Pressure washing the roof? Good or bad?

[dar636]

Cedar shakes, lots of PNW pine needles in the grooves. No, or at least not much moss.

I do not know the age of the roofing material, always figured it was close to needing replacement but would like to go another year or two. I had alos heard that pressure washing the roof will cause more problems than it solves.

Any experience out there?

[yetibone]

Don't do it. The stuff you're going to wash off could be what's keeping the roof from leaking right now.

[jorian]

Originally Posted by yetibone

don't do it. The stuff you're going to wash off could be what's keeping the roof from leaking right now.

+1

[azasadny]

Yep, don't do it!

[Dantilla]

Here in the Seattle area, cedar roofs fill with gunk, which holds significant moisture against to shakes, promoting rot. Once clogged, the roof will never dry out.

Moss kills roofs.

Even though I do lots of pressure washing myself, I have a pro come every two or three years to clean my cedar roof and spray it with the preservative that makes it look nearly new again.

In most areas of the country, the climate is dry enough that the wind will blow most of the crud off the roof. Here in the Northwest, junk will accumulate until the entire roof is covered in moss.

There is a specific way to clean cedar roofs. The wand must stay a good distance away from the cedar, and must be kept moving constantly. Can't just start at one end and blow it off like a sidewalk.

[Zeke]

I have a house I take care of for a wealthy old gent and it has shakes and city pine trees nearby. The wind blows the needles onto the roof. They interlock and collect other leaves. In some areas there will be these little beaver dams. This must be cleaned off.

What I do is use the PW with the stream at an angle almost parallel to the roof. I don't try to "clean" the shingles, just get the debris off the roof, especially the valleys.