How To Get Rid of Green Gutter Slime on Your Roof

Key Takeaways

• Green slime is a nasty, slimy build-up of moisture, algae, and moss in your gutters that can lead to issues with your roof.
• Causes of green slime include the presence of algae, moisture stuck on the roof, a lack of sunlight, and incorrect gutter installation.
• Gutters are not always as necessary as homeowners think. Often, all you need to direct water is a downspout, and it can make a significant difference in preventing slime buildup.
• To treat green gutter slime on your roof, it’s best to seek an inspection from a professional service that can identify the severity of the issue and the best solution.

Green gutter slime is notorious in the Pacific Northwest. It’s not caused by your roof or anything you’re doing wrong. Unfortunately, it’s often actually created by your gutter system and how your roof was put together.

Although a gutter system is often seen as a necessity for homes in wet areas, a downspout is often all you need. This guide covers the key things you should know about green gutters and downspouts and how to manage them.

What Is Gutter Slime?

Gutter slime is a wet, slimy build-up of algae and moss in your gutters that gets stuck and doesn’t wash away. This build-up can collect dirt and debris and trap water in your gutters, preventing them from draining properly.

Over time, this gutter slime only gets worse and can disrupt your entire gutter system. In severe cases, this gutter slime can trap moisture on your roof and lead to additional issues like leaks and breakdown of your shingles.

Causes of Green Gutter Slime

Green gutter slime is an all-too-common sight on Portland roofs. Between the wet conditions of Portland and the prevalence of different types of moss and algae, green gutter slime is almost expected to grow after enough time. It is a difficult problem to get in front of because of how stubborn it is, but recognizing the following causes can help.

The Presence of Algae, Moss, or Mold

Algae, moss, and mold spread through spores and by reproducing. If these organisms are around already, then they can spread to your gutters or roof. Because your gutters and roof often have moisture on them, they create the perfect environment for the surrounding spores to latch on and start growing a carpet of roof moss.

Moisture Retention on the Roof

Moisture is an essential piece of the formula for algae and moss growth. If your roof retains moisture or has poor drainage in the gutters, green slime may arise. Recognizing areas of moisture retention on your roof is crucial for preventing an environment where these organisms can grow and thrive.

A Lack of Sunlight and Ventilation

A lack of sunlight and ventilation goes hand in hand with moisture retention. If the roof does not have a chance to dry out, it will only encourage the growth of algae or moss. These conditions are common if your roof is shaded by trees or your gutters are blocked by leaves and debris that prevent airflow—in these cases, the growth of gutter slime is very likely.

Incorrect Gutter Installation

Incorrect gutter installation is one of the most common issues leading to green gutter slime—less experienced services will put gutters in places where they aren’t necessary. When it’s time to install gutters on your new home, these gutter guys install them in places where they don’t need to.

It’s not because they are trying to get more money, they just think that everywhere water drips require a gutter—this isn’t the case.

These gutter guys will put gutters on the dormer, and rather than connect it to the lower gutters with a downspout, they’ll cut the backsides and allow the water to run down the roof where it would’ve dripped anyway. The gutters weren’t even necessary to get this same effect, and now you have water constantly running down your roof.