Gas vent loactionin proximity to roof vent

Does anybody know of any kind of ruling about the gas vent in proximity to a roof vent I’ve never seen anything like this and it seems improper to me. Before anybody else this is a 6/12 roof pitch.

What does it vent? You have the model number? Does the manufacturer provide direction?

Then there is this which is helpful. But, the manufacturer is the best source 1st, because we are not code inspectors.

Gas furnace and gas water heater

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The link I gave you should provide the guidance you need. And, I do think the top of the roof vent is the height from which the vent should be measured.

I’ve run across this a few times and it’s always kind of a mess as to where you are measuring from. The manufacturers usually just give a measurement and don’t specify if it’s centerline, top, back, closest point, etc. IMO, if it’s so close that those things matter it’s too close but I’m just a lowly HI in the whole grand scheme of things. Fwiw, that installation just looks dumb but that doesn’t always = wrong.

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I would feel comfortable calling this out. I just have not seen the attic vent so close before.


That’s a chimney though with sparks and whatnot. This is just a flue so I think it’s different. I remember one similar to OP right next to a bedroom window and it turned out to be okay. I was amazed. I was equal parts worried about fumes and the vent blocking egress out of the bedroom window!

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Edit: The illustration appears to be for both. Though, I call this a flue…I think it is interchanged in this illustration.


Your illustration is for a chimney. Gas appliance vents have completely different guidelines.

FLAT TO 7/12 _______________1.0 FEET*
OVER 7/12 TO 8/12___________1.5 FEET
OVER 8/12 TO 9/12___________2.0 FEET
OVER 9/12 TO 10/12__________2.5 FEET
OVER 10/12 TO 11/12_________3.25 FEET
OVER 11/12 TO 12/12_________4.0 FEET
OVER 12/12 TO 14/12_________5.0 FEET
OVER 14/12 TO 16/12_________6.0 FEET
OVER 16/12 TO 18/12_________7.0 FEET
OVER 18/12 TO 20/12_________7.5 FEET
OVER 20/12 TO 21/12_________8.0 FEET


My illustration mentions both.

And then we have local jurisdictions.

And then we have 2018 IRC (see illustration) Which is nearly identical to yours.


At some point, you will have to make a judgement call because of the passive roof vent.

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