What’s growing on my roof: moss, lichen, mould or algae?

Green, fluffy clumps are usually moss. Flat, crusty grey, white or orange spots are lichen. Black streaks and dark staining across tiles or along Colorbond ridges are normally mould or algae. All four are living growth, and all four are removed with a soft wash and a treatment that kills them at the root.

How to tell them apart

• Moss grows in soft green clumps, usually on the shady side of the roof, in the gaps between tiles and along the bottom edges where water sits. It holds moisture like a sponge.
• Lichen looks like flat, crusty circles that are grey, white, yellow or orange. It grips the tile surface tightly and is very common on older terracotta and concrete tiles around Perth.
• Mould and algae show up as black or dark green streaks and patches. On light-coloured Colorbond you will often see it first along the ridges, hips and edges.

Why it matters

None of these are just cosmetic. Moss and lichen trap water against the roof, break down the surface of tiles over time, weaken mortar and capping, and wash debris into gutters. Dark growth also makes your roof absorb more heat in summer.

How we remove it

Scrubbing or blasting only removes what you can see. We soft wash the roof with a treatment that kills the growth, including the roots that sit in the pores of the tile, then rinse it off. Where you want longer-lasting results we apply a moss prevention treatment to slow regrowth.

Not sure what you have? Send us a photo when you request a quote and Luke will tell you straight.

Related services: Moss Prevention Cleaning · Roof Cleaning · Soft Washing