Does pressure cleaning harm a roof?
It definitely can, as if done incorrectly i.e. wrong equipment, wrong pressure, it will remove a layer of the tile surface, which reduces the life expectancy of the tile.
Done properly (using a rotary cleaner, with the correct nozzles and pressure) the loss of the fines from the tile surface is minimised.
When pressure cleaning a roof it is essential that the person doing the cleaning does NOT use a hand held lance or wand (except possibly for valleys, gullys and verges), as the control of the water jet is not good enough and it is entirely possible that water could be forced under the tile and into the roof space.
As said already, the ONLY way to pressure wash a roof correctly is by using a rotary cleaner, controlled from the ridge, this achieves two main things, the application of high pressure water on to the roof surface is done at a controlled angle (ideally at about a 70 degree angle from the surface) which helps prevent water ingress, reduces damage caused by high pressure nozzles hitting the surface at 90 degrees, and no one needs to tramp about all over your roof, which can cause more harm than any pressure washer ever could!
Posted in: Roof cleaning