/ Field knowledge · IMC 801.18.2
A sweeping invoice is not a reuse decision.
An existing chimney can look serviceable from the room or roof and still fail internally. Cleaning is not proof the liner is continuous and sound. The full path — connector inlet through liner or vent wall to the termination — has to be free of obstructions and combustible deposits, and free of cracks, gaps, and perforations that would let gases, moisture, or creosote escape.
Educational 2024 International Mechanical Code (IMC) 801.18.2 from Daily Code Talk. Confirm the adopted edition. Distinct from the 801.18 four gates and liner compatibility (801.15–801.16). Gas-fired reuse follows the adopted fuel-gas code, not IMC 801 alone. This is not a chimney inspection.
- The flue-gas passageway must be free of obstructions and combustible deposits. A passageway previously used for solid- or liquid-fuel, or a fireplace, must be cleaned. Cleaning and continuity are separate questions.
- The flue liner, chimney inner wall, or vent inner wall must be continuous and free of cracks, gaps, perforations, damage, or deterioration.
- Where an oil-fired appliance connects to existing masonry, the chimney flue must be repaired or relined in accordance with NFPA 31.
On the set: prior fuel use, inspection and cleaning scope, evidence returned, defects mapped, repair/reline/replace/reject disposition, then sizing, cleanout, clearance, and listing rechecked. Do not accept a chimney from an exterior-only look or a generic “existing to remain” note. Do not treat a sweeping invoice as acceptance.
Swept before replacement — cracked clay liner never addressed
Deposits are gone; gases, moisture, or creosote can still leak into concealed construction. Escalate unknown prior fuel, inaccessible offsets, incomplete full-length evidence, odor or spillage history, and oil-fired masonry without an NFPA 31 repair or relining basis.
Source: Daily Code Talk — IMC 801.18.2 · tool: Passageway screen · 801.18: four gates · oil: NFPA 31 · clearance: 801.18.4.
What to send
Prior fuel if known, photos of the interior if you have them, and whether anyone has a cleaning invoice being treated as the reuse decision.
If the chimney was swept and the liner was never mapped
Send the photos. Masterbuild will say whether 801.18.2 still has no continuity evidence — or 801.18.4 still has no clearance trace.
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 801.18.2 education from Daily Code Talk — not a chimney inspection or liner design. This page is not legal advice.