Knowledge Hub / Question
Why is there black mould along the ridges of my white Colorbond roof?
Answered by Luke at Westside Roof Cleaning & Soft Wash, with more than 12 years on Perth roofs.
Black streaks along the ridges, hips and edges of light Colorbond roofs are usually mould and algae that grow where moisture, dust and organic matter collect. It’s very common on Surfmist and other light colours. A soft wash removes it without damaging the paint.
Why it starts on the ridges
Ridges, hips and capping edges trap dust and leaf matter, and dew sits there longer in the mornings. That’s the perfect spot for mould to start. On dark roofs it’s hard to see, but on white and light grey roofs it shows up quickly.
Is it damaging the roof?
Left long enough, organic growth holds moisture against the paint and can shorten the life of the finish. It also makes the roof look older than it is.
How to remove it
Avoid scrubbing or high pressure, which can mark the paint. A soft wash breaks down the mould so it rinses away. This even works on roofs only two or three years old. See our soft washing service.
Related services: Soft Washing · Roof Cleaning