Never pressure blast a tile roof (and what to do instead)

Somebody on the internet is running a turbo nozzle across a concrete tile roof right now, and the video looks incredible.

Here is what is actually happening.

## What high pressure does to a tile Concrete roof tiles have a factory-applied surface coating. High pressure strips it. Underneath is porous concrete, which holds moisture and gives moss and lichen a better foothold than they had before.

It also forces water sideways under the tiles, past the laps, and into the sarking or the ceiling. The customer discovers this three weeks later when the cornice stains.

And on an older roof, the pressure breaks tiles. Not always visibly, and not always immediately.

## What the growth actually is Lichen, moss and algae are organisms with roots into the surface. Blasting removes what you can see. The organism stays and returns within a year.

## The professional method Soft washing. A sodium hypochlorite solution at 3–6% depending on severity, applied at low pressure, allowed to dwell, then rinsed gently — or on some jobs, applied and left to weather off over the following weeks with the customer's agreement in writing.

The chemical kills the organism. That is why a soft washed roof stays clean for years rather than months.

## Before anyone goes up Roof work is work above two metres. That means fall protection and a safe work method statement — legal requirements, not suggestions. If you do not have height safety training, a rated harness and a suitable anchor, quote what you can reach from the ground and subcontract the rest.

And check the roof material. Asbestos cement sheeting must not be disturbed at all — it is a licensed removal task.

## The two things people forget 1. Disconnect or divert downpipes feeding a rainwater tank. Every time. 2. Quote the gutter clean with it. The gutters will be full of dead lichen afterwards, and it is a natural, honest upsell.

## The business case Roof cleans run $650 to $2,500. The margin is excellent. But the operators who last are the ones who say "that roof isn't safe for us to work on" when it is true. That sentence costs one job. The alternative costs the business.