Roofing Aftercare & Warranty

If you live in the tropics, your house is surrounded by trees or dense bush, or part of your roof is in shade for periods during the day, your roof may be susceptible to algae or mould growth. Algae and lichen can still grow on roofs south of the tropics, and commonly can occur on darker roofs, or if your roof is made from a harder surface like glazed terracotta tiles.

Other common roof issues that can be mistaken for algae and lichen, include soot, dust, windblown dirt, industrial or car pollution or kitchen exhaust build up that can collect on low sloping roofs, or roofs shaped to create uneven patterns of wind flow. Lighter coloured roofs can also appear to have lichen and algae growth, however while these roofs may be prone to algae or mould, due to their light colour they are more likely to show up dirt and dust build-up which could be collecting on the roof’s surface.

White or lighter coloured roofs are generally cooler than darker coloured roofs. Roofs that retain less heat can cause dew to condense more easily and stay damp for longer in the mornings, before the sun and wind is able to dry it. These damper conditions can both encourage more dust to remain on the roof and provide a micro-climate that is more suitable for algae, mould and lichen growth.

Other deposits that collect on your roof can encourage algae, mould and lichen growth. This could include pollen, tree resins, possum, bird or bat droppings as well as soot, dust, windblown dirt, industrial and automotive pollution and deposits from kitchen exhausts that may adhere to a membrane surface. Deposits will accumulate more easily where sections of the roof are shaded, have disrupted air flow (particularly in channels between ridges), remain damp for longer (again channels rather than ridges) or have underlying heat sinks (such as metal joists and beams).

Common areas that often show signs of early mould growth include noses of tiles where overhang can collect moisture that runs off the face of the tile and shades the area, which in turn slows down drying. It’s recommended these areas are checked regularly to catch signs of mould or algae growth early, before they develop further.

Washing your roof regularly to remove dirt or other substances that have built up can help stop growth of algae, mould and lichen.

The colour of your roof can also discourage mould and algae growth. Darker coloured roofs can heat up more quickly and may increase your roof’s temperature, promoting quicker drying of moisture that collects on its surface and discouraging mould growth.

Here are a few suggestions that may help improve the appearance of lighter roof membranes and help reduce algae and mould growth:

Allow more natural light to hit your roof by trimming back shady trees and surrounding foliage.

Avoid blowing leaf litter to minimise levels of dust and organic matter in the air that can settle on your roof.

Prevent possums, bats and birds from roosting nearby by clearing the area around your roof (subject to council approval).

Keep your gutters clean to encourage your drains to clear quickly following rain.

Take action early to discourage mould growth by considering applying cleaning solutions such as Wet & Forget®.

While chemicals such as bleach (dilute hypochlorite solutions) or sugar soap can be used to treat mould, applying harsh chemicals can risk damaging your roof’s membrane film. There are a range of other mould treatments on the market that claim to kill algae and mould without the addition of chemicals, however we recommend regularly cleaning your roof when safely accessible with a soft broom and a low foaming, biodegradable, general purpose cleaning solution.

In some cases, pressure washing may be needed to remove lichen from surfaces like glazed terracotta, concrete tiles or Colorbond®. When considering using pressure wash, be aware of potential to damage to any underlying coating. Before you start cleaning, it’s important to disconnect any downpipes to rainwater tanks before and rinse your roof thoroughly with potable water before reconnecting. For more information on collection of drinking water, see our Drinking Water Statement.

For further help and advice about chemical and non-chemical treatments for cleaning your roof, contact the Dulux Acratex Help & Advice team on 13 23 77.

Dulux Acratex roof membrane products have been developed and rated for exterior exposure to meet or exceed Australian standards, so you can rest assured knowing that your roof colour is protected with superior coverage.

Whilst the Dulux Acratex Roof Membrane has excellent colour durability, roof colour change is a natural process that happens slowly over time and some fading is expected with weathering. Roof chalking can sometimes occur and can be a reason why roof membranes fade or lose their colour intensity over time. Chalking is when acrylic binder breaks down under harsh sunlight and exposes some of the coating pigments on the surface. Washing your roof regularly will help to remove chalkiness and other materials that can collect on your roof and cause fading.

Growth of algae, mould and lichen can also contribute to colour change and is largely due to environmental factors, roof colour choice and the accumulation of dirt and pollution on your roof’s surface over time. Regularly maintaining your roof and removing any dirt build-up or other deposits that encourage these growths, will help keep your roof looking great for longer.