603.7 Support of Ducts — 2025 California Mechanical Code

Ducts shall be supported in accordance with the manufacturer’s installation instructions; and Section 603.7.1, Section 603.7.2 or Section 603.7.3.

603.7.1 Metal Ducts. 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.

603.7.1.1 Rectangular Ducts. Supports for rectangular ducts shall be installed on two opposite sides of each duct and shall be riveted, bolted, or metal screwed to each side of the duct at intervals specified.

603.7.1.2 Horizontal Round Ducts. Horizontal round ducts not more than 40 inches (1016 mm) in diameter where suspended from above shall be supported with one hanger per interval and in accordance with Section 603.7.1.3 through Section 603.7.1.5. 603.7.1.3 Tight-Fitting Around the Perimeter. Ducts shall be equipped with tight-fitting circular bands extending around the entire perimeter of the duct at each specified support interval.

603.7.1.4 Size of Circular Bands. Circular bands shall be not less than 1 inch (25.4 mm) wide nor less than equivalent to the gauge of the duct material it supports.

Exception: Ducts not more than 10 inches (254 mm) in diameter shall be permitted to be supported by No. 18 gauge galvanized steel wire.

603.7.1.5 Connection. Each circular band shall be provided with means of connecting to the suspending support.

603.7.2 Flexible Air Ducts. Flexible air ducts shall be supported in accordance with Section 603.4. 603.7.3 Other Ducts. Other approved ducts shall be supported in accordance with the manufacturer’s installation instructions.