/ Field knowledge · IMC 803.10.6
18 inches is not every connector.
A connector that passes every other IMC 803 check still fails if clearance to combustibles was never walked along the full route. Table 803.10.6 is the starting minimum. If the appliance listing says a different clearance, the labeled clearance governs. Reductions only under IMC 308 — not improvised sheet metal.
Educational 2024 International Mechanical Code (IMC) 803.10.6 from Daily Code Talk. Confirm the adopted edition. Distinct from wall pass-through (803.10.4) and clearance reduction (308). This is not a connector design.
- Table 803.10.6 key minimums from Daily Code Talk: 18 inches — domestic electric and oil incinerators; 18 inches — domestic oil and solid-fuel appliances; 9 inches — oil appliances labeled for Type L venting; 18 inches — commercial and industrial low-heat oil and solid-fuel; 36 inches — medium-heat oil and solid-fuel; high-heat — determined by the code official.
- Do not assume 18 inches applies to every connector. Identify the appliance classification first.
- Clearance is three-dimensional along the full path — wood studs and joists, roof and floor framing, combustible finishes, casework, stored materials — not a single dimension at the appliance.
On the set: appliance type and venting basis on the schedule; the connector route against adjacent construction in plan and section. A compliant appliance location does not automatically mean the connector route is compliant.
The miss is usually before the chimney, not at the appliance
Insufficient clearance can pyrolyze wood, start a concealed fire, and fail inspection. Improvised sheet-metal wraps are not IMC 308. Hidden framing behind finishes still counts.
Source: Daily Code Talk — IMC 803.10.6 · tool: Clearance screen · pass-through: 803.10.4 · 308: clearance reduction.
What to send
Appliance type and listing (oil / solid-fuel / Type L / medium-heat), connector route in section, and whether a 308 reduction is assumed.
If the connector runs tight to wood
Send the section and the appliance type. Masterbuild will say which Table 803.10.6 row applies — or whether 308 is even on the table — before the route is boxed in.
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 803.10.6 inch figures are 2024 IMC education from Daily Code Talk — not a connector design. The labeled clearance governs when it differs. This page is not legal advice.