How Moss and Lichen Are Slowly Destroying Your Cedar Shake Roof

By Dwayne | Forza Roof Cleaning | August 2020

The Unseen Threat to Your Home's Crown Jewel

A cedar shake roof is more than just a covering; it’s a statement of natural beauty and timeless elegance. Its rich, warm tones and rustic texture lend a distinguished character to any home, from a cozy countryside cottage to a sprawling mansion. But lurking on this beautiful surface is a silent destroyer, a living organism that is slowly compromising the integrity of your investment. We’re talking about moss and lichen, the seemingly harmless green and gray patches that are, in reality, a destructive force against your cedar roof.

Many homeowners in Central Ohio and beyond might dismiss these growths as a mere cosmetic issue, a bit of "character" that comes with a natural roofing material. The truth, however, is far more alarming. Moss and lichen are not just sitting on your roof; they are actively consuming it. Understanding the biology of these organisms and the damage they inflict is the first step toward protecting your home’s most prominent feature. At Forza Roof Cleaning, we’ve seen the devastating effects on over 1,500 roofs, and we believe in empowering homeowners with the knowledge to combat this threat effectively.

The Biology of a Cedar Roof Infestation

To understand the danger, you first need to understand the enemy. Moss and lichen are not simply dirt or stains; they are complex living organisms with a tenacious grip on your roof. Lichen, a composite organism arising from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship, is particularly insidious. It attaches to the cedar shakes with a root-like structure called a rhizine. These rhizines are not just surface-level anchors; they penetrate deep into the wood fibers of your cedar shakes, creating microscopic fissures and pathways for water to enter.

Moss, a non-vascular plant, behaves similarly. It establishes a shallow root system that, while not as deeply penetrating as lichen rhizines, creates a dense, absorbent mat across the roof surface. This mat acts like a sponge, trapping and holding moisture long after a rainstorm has passed. A perpetually damp environment is the mortal enemy of a cedar roof, which is designed to shed water and dry out quickly. When moisture is constantly held against the wood, the natural decay process accelerates exponentially.

The Vicious Cycle of Moisture and Decay

The primary problem with moss and lichen on a cedar roof is their incredible capacity for moisture retention. A healthy cedar roof is designed to breathe. The individual shakes expand and contract with changing humidity levels, a process that helps the roof shed water and resist the elements. When a thick blanket of moss covers the surface, this natural process is suffocated. The trapped moisture prevents the cedar from drying out, creating a permanently damp, humid microenvironment right on your roof. It would be like a human wearing wet socks all the time. It doesn't take long to get foot-rot and irreparable damage to the skin on your feet.

This constant dampness is a breeding ground for wood-destroying fungi and bacteria. The very organisms that break down fallen trees on the forest floor are now being cultivated on your roof. The cedar shakes, which should be hard and resilient, become soft, spongy, and weak. They begin to rot from the inside out, losing their structural integrity and their ability to protect your home from the elements. This is not a slow, gentle process; it is an aggressive assault that can significantly shorten the lifespan of your expensive cedar roof, turning a 30-year roof into a 15-year problem.

Furthermore, the physical presence of moss can cause significant structural damage. As the moss thickens, it can lift the edges of the cedar shakes. This lifting action breaks the seamless, overlapping seal of your roof, creating channels for water to run underneath the shakes and directly onto the roof deck. This can lead to devastating leaks, attic mold, and costly structural repairs that go far beyond the roof itself. What started as a small green patch has now become a direct threat to the structural integrity of your entire home.

Why Standard Cleaning Methods Fail—And Cause More Harm

Faced with a moss-covered roof, many homeowners are tempted to reach for a pressure washer or call a company that offers a generic "soft washing" service. This is, without a doubt, the worst thing you can do to a cedar shake roof. High-pressure water will not only fail to remove the deeply embedded rhizines of the lichen, but it will also strip away the top layers of the cedar wood itself, causing irreparable damage and accelerating its decay. It’s a brutal, ineffective approach that trades a temporary cosmetic fix for long-term destruction.

Similarly, many so-called "soft wash" treatments rely on a high-concentration bleach and water solution. While bleach can kill surface-level growth, it does not penetrate deep enough to eradicate the root structures. More importantly, bleach is a harsh, corrosive chemical that is incredibly damaging to cedar. It breaks down the natural lignins and oils in the wood that give it strength and durability, leaving the shakes brittle, discolored, and vulnerable. It’s a scorched-earth tactic that damages the roof as much as the growth it’s meant to remove. For a material as delicate and specialized as cedar, these one-size-fits-all solutions are a recipe for disaster. You can learn more about our approach to different roof types at our shingle roof cleaning and cedar roof cleaning service pages.

The Forza Solution: A Professional Roof Treatment

A cedar shake roof requires a specialized approach, one that respects the nature of the material while effectively neutralizing the biological threat. At Forza Roof Cleaning, we have spent over a decade perfecting our professional roof treatment process. We are not a pressure washing company; we are roof treatment experts who understand the unique challenges of materials like cedar. Our process is designed to be both gentle and profoundly effective, ensuring the long-term health and beauty of your roof.

It begins with a non-invasive drone assessment to fully understand the extent of the infestation. Our crew then utilizes professional-grade ladder standoffs to ensure we never have to walk on your roof, protecting the delicate shakes from physical damage. From a secure anchor point, we use an industrial-grade pumping system to gently apply our proprietary blend of roof-safe algaecides, fungicides and oils. This biodegradable solution is the key to our success. It penetrates deep into the wood fibers to kill moss and lichen at the root, neutralizing the threat without harming the cedar itself. It leaves behind necessary oils for the shake to absorb. Restoring the natural oil content to about 3%. This gets your shakes bio-free and oiled properly, leaving your roof ready to fight nature's daily attack of this beautiful organic roofing material.

Our highly trained technicians work systematically to ensure every inch of your roof receives the treatment. The solution is left on the roof to do its work, and over the following weeks and months, the dead organic matter is gently washed away by natural rainfall, revealing the clean, healthy cedar underneath. We verify the results with a post-treatment drone flight, and we stand behind our work with a quality guarantee. It’s a process trusted by over 1,500 homeowners and even prestigious clients like the Wedgewood Country Club in Powell.

The Bottom Line

Moss and lichen are more than just a cosmetic nuisance on your cedar shake roof; they are a biological infestation that is actively shortening its lifespan and compromising its ability to protect your home. Their root systems penetrate and destroy wood fibers, while their moisture-retaining properties create a permanent state of dampness that fosters rot and decay. Attempting to remove them with harsh methods like pressure washing or bleach will only cause more damage. A cedar roof is a significant investment that requires a specialized, professional roof treatment to preserve its integrity and beauty. Don’t let your home’s crown jewel be slowly destroyed by a preventable threat.

Serving Columbus and Central Ohio: Forza Roof Cleaning provides professional roof cleaning in Columbus, Ohio and all surrounding communities. Call (888) 516-0008 for a free drone assessment.