Pressure Washer Damage

Roofing damage in progress:

I was at an inspection, talking to my client about his plan to add a bathroom to a 2nd floor area, when out of the corner of my eye... "I am sorry Mark, but would you mind if I ran downstairs to get my camera?" I didn't wait for an answer. I needed a photo of this pressure washer damage "in action".

class="caption">Roof Damage in Progress!

Well, Mark was a nice guy and I needed a picture of this crime. The roof in question (see above) had been in fine shape (just a few minutes earlier). It had a little moss on it, some debris, but nothing that couldn't be solved with a garden blower or a soft broom and a moss control agent.

Enter the pressure washer, and what a pressure washer it was. Just take a close look at the stream of 2400 PSI water being directed at the roof! Mark was also looking at this crime and spotted the fact that some of the roof tabs were being visibly lifted by the force of the water! (a video clip would work here). This fine roof was being destroyed! Granules were being washed off the shingles by the pound! Roofing tabs were being loosened and the self sealing adhesive broken! The roof was loosing years of life by the minute! (ok, ok, I will calm down.)

So, what's wrong with pressure washing composition and most other types of roofs?

  • Composition roofing is a relatively soft material. Any abrasive action removes the protective granular surface, breaks the bond between the shingles and damages the fabric of the material.
  • At best pressure washing only does some damage to the roofing, at worst it destroys perfectly good roofing.
  • When pressure washing removes moss and debris from the roof, it also removes some of the roofing material.
  • If there is a lot of moss on the roof, the moss has already done some damage to the roofing material, the roofing material has already lost some of its integrity. Killing the moss with a moss control agent reduces further damage but leaves the roofing in place. Pressure washing removes the moss and the partially damaged roofing.
  • The bottom line is: pressure washing a roof will shorten the life of the roofing. Pressure washing removes moss, but also part of the roofing.

Do pressure washers have any value? Yes! for deck maintenance, preparing siding for paint, and to clean concrete driveways. But even in such applications, keep in mind that pressure washers are very strong tools and can damage wood and other surfaces. They are used in logging operations to remove bark from trees!