Algae, mould and lichen are common and unwanted features on many roofs particular throughout Queensland due to the large amounts of humidity. It can often be hard to distinguish between these three and what you need to do in order to remove it from your roof. In this article James Kelly, owner of Brisbane Roofing Solutions, provides further information on algae, mould and lichen and what it means for your home.


Algae is typically green/brown in colour and creates a thin slimy layer on surfaces. Algae thrive in aquatic atmospheres, however, the algae that grows on your roof grows in a colony which means it doesn’t need to be submerged in water to survive, and once it settles, it grows quickly and spreads spores through the air.


Mould is typically a coating or discolouration caused by various fungi that develop in a damp atmosphere. Mould is not always easy to recognise. It often looks like ‘fuzz’ or appears to be a stain, smudge or discolouration. The most common moulds are black, green or white.


Lichens are a complex life form that is a symbiotic partnership of two separate organisms, a fungus and an alga. It is a slow-growing plant that typically forms a low crusty, leaflike, or branching growth

How to tell if your roof is at risk of attracting algae/mould/lichen?

All roofs are at risk of attracting algae, mould and lichen however, there are certain factors which can increase your risk. These include;

  • Surrounding trees or dense bush, particularly if these overhang your roof.
  • You live in a tropical climate. Algae, mould and lichen spawn in humid and damp conditions.
  • There are local sources of dust, windblown dirt or pollution
  • Lichen in particular is attracted to dark roofs with harder surfaces such as terracotta tiles
  • If your roof is predominately shaded throughout the day this means dew condensation builds up and is not dried up by the sun

What can you do to prevent the growth of algae/mould/lichen?

The best method of prevention is regular maintenance. Cleaning the roof every 2-4 years is an effective way to ensure algae/mould/lichen are not able to build up and spread. A fungicidal wash can also be applied to help remove any existing growths as well as slow future growths that may occur.

Cutting back overhanging trees to ensure maximum sunlight is able to reach the roof and try up any excess moisture build up. In addition to this be sure to clear the roof and gutters of any leaf/debris build up as these also foster growth or algae, mould and lichen.

Additionally, choosing darker colours may raise the exterior roof temperature which promotes faster drying as well as slightly masking some of the aesthetic impacts of spores growing on your roof.

Why should you care about growths on your roof?

While people like to say that dirty roofs lower a property’s value and may make it hard to sell, the “dirt” on a roof actually shortens its life span and can even present a health hazard.

While not all mould (fungi) and algae pose a health danger, some are harmful, especially for older people, younger children and people who suffer from asthma and respiratory problems. The spores on your roof can get inside your home because they end up on the driveway and paths and are easily tracked inside.

If you have a heat reflective coating on your roof algae will also hinder its ability to cool the roof.

Finally, for an aesthetic stand-point, algae/mould/lichen are just not nice to look at! In particular if you are selling your property it may stand to significantly lower the selling price of your home!

If your home is suffering from a roof covered in algae, lichen or moss be sure to contact the experts at Brisbane Roofing Solutions to discuss what options are possible to remove it from your roof!