2/10 rule apply?

Does the 2ft above surface within 10ft rule apply on B vents at the roof??
All I can find for B vents is (2ft above VERT. surface within 8ft) IRC [2426.6.5]

061017-01 023.jpg

I was wondering the same on a similar encounter. How about this one?

Nice one Joseph,… are the walls within 8ft of the vent. I would imagine the IRC I quoted above would apply???

I’ve been taught that the 2/10 rule applies to fireplace chimney’s/flu’s.It’s also been my experience that it is for good reason.Fireplaces do not draw as well ,or sometimes not at all, if the 2/10 rule is not implemented.
I’ve not heard of 2/10 applying to “B” vents.

Cheremie is correct. The 3/2/10 rule applies to fireplace chimneys and other “solid-fuel” burning chimney/vent systems.

The B-vents, for gas appliances, can be as short as 1 foot, depending on the slope of the roof, or at least 2 feet above the roofline of any vertical surface within 8 feet of the vent.

Oil burning appliance vents must terminate at least 2 feet above the roof or roofline of any vertical surface within 10 feet of the vent.

Now I’m confused. . .


Manufacturer suggests 1 foot clearance for Natural Vent Gas fired in this application.

HA!! Thanks Jeff,… :shock: :mrgreen: Thats why its confusing, and the reason for my post. The B vent rule is 2ft above if within 8ft of a “vertical” wall. Im assuming a pitch roof plane is not a vertical wall (duh) Soooo in this case (my picture above) its fine. Im confused too, but the 2/10 rule only for fireplaces I get and makes sence.

I think yours is okay Peter. Joes, on the other hand, does not comply.

Jeff, I’m with you (I think) :wink:



Additionally, this may help:


Code Check Plumbing 2004 has a great illustration of this code.
Don’t think I can post a copy here due to current copyright laws.
If you have a copy look at page 24 (lower right hand corner).