Short answer: Yes. High pressure can crack terracotta, strip the surface of worn concrete tiles, and push water under laps and ridges. The safer method for most tile roofs is a low-pressure soft wash with biocide, which kills moss and lichen instead of blasting it off. Roof cleaning starts from $490 ex GST.
How high pressure damages tiles
- Terracotta can crack or chip, especially older tiles that are already brittle
- Worn concrete tiles lose their surface, which makes them more porous and quicker to grow moss again
- Water forced under tile laps and ridge caps can end up in the roof space
- Walking a wet roof with a heavy hose risks cracking tiles underfoot
The safer way: soft wash and biocide
Moss and lichen have roots in the tile surface. Blasting them off at high pressure takes the surface with them. A biocide kills the growth at the root, and a low-pressure wash rinses it away.
The biocide keeps working after we leave, so regrowth is slower than with a plain wash.
Terracotta vs concrete vs metal
Terracotta is the most fragile when old, so it gets the gentlest treatment. Concrete tiles are tougher but their coating wears with age. Metal roofs do not crack, but high pressure can damage the paint finish and seals around fixings.
We match the method to the surface. That is the whole point of looking before we start.
Signs your roof needs more than a clean
If we see these on the inspection, a clean alone will not fix the problem, and we will say so:
- Crumbling mortar on ridges or chunks of it in the gutter
- Cracked, slipped or missing tiles
- Water stains on ceilings after rain
- Bare, chalky tiles where the old coating has worn through
What roof cleaning costs in Sydney
Roof cleaning and biocide treatment starts from $490 ex GST. Roof size, pitch, access and how much growth there is set the final price, confirmed after a free inspection.
Not sure what your roof needs? We inspect for free and tell you straight, including when a cheaper fix is enough.
Book a free inspection