/ Field knowledge · IMC 803.8–803.9
“Galvanized” without a gage is not a connector spec.
A correct connector diameter with the wrong gage is still noncompliant. Identify material and thickness — “metal vent connector” is not enough. Vent-connector minimums (803.8) are not the chimney-connector tables (803.9). The hotter and larger the connector, the heavier the required construction.
Educational 2024 International Mechanical Code (IMC) 803.8 and 803.9 from Daily Code Talk. Confirm the adopted edition. Distinct from geometry (803.10). This is not a connector specification. Packet: 803.8 PDF · ES.
- 803.8 vent connectors — metal, minimum thicknesses from Daily Code Talk: 0.0136 in. (No. 28 gage) galvanized steel; 0.022 in. (No. 26 B&S gage) copper; 0.020 in. (No. 24 B&S gage) aluminum.
- 803.9(1) low-heat chimney connectors, galvanized steel by diameter: No. 26 gage at 5 in. and smaller; No. 24 above 5 to 10 in.; No. 22 above 10 to 16 in.; No. 16 above 16 in.
- 803.9(2) medium- and high-heat chimney connectors, heavier sheet steel: No. 16 gage up to 14 in. equivalent diameter; No. 14 at 15–16 in.; No. 12 at 17–18 in.; No. 10 above 18 in.
On the set: appliance heat classification, connector diameter, and metal thickness together, citing 803.8, Table 803.9(1), or Table 803.9(2). Do not apply vent-connector minimums to a higher-temperature chimney connector.
Galvanized steel, no gage, medium-heat appliance
The diameter matches the outlet. The installed material can still be two or more gage steps too thin against Table 803.9(2). Too-thin material deforms, burns through, corrodes, and fails at the joints.
Source: Daily Code Talk — IMC 803.8–803.9 · geometry: 803.10 · dampers: 803.5–803.7 · medium-heat: 805.6.
What to send
Appliance heat classification (low / medium / high), connector diameter, and any gage shown on the schedule or spec.
If the schedule says “galvanized” with no gage
Send the appliance type and the diameter. MasterBuild will say which table row applies — before the shop buys the thin roll.
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. Gage and thickness figures are 2024 IMC 803.8–803.9 education from Daily Code Talk — not a connector specification. This page is not legal advice.