/ Field knowledge · IMC 802
Diameter is not a listing.
IMC 802: listed vents are a system. Diameter is not a listing. Type L / pellet vents are UL 641 and only for appliances listed for that vent.
Educational 2024 IMC 802. Confirm adopted edition and manufacturer instructions. This is not a vent sizing. Distinct from 805 factory-built chimneys and 806 metal chimneys.
- 802.1 / 802.2: listed and labeled. Type L and pellet vents: UL 641, used only with appliances listed for that vent type.
- 802.3 / 802.4: size, install, and terminate per both the appliance and vent manufacturer. Type L: listed cap per the vent manufacturer.
- 802.5 Type L termination: at least 2 ft above the highest point of the roof penetration AND at least 2 ft higher than any building portion within 10 ft. Both conditions.
- 802.6: generally at least 5 ft of vertical height above the highest connected appliance flue collar. Exceptions: direct-vent, listed outdoor appliances with integral venting, pellet vents per listing/instructions.
- 802.7 support the full path. 802.8 insulation shield at insulated assemblies; in attics the shield extends at least 2 in above the insulation and is secured. 802.9: doors cannot swing within 12 in horizontally of a vent terminal — doorstops/closers do not create the clearance.
Doorstop as clearance
Trace one vent, on one appliance, from the flue collar to the cap. Listing, 2/10 roof, 5 ft height, shield, and door swing are one chain. A missing attic shield fails inspection after the vent is in.
Source: DCT 802 · cap: 802.3–802.4 · 805: factory-built · 806: metal chimneys.
What to send
Appliance listing, vent type if known, roof plan with nearby ridges/walls, and door swings at wall terminals.
If the B-vent was picked by diameter
Send the appliance listing. Masterbuild will say whether 802 even allows that vent — or the 2/10 roof and the door swing were never checked.
Send Project Background+1 (786) 398-6940 · osmany.portal@masterbuildconsulting.com
Masterbuild provides engineering services under a written scope. Nothing on this page is project-specific engineering advice, a code interpretation for your project, or a representation about permit approval.