AskCodeMan

Too often I observe B-Vents installed out of plumb above the roof line. I find nothing in the IRC regarding this. Is there a standard one can refer to?

Hi Aaron,

Nothing specifically about that other than the various installation instructions and codes address 'vertical', 'horizontal slope 1/4" per foot' and 'offsets'.

I doubt the B vent sections above the roof are so far from 'vertical' that the 'offset' would create a problem within the allowances allowed within the code and/or manufacturer's installation instructions.

I'm not sure if the word "vertical" is used in the manufacturer's installation instructions, but the drawings I've seen show 'vertical' and 'offsets', thus pushing hard on the definition of "vertical" as meaning ... well ... "vertical" ... may be a losing battle.

Another point you could address is that the code requires Type B Gas vent to be terminated in accordance with the manufacturer's installation instructions, which includes the flashing, storm collar, etc., and maybe some wording in there would help.

Codes and manufacturer's installation instructions do not address, and cannot fix, "stupid".

Consider addressing the not-vertical-vent-above-the-roof from this aspect: the vent needs to be secured and supported to withstand the wind loads, and being as you 'know' the contractor installed the B-vent "vertically" at the time of installation, the only explanation left is that 'the wind must have blown it crooked', therefore it is simply a matter of adding proper supports and straps as necessary to support and secure the B-vent "vertically" ... just like when the installer first installed it.