Identifying What’s Growing on Your Roof?

When you have streaks on your roof, there are some different possibilities of what could be causing it. Here are the four types of growth which could be causing the streaks and how to determine which one is on your roof.

There are four types of growth to watch for:

1. Algae

2. Lichen

3. Fungus

4. Moss

Algae Growth

• Extensive Algae growth – in both green and black.

• Different colors are evident.

• Dark appearance is a protective layer the algae have developed to protect itself from damaging UV rays.

Algae, Lichen, Fungus

• Evident in this image are Lichen, Fungus & algae.

• Notice the vent metal has inhibited growth. This observation is what initially prompted researchers to finding metals which prevent algae growth.

• Note the algae-free surface on dormer roof. This is due to exposure to the sun, allowing that portion of the roof to dry faster.

Algae Growth

• Extensive algae growth.

• The area below the window is free of algae due metal flashing… run-off of the metal inhibits growth and algae.

• Algae predominantly grow from the bottom up, due in part to the amount of time water is on the roof.

Lichen & Fungus Growth

• Fungus is predominantly at the shingle edges and keyways.

• Left to grow may eventually damage the shingles by lifting them and further inhibiting water run-off.

Moss

• Moss due partly to low slope, shady location, organic material & exposure.

• Water is retained on the roof; thus essentially aiding the growth.

• Organic material needs to be present for growth or moss cannot take root.

• White: Very Low Algae, Moss, Lichen and Fungus Growth

• Yellow: Low Alga, Moss, Lichen and Fungus Growth

• Red: Severe Algae, Moss, Lichen and Fungus Growth