Thread: Plumbing Vent Roof Jack At Valley

Ordinarily I would blame a lazy or inattentive plumber for placing a plumbing vent so close to a roof valley. But in this case this was an existing vent that years later ended up too close to a valley that was created when a rear addition was built.

Anyway, the valley flashing was stepped and notched to accomodate the roof jack flashing. Does anyone see a problem with the flashing for the roof jack encroaching into the valley? What comments would you make?

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Bruce. I got this from Inspection News a while back. Just change chimney.

CHIMNEY IN VALLEY:
: There is supposed to be a 36" wide moisture barrier underlayment at all valleys, 18" to either side if installed correctly, Therefore no chimney(s), plumbing vent(s), or flue stack(s) should be placed within 18" of a valley. Penetrations to the moisture barrier may eventually leak and these areas will require further monitoring and sealant application if not relocated and installed correctly.

We went through this recently, and it depends on how valleys are done in your area. (That's what was decided here.)

Many areas install a 16" wide valley metal in the valley, which extend out from the center 8" to each side, stay outside that valley metal and there is no problem.

Other areas install a 36" wide roll down the center of the valley, which extends out 18" ...

I'm not sure that the flashing in your photo is even 8" out from the center of the valley, and that is the minimum distance to clear the valley metal.