Every homeowner who has dealt with moss and algae on their rooftop has asked this question. The answer to how fast moss grows, unfortunately, isn’t simple. The rate at which moss grows depends upon a number of factors, such as the amount of rainfall your home receives, the number and type of trees nearby, the amount of sunlight and shade your roof gets throughout the day, and how you’ve handled moss on your roof in the past.

How Fast Does Moss Grow on My Roof?

The simplest answer is this: if you’ve had moss professionally removed from your roof in the past, you’re looking on average at about five to six years before you’d normally notice more moss growth and need to have it removed again. At Keeping It Clean, we’ve never seen moss growth return the following year after a professional cleaning.

But five to six years is an average. Some homeowners will see moss return within three years. Others might not see moss growth return for ten.

Why is there such a difference in how fast moss grows on your roof?

What Causes Moss to Grow On Your Roof

Moss and algae growth depends upon the following factors:

Moss and algae depend upon moisture to grow. How fast moss spreads on your roof is directly related to the amount of rainfall your home receives in a given year. Because rainfall is rarely steady year to year, moss growth is also not consistent. Moss may thrive in a wet year, only to slow its growth considerably in a following dry year.

Moss, algae and lichen need organic material to thrive and expand. Homes with nearby trees that shed their leaves in the fall are in greater danger of rapid moss growth. It’s not just leaves that cause moss growth either. Twigs and branches collect on your roof and impede waterflow. This is why it’s so important to remove all debris from your rooftop every year. Leaves, branches and twigs will backup waterflow, create standing pools of water, and lead to the spread of moss and algae.

Like all organic life, moss needs sunlight to survive. But moss prefers shade, which is why homes with nearby trees that provide ample shade are generally at greater risk for continued moss growth.

How to Slow Moss Growth on Your Roof

So what’s a homeowner to do?

At Keeping It Clean, we advise all of our clients to perform annual maintenance and cleanup on their roof. Removing debris each year is essential to the proper upkeep of your roof, and it will ensure that moss and algae have little organic material to feed upon.

How often should you clean debris from your roof? In the Pacific Northwest, we recommend that you remove debris at least twice a year: once in the fall after the trees have shed their leaves, and again in the spring before heavy rains begin. Removing debris should include thoroughly cleaning all rain gutters and downspouts.

Annual Roof Maintenance:

Proper roof maintenance and cleaning will prevent the growth of moss and algae and ensure the long life of your roof. At Keeping It Clean, we offer affordable professional services not only for moss removal and roof cleaning, but for cleaning your gutters and downspouts as well. Call us anytime or fill out the form below to schedule an inspection and cleaning.