/ Field knowledge · IMC 801.8
“Cap by contractor” is not a detail.
When the old appliance comes out, its chimney or vent opening does not take care of itself. Abandoned inlets have to be closed by an approved method — not “cap by contractor.”
Educational 2024 International Mechanical Code (IMC) 801.8 from Daily Code Talk. Confirm the adopted edition. Distinct from existing chimney reuse (801.18). Gas-fired appliances also follow the fuel-gas code. This is not a flue design.
- Trigger: appliance removed, relocated, converted to direct-vent or electric, or an old connector demolished. The opening that is left behind has to be closed by an approved method, with a material compatible with the chimney or vent still in service.
- Show connector removal and the closure together. An appliance schedule that lists removals with no matching abandonment note is incomplete.
- A multi-appliance chimney where one unit is replaced and an old tie-in is never traced is the usual miss. That leftover opening undermines draft on the remaining appliances and can be a fire-separation gap.
On the set: demolition / vent-abandonment notes on the mechanical cover sheet, existing appliance and chimney locations, a closure detail, and coordination with 801.18 if the chimney stays in service.
“Cap by contractor” is not a detail
Ask where the old appliance used to connect — not only where the new one connects. Common vents and multi-story chimneys escalate: closing one opening can change draft for whatever is still firing.
Source: Daily Code Talk — IMC 801.8 · reuse: 801.18 four gates · tool: Where did the old appliance connect? · factory-built: 805.
What to send
What is coming out, photos of the chimney and every visible connector, whether another appliance stays on that chimney, and the new appliance cut sheet.
If the old water heater or furnace is coming out
Send the photos and the demolition note. Masterbuild will say whether 801.8 is just a closure detail — or the remaining chimney still has to pass 801.18.
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 801.8 education from Daily Code Talk — not a closure specification. Gas appliances follow the fuel-gas code. This page is not legal advice.