/ Field knowledge · IMC 802.3–802.4
A generic cap is not the listed Type L system.
The vent manufacturer and the appliance manufacturer both belong in the design basis. Where they differ, resolve it on the drawings — not in the field. Type L vents terminate with a listed and labeled cap that matches that vent type and diameter. A generic cap is not the listed system.
Educational 2024 International Mechanical Code (IMC) 802.3 and 802.4 from Daily Code Talk. Confirm the adopted edition. Distinct from vent listing (802.1–802.2) and termination heights (802.5–802.6). This is not a cap selection.
- 802.3: size, install, and terminate per both the vent manufacturer’s installation instructions and the appliance manufacturer’s installation instructions. Size, type, offsets, routing, slope, joints, support spacing, clearance, penetrations, and termination configuration — all of it.
- The appliance manufacturer establishes the acceptable venting method. The vent manufacturer establishes how the listed system is assembled, supported, routed, and terminated.
- 802.4: Type L vents terminate with a listed and labeled cap installed per the vent manufacturer. The cap is part of the listed system — compatible with vent type, diameter, and installation condition.
On the set: vent size, route, support, and termination together on the same detail. “Install per manufacturer” is not the only venting information. A roof plan with a vent and no cap specified leaves a listed-system component undocumented.
Vent-manufacturer offsets, appliance-manufacturer more restrictive
Or the reverse. The conflict is left to field interpretation. Escalations: either manufacturer’s limits exceeded, missing or unlisted caps, support spacing not documented against the manufacturer.
Source: Daily Code Talk — IMC 802.3–802.4 · listing: 802.1–802.2 · heights: 802.5–802.6 · door swing: 802.9.
What to send
Appliance and vent cut sheets (instructions if you have them), vent type and diameter, and whether a listed Type L cap is specified.
If the roof plan shows a vent and no cap
Send the vent type and diameter. Masterbuild will say whether 802.4 still has no listed cap — or 802.3 still has two manufacturer instruction sets that disagree.
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. Confirm the adopted edition. This page is 2024 IMC 802.3–802.4 education from Daily Code Talk — not a cap specification. This page is not legal advice.