/ Field knowledge · IMC 803.10.4
A 6-inch air gap is not the pass-through assembly.
A chimney connector cannot pass through a floor or a ceiling. Through a combustible wall it needs a listed pass-through or a named Table 803.10.4 system (A, B, C, or D). A clearance number without the system name is not the assembly.
Educational 2024 International Mechanical Code (IMC) 803.10.4 from Daily Code Talk. Confirm the adopted edition. Distinct from the broader connector hub (IMC 803) and clearance reduction (308). This is not a connector design.
- Connectors cannot pass through floors, ceilings, or fire-resistance-rated wall assemblies.
- Domestic-type appliances: connectors cannot pass through combustible walls or partitions unless an approved method is used. Three paths: a connector listed for wall pass-through and installed per the manufacturer; a listed wall pass-through device; or a connector not larger than 10 inches using Table 803.10.4.
- Table 803.10.4 has four systems — A (12-inch clearance), B (9-inch), C (6-inch), D (2-inch). Each has its own liner, insulation, support, airspace, connector construction, and attachment. The clearance dimension alone does not establish compliance.
- Noncombustible penetration seals. Listed clearances and thicknesses are minimums. Concealed metal exposed to flue gases has to resist corrosion and temperatures up to 1,800°F. Except for System B, the connector extends to the inner face of the flue liner.
On the set: wall type and fire-resistance rating at every pass-through, which of the three paths, and — if the table — which System A–D with its liner and insulation. Coordinate with architectural / life-safety sheets.
A 6-inch air gap is not System C
Citing a Table 803.10.4 clearance without naming the system leaves liner, insulation, and support unverifiable. Floor and ceiling pass-throughs are not a field option. Improvised combustible-wall penetrations are an ignition and concealed-spread risk.
Source: Daily Code Talk — IMC 803.10.4 · tool: Pass-through screen · connectors: IMC 803 · shields: 802.8.
What to send
Connector size, wall / floor / ceiling construction and rating, and whether a listed pass-through or a Table 803.10.4 system is assumed.
If the connector ducks through the wall
Send the section and the wall type. Masterbuild will say whether 803.10.4 even has a path — or the connector has to stay in the room.
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. Table 803.10.4 System A–D clearances and the 10-inch / 1,800°F figures are 2024 IMC education from Daily Code Talk — not a pass-through design. This page is not legal advice.