof Replacement and Reroofing
  • Preparing the Old Roof
  • Sheathing
  • Installing the New Roof
Roof Ventilation
  • Venting Basics
  • Installation
Waterproofing
  • Underlayment
  • Drip Edge
  • Flashing Adjoining Walls
  • Dormer and Skylight Flashing
  • Chimney Flashing
  • Vent Flashing
  • Gutters
Installing Asphalt Shingles
  • Calculating Shingles
  • Layout
  • Installation
  • Valleys
Installing Other Types of Roofs
  • Cedar Shingles
  • Metal
  • Low-Slope Roofs
  • Slate and Tile
Roof Maintenance and Repair
  • Assessing the Problem
  • Repairing Asphalt-Shingle Roofs
  • Other Roofing Repairs

Fine Homebuilding

Follow

  • twitter
  • facebook
  • instagram
  • pinterest

Newsletter

Get home building tips, offers, and expert advice in your inbox

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters

Membership & Magazine

  • Online Archive
  • Start Free Trial
  • Magazine Subscription
  • Magazine Renewal
  • Gift a Subscription
  • Customer Support
  • Privacy Preferences

Taunton Network

  • Green Building Advisor
  • Fine Woodworking
  • Fine Gardening
  • Threads
  • About
  • Contact
  • Advertise
  • Careers
  • Copyright
  • Terms of Use
  • Site Map
  • Do not sell or share my information
  • Privacy Policy
  • Accessibility
  • California Privacy Rights

© 2023 The Taunton Press, Inc. All rights reserved.

X
X
This is a dialog window which overlays the main content of the page. The modal window is a 'site map' of the most critical areas of the site. Pressing the Escape (ESC) button will close the modal and bring you back to where you were on the page.

Main Menu

  • How-To
  • Design
  • Tools & Materials
  • Video
  • Blogs
  • Forum
  • Reader Projects
  • Magazine
  • Members
  • FHB House

Podcasts

  • FHB Podcast
  • ProTalk

Webinars

  • Upcoming and On-Demand

Podcasts

  • FHB Podcast
  • ProTalk

Webinars

  • Upcoming and On-Demand

Popular Topics

  • Kitchens
  • Business
  • Bedrooms
  • Roofs
  • Architecture and Design
  • Green Building
  • Decks
  • Framing
  • Safety
  • Remodeling
  • Bathrooms
  • Windows
  • Tilework
  • Ceilings
  • HVAC

Magazine

  • Current Issue
  • Past Issues
  • Magazine Index
  • Subscribe
  • Online Archive
  • Author Guidelines

All Access

  • Member Home
  • Start Free Trial
  • Gift Membership

Shop the Store

  • Books
  • DVDs
  • Taunton Workshops

More

  • FHB Ambassadors
  • Reader Projects
  • Podcast
  • FHB House
  • Customer Support

Account

  • Log In
  • Join

Newsletter

Get home building tips, offers, and expert advice in your inbox

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters

Follow

  • twitter
  • facebook
  • instagram
  • pinterest

Join All Access

Become a member and get instant access to thousands of videos, how-tos, tool reviews, and design features.

Start Your Free Trial

Subscribe

FHB Magazine

Start your subscription today and save up to 70%

Subscribe

We hope you’ve enjoyed your free articles. To keep reading, become a member today.

Get complete site access to expert advice, how-to videos, Code Check, and more, plus the print magazine.

Start your FREE trial

Already a member? Log in