Roof Problems: What Are Moss, Algae and Lichens?

In the world of roof cleaning, moss, algae and lichens are something we encounter every day. The untrained eye may be unable to tell difference, especially when looking at the roof from a distance. You may find any of these plants growing on the roof, but each of them brings a different set of roof problems to contend with.

It may help to know the difference between moss, algae and lichens so that when you are cleaning the roof (or hiring a professional roof cleaner), you know what is required. This article will explain what moss, algae and lichens are, the roof problems these plants can cause, and what you can do about it.

What are moss, algae and lichens?

Moss

Moss is a classified as a ‘bryophyte’, meaning that it reproduces through spores instead of flowers or seeds. Moss is green and has a spongy feel, and it has tendrils that grow in an upward direction. It doesn’t grow when submerged in water, although it does need moisture in order to grow. The wind (and sometimes animals) can carry moss spores to your roof from anywhere nearby.

It tends to like a north-facing roof that doesn’t get too much sun – the more damp the roof, the better for moss. That’s why, with our typical Northwest weather, roof cleaners in Liverpool are never out of work cleaning moss from roofs!

If you have a tree overshadowing your house, this could be another reason why moss grows on the roof. It also consumes water and nutrients from any debris on the roof, like damp leaves, which is another of the many reasons to get the roof cleaned regularly!

What problems does moss cause to the roof? A few, in fact: moss damages the performance of asphalt shingle, and causes the leading edges to curl or lift up. This can result in the wind blowing shingles off the roof. A build up of moss on the roof can also cause moisture damage and leakage, so if you don’t clean the moss from the roof, you may find you also need roof repairs. 

Algae

Algae is classified as a thallophyte, which is a simple plant-like organism that lacks differentiated stems, leaves, and roots. The most common growth on a roof, it grows in water, grows in clusters and prepares its own food.  Like plants, it grows through photosynthesis. When you have black or green streaks on the roof, algae called Gloeocapsa magma is probably the culprit.

Like mold, algae spores are carried to your roof by the wind, from around the local area. Another similarity with roof moss is that that roof algae loves moisture and doesn’t like the sun - so the conditions that suit moss also suit algae. Algae is a tricky substance though; it has a protective sheath that stops the sun’s UV rays from harming it.

What does algae do to the roof? Unfortunately, it damages shingles because it feeds on the asphalt’s limestone, which weakens the structure of your roof over time.

Lichen

Lichen is a little more complex than algae, since it is made up of both algae and fungi. It isn’t actually classified as a plant, but a fungus that coexists with algae and needs it to survive. Lichen has three types: foliose, fruticose, and crustose.

Lichen does look similar to moss in appearance, but it isn’t the same. It can grow in a range of colours, from blue and green to yellow, brown, orange, red, black and grey.

Unlike moss and algae, lichen also needs sunlight to grow. It also requires moisture, oxygen and nutrients.

How does lichen damage the roof? It traps humidity against the roof structures, resulting in gradual erosion to shingles and tiles, which can become distorted or break over time. Lichen can take a long time to grow on a roof, but when it does, it’s the hardest to get rid of. That’s because lichen latches onto the protective layers of the tiles, which can come off when the lichen is removed, leaving holes. For this reason, prevention of lichen on a roof is better than having to call a roof repair professional!

If you are looking for professional roof cleaners or roof repairs in Liverpool, look no further. The friendly team at Saxon Roofing will be happy to help, whatever the problem with the roof.