Thread: Code ref for supporting tall vent pipes.

I have an HVAC guy wanting to argue about needing support for a furnace vent pipe that is rising about 10 ft high out of the roof to rise above an adjacent roof structure. I said the pipe needed support and he does not think it does. I do not have a code reference but would like to have one. Pic is deceptive as the pipe at the right is much taller than it looks in this picture. Thanks

From the 2012 IRC:
- G2426.5 (502.5) Installation.
- - Vent systems shall be sized, installed and terminated in accordance with the vent and appliance manufacturer’s installation instructions and Section G2427.
- G2426.6 (502.6) Support of vents.
- - All portions of vents shall be adequately supported for the design and weight of the materials employed.

G2427.6.9 (503.6.11) Support of gas vents.
- Gas vents shall be supported and spaced in accordance with the manufacturer’s installation instructions.


G2427.10.9 (503.10.9) Support.
- A vent connector shall be supported for the design and weight of the material employed to maintain clearances and prevent physical damage and separation of joints.

Of course, then there is trying to the manufacturer's instructions and what they specify for supporting the vent above the roof,

Originally Posted by Jerry Peck

From the 2012 IRC:
- G2426.5 (502.5) Installation.
- - Vent systems shall be sized, installed and terminated in accordance with the vent and appliance manufacturer’s installation instructions and Section G2427.
- G2426.6 (502.6) Support of vents.
- - All portions of vents shall be adequately supported for the design and weight of the materials employed.

G2427.6.9 (503.6.11) Support of gas vents.
- Gas vents shall be supported and spaced in accordance with the manufacturer’s installation instructions.


G2427.10.9 (503.10.9) Support.
- A vent connector shall be supported for the design and weight of the material employed to maintain clearances and prevent physical damage and separation of joints.

Of course, then there is trying to the manufacturer's instructions and what they specify for supporting the vent above the roof,

Thanks Jerry. Yeh, I am not doing that. I have always remembered any vent such as these over 5ft above the roof should be supported.

As a POI, it hasn't been uncommon for buyers, sellers and contractors to complain 'oh that picky inspector, support smupport, no big deal, whatever, blah, blah,'. Buyer also gets push back on the lack of proper support and backs down, figures oh whatever.
You may want to include the potential leak concerns in the report. This can be very helpful in getting the issue properly resolved. Buyer's tend to understand 'potential roof leak' better than 'lack of support'. Of course they don't want their roof to leak and demand either a fix or credit.
Leak issue of course being the swaying pipe breaking the caulk joint or widening out the collar.

In addition to the code references, the 5 foot rule is a good rule of thumb. Remember, it isn't just the whole stack but all those joints. What it usually forgotten is the need for support in the attic in three axis: vertical plus two intersecting horizontal planes. Failure to properly support can stress joints, especially the gores in elbows causing them to blow apart. Tall unprotected vents and chimneys run too cold. They will suffer from weak draft, condensation and sooting with wood. Then there is the leak issue as Marcus pointed out. If you need a vent that tall, it should be encased and supported in a chase.