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Community and Q&A

Plumbing vents exiting ridge cap

R Miller | Posted in Building Code Questions on

Can’t seem to find anything in the code, easily missed though. I have a customer who wants a metal roof installed however they have had bad experiences with pipe flashings through the roof and don’t like the look of them. While I don’t care for the pipe boots, (for metal roofing), appearance they seem to work well.

Anyway, to the question… Is there anything code or common sense wise that says vents couldn’t go through the ridge cap? I know it wouldn’t look as good but, would limit water flowing over them.

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  1. User avatar GBA Editor
    Martin Holladay | | #1

    R. Mills,
    I don't think there is a code problem -- just an aesthetic problem.

    It's also a little more awkward to install the boot. Not impossible -- depending on the type of boot and the roof slopes -- just more awkward.

  2. R Miller | | #2

    We've been using the gray/red round ones on metal roofs and they are ugly but, I haven't found any thing that works as well and looks better. I've spent hours on google images, etc. looking for something and haven't had any luck. If we do it this way we are going to use a "flat" ridge, just a bend for the pitch, no steps or contours.

    We've seen many metal roofs over shingles that had the vents cut off in the attic, nothing through the metal! Dangerous as far as I'm concerned.

  3. Malcolm Taylor | | #3

    If you can get it to the ridge, could you get it to a gable end wall?

  4. R Miller | | #4

    Run it out gable and then up above roof. I honestly didn't think about that

  5. Nick Welch | | #5

    There's an old house near me that has what looks like a cast iron vent stack going up an outside wall of the house to above the roof.

    Found it on Google Maps street view:

    Looks funky but it works.

  6. Peter L | | #6

    In my area and for my build, code allows one to run the plumbing stack vent out the side of the wall of the home. This works better on 2-story homes. Just be sure to keep it away from any windows and code states it must be away from any windows/doors.

    The less roof penetrations or holes in the roof, the better. A vent stack in the roof is usually a source of air and water leaks. Whenever I had to deal with roof leaks, 90% of the time it was a roof penetration like a plumbing stack or bathroom vent.

  7. Malcolm Taylor | | #7

    As Peter says - most codes allow the vent to terminate on side wall without running it up to the roof level.

  8. Peter L | | #8

    I would stay away from those big box store rubber vent stack boots. I've seen a couple of those things melt after sitting in the summer sun. They must have used some cheap rubber that wasn't UV resistant and the black boot just soaked up the heat and melted in a molten goop. We found out it was leaking after a nice rainstorm made its way into the home due to the compromised seal.

    Plumbing stack vents out the side wall of the home is allowed per IRC. Proper slope and clearance must be met but it's done all the time. My design has ZERO roof penetrations. All bathroom venting goes out the side wall via a single HRV system vent. Plumbing vent stack goes out the side of the 2nd story gable wall.

    You can also utilize mechanical vents like STUDOR which help reduce or eliminate some of the plumbing stack vents:

  9. Leo Kloop | | #9

    I haven't penetrated a roof in 10 years ever since I read in the code book that you can run the vent out the gable. Inspectors actually really have a very positive reaction to this method. there are issues with how close you can be to an operable window.

  10. Richard McGrath | | #10

    Go the gable end route . There are even flat flashings available for this application that get placed right against the sheathing .

  11. R Miller | | #11

    I looked through the IRC, if you happen to know where it's at id appreciate the info. I don't have a hard copy handy.

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