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Community and Q&A

Best practices for minimizing roof penetrations?

Steve Knapp CZ 3A Georgia | Posted in Green Building Techniques on

My house will have a gable roof with standing seam metal roofing. I’d like to minimize the number of penetrations to reduce the potential for problems over the long term.

The house is two stories over a basement. It is all electric with a bath on each floor. I know some devices, such as the kitchen and bath fans, can be vented out the sidewalls. But it seems like the plumbing stack and radon system have to go through the roof. Are there best practices for these types of situations that will help to ensure that I’m not having a problem with water and air leakage? Even though the house doesn’t have a fireplace, would I want to consider a “false” chimney as a way to get everything vented above the ridge line? Or am I being too paranoid?

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

    A good roofer knows how to flash a plumbing vent. I think you should relax.

    If you live in snow country, however, it's always a good idea for most of your penetrations to be as close to your ridge as possible (so sliding ice doesn't cause problems).

  2. Steve Knapp CZ 3A Georgia | | #2

    Thanks, Martin.

    In Zone 3 there's not much of a snow problem. I'll take your advice and give it a rest for a while.

  3. Kevin Dickson, MSME | | #3

    Another reason to limit roof penetrations is for looks. Plumbing & radon vents can go out a gable or even a wall where it meets code.
    Junk on the roof can also compromise a big PV system.

  4. Ronnie Allen | | #4

    I am a roofer and I think it is great you are thinking about this. I think you could have more potential issues with the roofer flashing the false chimney than the pipes.

    The plumber gives me the general area for the vent and I cut the holes for them so the pipes land in the dead center of the panels. The plumbers have been great about minimizing projections through the roof by tieing in vents together where they can. The pipes are usually put on the back of the house, high to the ridge, like Martin stated, but not so high they can be seen from the front sticking up over the ridge. The are easy to seal to the roof and you should have no problem with leaks.

    If you end up with bath or kitchen fans through the roof they are a little more tricky as the ones the trades will provide to install are usually made for shingles. Getting these water-tight will depend on the quality of your roofer. To help with appearances of other needed vents or caps, I have them powder-coated to match the roof color.

  5. Steve Knapp CZ 3A Georgia | | #5

    Hi Ronnie and Kevin.

    Thanks so much for your input on this issue. With your responses and Martin's, I now feel more confident that this portion of the construction process can be handled without any issues.

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