Roof vent, flue, & chimney height

(Steve Osborne, 70001310) #1

chimney 3-2-10-rule.jpg

Vent pipes on roof.jpg

typebterminationchart.jpg

Can someone please explain the difference in these pictures?? I understand chimney height requirements but am confused about fuel vents and flue pipes minimum height.
One picture shows 3 feet, one says 2 feet, and the chart shows 1 foot.
Also chapter 3 of the inspecting roofing course says “It is a common mistake to apply chimney termination-height requirements (3-2-10 rule) to fuel vents, which cause vents to extend above roofs much higher than needed.” The rules seems conflicting. Any help would be appreciated.

chimney 3-2-10-rule.jpg

chimney 3-2-10-rule.jpg

Vent pipes on roof.jpg

(Christopher Foley) #2

Yes. Confusing at first but makes sense somewhat.
MASONRY chimneys have the 3-2 -10 rule
WOOD burning metal flues also have the same rule
B VENT - aka double wall metal flue for gas appliances (boilers etc) actually have 2 rules based on that last table foto. There are 2 tables based on width if the B vent used. I am on my phone , i will try and post both tables later on or if someone else can do it for me beforehand.
It comes down to 3 different types of ‘chimneys’ having their own rules

(Christopher Foley) #3

Vent caps larger than 12" must be located at least 2 feet above the highest point and 2 feet higher than any portion of the building within a horizontal distance of 10 feet.

Vent caps 12" and smaller may terminate a distance above the roof if 8 feet or more away from a vertical surface as your table shows

(Steve Osborne, 70001310) #4

OK, thank you Chris. That helps.