603.3 Metal Ducts — 2025 California Mechanical Code
California Mechanical Code (Title 24, Part 4) · 2025 edition · updated 2026-09-25 · California
CBSC: official editions, supplements and errata
Italicized text is a California amendment to the model code, as printed in the official publication.
Cite as: 2025 California Mechanical Code (Title 24, Part 4) § 603.3 · Effective January 1, 2026 · Official source: Building Standards Commission
Ducts shall be supported at each change of direction and in accordance with SMACNA HVAC Duct
Construction Standards – Metal and Flexible. Riser ducts shall be held in place by means of metal straps or angles and channels to secure the riser to the structure.
Ducts shall be installed in a building with clearances that will retain the full thickness of fireproofing on structural members.
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