Yeah, but They Use the “Low Pressure, High Volume” Method
Oh pulleeeze! We have been restoring and maintaining cedar roofs since 1991 and that is a reply we’ve started hearing in the last few years. The reason people are being told that is simple. The pressure washers are tired of hearing the person on the other end of the phone say, “I don’t want my roof pressure washed.” I’m sure you’ve heard horror stories of pressure washing damage and leaks caused. If not, call me and I can tell you a bunch of them. Rest assured, the ones you’ve heard and the ones I can tell you are all true.
Experience Is Key
I am the first to acknowledge that there are some good, conscientious power washers out there who are careful and know what they are doing. There are a lot more incompetent and/or inexperienced people using the machines. But whoever ends up on your roof with one, there is no denying the simple physics of the process: There is a person up there with a water gun which is putting out anywhere from 6 to 30+ gallons per minute of water under 1500 (to the pressure washers, that’s ‘Low Pressure’) to 3500 lbs. per square inch of pressure at point-blank range all day long. Your garden hose is only about 100 psi and it will peel paint! (The amount of traffic on the roof needed to do so is a separate but relevant issue) After you’ve heard all the claims and “pitches” (mine and theirs both), the simple fact is this: these roofs are not built for that – they are built to be rained on.