Whether the 8 foot rule (NFPA) or the 10 foot rule(image supplied by most manufacturers) applies, the OP stated that the side wall was only 2.5 feet away.
The termination should either penetrate further up the roof line so it is 8ft. (or 10 feet) away from the wall or extend it above the upper roof The added issue is the operable window, though the OP still hasn’t told us how close it was.
If it’s less than 8 foot from the side wall then it has to be extended to two foot over the roof. I believe this has to do with wind pressure blowing over the roof can upset the draft of the vent.
Right. But is that an InterNACHI illustration?
What image? Please send me the link to the image in InterNACHI’s gallery that needs to be “changed to be more accurate.”
Thought so but maybe ask Richard…
What image? Please send me the link to the image in InterNACHI’s gallery that needs to be “changed to be more accurate.”
Again…
No, it is not an InterNACHI image. It is a common image that is often included in multiple manufacturers installation instructions. I am not aware of an InterNACHI image that depicts this particular situation.
What Larry and Martin may be referring to is the “one size fits all” statement that was in the link that @ryoung7 posted, which is inaccurate and misleading.
Thank you, Richard.
This could be changed to be more accurate, :
Type B and Type L Vent Inspection - InterNACHI®
Ah, Nick’s article. I’ll take a closer look. Thank you.
Yes. I like this one. I’m looking for the one that needs to be “changed to be more accurate.” Thanks.
For my own clarification would “anything” include things like a sewer vent pipe? Yes i realize a vent pipe is a “thing”. However I can see major pushback for calling a 2" pipe causing major ventilation issues. The verbage of “anything” is a bit of a question for me.
Based upon the diagram that’s now in this thread I can use that to aid in better describing to my clients roof and walls barriers. I’ve never located that diagram before. Thanks to all.
I’ve pointed out what I was referring and the snarky-ness doesn’t become you…at least, I think.
Me either. I would have posted it instead of my original comments and could have avoided the back and forth misunderstanding with Larry. 
I’m glad that I found this thread as I came across the same section and it doesn’t seem to clearly define the gas vent termination rules. On one hand the course material says that vents need to only be 12" in height on roof slopes Flat to 6/12, then just after that it will say, “All metal vents must terminate at least 2 feet above the roof surface and anything within 10 feet of the vent, such as the crest of a roof ridge.” So to clarify, do all gas vents basically always need to be a min of 2’ high or does that rule only apply to L vent, and B Vent can be a min of 12" if there’s nothing close to them?
The Fuel-Gas Terminations section doesn’t make a distinction between L and B vents in the Slope to roof clearance chart, but later there is a chapter that says this if L vents: “Type L venting systems should terminate with a listed and labeled cap at least 2 feet above the roof and at least 2 feet above any portion of the building within 10 feet. This is known as the Type L Vent 2-2-10 Rule.” which appears to be in contrast to the Slope to roof clearance chart.
If anyone can help clarify this, that would be appreciated. Thanks - Matt
Which clearance chart? Is there a Type L Slope to roof clearance chart? If so, please post it so it can be corrected.
Hi, thank you for the response. The area of the course that I’m referring to is below:
How to Inspect Fireplaces, Stoves, and Chimneys Course => Chapter 3 => Fuel-Gas Termination. "Gas vents that are 12 inches or less in size and located at least 8 feet from a vertical wall or similar structure should terminate above the roof in accordance with the Gas Vent Terminations table below.
Gas Vent Terminations
Minimum Height in Feet (& in Meters)
flat to 6/12 : 1 (0.30)
That chart( and the page) doesn’t specify Type B or L, it just says “Gas Vents” which would imply all types.
At the Top of the page is says, “For example, vent pipes terminating above roofs having a slope of up to 6:12 need to be only 1 foot high.” Should this say, " For example, type B vent pipes terminating…" because that sentence is in contrast to the Type L 2-2-10 rule?
Thanks for the help in clarifying this to me.
The height difference has nothing to do with the vent type, it has to do with the appliance type. 503.6.5 deals with venting fuel-gas appliances and 802.5 deals with venting fuel-fired appliances other than gas-fired.
The training materials are wrong and the advice is always the same, “get more training”, from training materials that are wrong.
Yep, @mharrington7. We’ll take a look at adding some language to help clarify that this is on the Fuel-Gas Termination page of the course. InterNACHI® - International Association of Certified Home Inspectors. The Gas Vent Termination Table in the course comes directly from 2021 IRC G2427.6.4 (503.6.5) Gas vent terminations. But I’ll take a closer look for inaccuracies or wrong advice.
