If you have moss on your roof (or another similar problem, like lichens, algae or fungus) it might be tempting to ignore it. Isn’t it just a cosmetic issue, after all? The problem is that roof moss doesn’t just affect the look of your home. Roof moss can cause serious damage, and it should be addressed with the help of an experienced professional.

What Is Roof Moss, and Why Is it so Bad in Portland?

Moss is a type of plant that does not have pronounced roots or flowers. It’s known for growing in poor soil—or even no soil at all—and likes cool, rainy weather. Unlike flowering plants, moss is dependent upon moisture to reproduce. Moss spores, once ripened, can easily blow about. If they land in a location with enough moisture, the spores will start to grow.

At All Surface Cleaning Company, we often comment that “Portland is the roof moss capitol of the world.” It sounds like we’re being cheeky, but we’re serious about the message. There are few other places in the world with weather conditions like Portland’s. We have all the necessary elements for an abundance of roof moss:

• It rains frequently, so our houses and yards almost continually damp.
• The rains are relatively light; they keep things damp without washing organic matter away.
• We have large, established trees that provide shade and act as a source of organic matter.

Types of Roof Moss and Algae

Moss and roof type A

One of many types of roof moss

There isn’t just one type of roof moss, and there isn’t just one way to remove it from your roof. As experienced professionals who deal with Portland roof moss on a regular basis, we can examine the growth patterns of moss and other plants on your roof. Identifying them properly helps us remove them the right way.

Worldwide, scientists recognize more than 22,000 different kinds of moss. That means it’s extremely likely that there is more than one species of moss growing on your roof. Some types of moss form on the ends of roof shingles and tiles and can actually lift them up and away from the roof itself, if allowed to grow under them. Other types of moss are associated with trees, including maples and birch trees that grow over the roof. Still others are associated with specific shingle types, like mosses that are known for growing on decaying wood tile roofs.

Other plants may be involved, too. Roofs can be covered in algae or lichens. Algae is often mistaken for mold or mildew. It can appear in several colors, but black algae is the most notorious. Lichens are actually made up of algae and a fungus living together symbiotically. They can appear in several colors as well.

Why Roof Moss Hurts Your Roof

Moss (as well as lichens) aren’t just a superficial issue. They can hurt roofs of all types by holding excess moisture against the surface of the roof. This extra moisture causes the roof to deteriorate faster than it normally would.

As a mossy roof endures the seasons, extra moisture can cause frost damage. On composition shingles, it causes damage to the mineral granule coating. On cedar shakes, it causes fiber damage. On tile, it causes cracking as the water freezes and expands. All in all, there are numerous ways moss can cause damage to your roof.

How Long Can I Put This Off?


From moss to lichens to algae and fungus, you don’t want to take this problem lightly. With each season, moss on your roof causes accelerated damage and deterioration. While you don’t have to panic, sooner is better than later when it comes to roof moss removal. An appointment with a professional should be given priority in your calendar of household maintenance.

Treatment: Why Eco-Friendly Is Important

There are many options for cleaning roofs. Don’t let anyone tell you that there is only one option. Your options should change based on your roof type, its age and condition, as well as the type of plant and the extent of the damage.

No matter what, one thing is true: The treatments used to address roof moss can affect your roof, yard and family. If used incorrectly or for the wrong roof type or application, they can corrode gutters and downspouts, increase the flammability of the shakes or shingles, or simply be just an ineffective waste of your money. If certain treatments are not properly rinsed from landscaping, they can damage flowers and shrubs. At All Surface, our focus is on removing moss from your roof as safely as possible. For us, that means doing so in an eco-friendly manner whenever feasible.

How to Contact a Roof-Cleaning Professional

Removing moss from your own roof is generally not recommended. You risk damaging your roof. You also risk damaging yourself if you fall.

There are many benefits that come with hiring a professional:

• You’ll know that the problem will be identified correctly and treated appropriately.
• You’ll leave the dangerous work to a professional.
• You’ll get solid advice about how to avoid the same problem in the future.

If you are like most Portland homeowners, you have never hired a roof-cleaning professional before. And we know you may have many questions. Our friendly roof-cleaning professionals welcome your call and questions. For a home visit and free estimate, call (503) 590-9274. Or you may contact us online.