Why we never use high pressure on roofs — and what we do instead

Ridge capping is bedded in mortar. High pressure erodes that mortar, and once it goes the caps lift in the next decent wind.

Water gets driven upward under the tile overlap. Tiles shed water flowing down, not water forced up at 3,000 PSI. That water ends up in the roof cavity, in insulation, and eventually on a ceiling.

Concrete tiles have a factory surface coating. Pressure strips it, which exposes the porous concrete underneath and makes future moss growth faster, not slower.

On Colorbond, pressure strips the protective coating and voids the manufacturer warranty.

Moss and lichen are living organisms with root structures. Pressure knocks off the visible growth and leaves the roots. That is why pressure-washed roofs regrow within twelve months.

Soft washing applies a biocide that kills the organism entirely. Dead growth then weathers off over the following weeks with normal rain.

A properly soft washed roof stays clear for three to five years. That is the actual difference, and it is why the method matters more than the price.

We apply the solution at low pressure across the whole roof, working in sections so nothing dries before it has worked.

Gutters get flushed afterwards, because the runoff carries a lot of dead growth.

The roof does not look finished the day we leave. It keeps improving for two to four weeks as the dead lichen weathers off. That surprises people, so we say it up front.