You expect to see moss when you're walking in the woods or staring at the north side of a tree. But if you look up at your roof and see moss, that's another matter. Should you do anything about it? What does this suggest about your roof's condition? Keep reading to discover the answers to these and other questions about moss growth on roofs.

Why does moss grow on roofs?

Moss doesn't have true roots — just nubby little root structures. As such, it can grow anywhere that it can "root" itself into a tiny amount of porous substrate. Shingle and shake roofs fit the bill. However, moss will typically only grow on a roof if that roof is moist and shaded. So, you tend to see moss on parts of roofs that are under big tree branches.

Do you need to remove the moss?

It is not a good idea for you to remove the moss yourself. However, you should have the moss removed. Even though moss roots are tiny, they do cause the shingles or other roof material to break down further. If you leave the moss to grow unchecked, you may need a new roof much sooner than you otherwise would.

How do roofers remove the moss?

Roofing contractors usually spray the roof with specialized herbicides to remove moss. These herbicides will kill the moss and cause it to dry out. This happens within a few days of application. The roofers can then return and gently remove the dead moss from your roof. They have tools to do this without damaging the shingles — like you might if you were to power wash your roof. (That's a common move but a bad choice because it damages the roof.)

Can you keep the moss from returning?

Yes, if you are able to keep your roof dryer and less shaded, you can keep the moss from growing back. This usually means having any trees near your roof trimmed way back. If this is not possible, talk to your roofer about periodic herbicide applications. Often if you have the roof sprayed with herbicides every few months, the moss won't grow back.

Moss belongs in forests and on the north side of trees. It's not something you want to see on your roof. Make sure you keep the advice above in mind so you can solve this issue quickly and safely if you encounter it.

Contact a roofer for more information about shingle roofs.