/ Field knowledge · IMC 801.11
“It looks unused” is not a dedicated flue.
A solid-fuel appliance or fireplace cannot share a chimney passageway that is already venting another appliance — fuel-fired or otherwise. “It looks unused” is not a dedicated flue.
Educational 2024 International Mechanical Code (IMC) 801.11 from Daily Code Talk. Confirm the adopted edition. Distinct from existing chimney reuse (801.18) and abandoned openings (801.8). This is not a flue design.
- Wood stoves, fireplaces, pellet appliances, coal-burning appliances, and similar solid-fuel equipment need their own compliant, dedicated chimney passageway.
- Do not tie into a flue already serving a water heater, boiler, furnace, fireplace, or any other combustion appliance. Draft, temperature, soot/creosote, and cleaning needs are different — that is why mixing them in one passageway is the risk.
- On existing buildings, “dedicated chimney” is a claim that needs verification. Trace the full chimney, including historical tie-ins, before accepting it for a new solid-fuel appliance.
On the set: every appliance connected to that passageway (not only the new one), dedicated flue path, liner, connector, cleanout, and termination. A plan that shows only the new connection, with no statement about what else uses that chimney, is incomplete.
Only one appliance is visible today
The recurring gap is an existing chimney assumed dedicated because only one appliance is currently visible, without checking whether an old tie-in from a removed appliance still exists. Pair this with 801.8 closure and 801.18 four gates.
Source: Daily Code Talk — IMC 801.11 · tool: Dedicated-flue screen · 3:1 cap: 801.7 · existing: 801.18 · abandoned: 801.8 · multistory: 801.19.
What to send
What is being added (fireplace, wood stove, pellet), photos of the chimney and every visible connector, and what else — if anything — still uses that flue.
If a wood stove or fireplace is tying into an existing chimney
Send the photos. Masterbuild will say whether 801.11 even has a dedicated passageway — or 801.8 still has an old opening to close.
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 801.11 education from Daily Code Talk — not a flue design. This page is not legal advice.