Of course some chemicals can harm your roof as well and the runoff could cause problems with your landscape or parts of your home.
Is pressure washing a roof bad.
If your house is made from a wood frame with any type of wood siding there is definitely a chance that pressure washing your house will launch water into the siding which can soak through wall cavities flooring wiring insulation and plaster.
The water pressure will remove the granules that are important for protecting your roof.
So why is power cleaning bad for your asphalt roof.
There is a chance that the pressurized water could damage your shingles.
Once you squeeze the trigger the powerful recoil on the spray wand can throw you off balance and off of a ladder.
Tempting as it might be to blast away unsightly moss and algae using a pressure washer to clean your roof is dangerous not to mention potentially damaging.
Pressure cleaning a roof when done properly using rotary cleaning equipment is safe cost effective and will not force water through or under tiles as the jet angle is controlled and always points away and down the roof rather than into or all over the place which is the case when blasting with a lance or wand is used.
After a good power washing the roof will look great but if too much pressure is used a significant chunk of the roofs life has just been removed it looks better though so imo using a power washer on a roof is a big no no people still do it though and the customer is happy because they don t know that their roof was damaged by the power washing.
For starters we never recommend.
Never pressure wash your roof if you have asphalt shingles.
Pressure washing is very effective but may be best for metal or concrete roofs.
It will also leave gouge marks in the lower layers leaving them more vulnerable to the elements.
Power washing a composition roof will remove the protective granular from the outer layer of the shingles leaving the shingles less protected from the sun and other harsh weather conditions.
Don t underestimate the power of these pressure washers.
Not to mention using a pressure washer from a high place is dangerous.