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§ 18-28-603.3 — Metallic ducts

Municipal Code of Chicago (2026 S-74, current through Council Journal of June 17, 2026) · Municipal Code of Chicago § 18-28-603.3

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18-28-603.3 Metallic ducts.

All ducts shall be constructed of iron, steel, aluminum or other approved material. Ducts shall be constructed as specified in the SMACNA HVAC Duct Construction Standards – Metal and Flexible. Exception: Ducts installed within single dwelling units shall have a minimum thickness as specified in Table 18-28-603.3. Table 18-28-603.3 Duct Construction: Minimum Sheetmetal Thicknesses for Single Dwelling Units Duct Size | Galvanized Steel | Approximate Aluminum B&S Gauge Minimum thickness (inches) | Equivalent galvanized Gauge No. Duct Size | Galvanized Steel | Approximate Aluminum B&S Gauge Minimum thickness (inches) | Equivalent galvanized Gauge No. Round ducts and enclosed rectangular ducts | | | 14" or less | 0.013 | 30 | 26 Over 14" | 0.016 | 28 | 24 Exposed rectangular ducts | | | 14" or less | 0.016 | 28 | 24 Over 14" | 0.019 | 26 | 22 For SI: 1 inch = 25.4 mm