603.4 Metallic ducts.
MC § 603.4
Metallic ducts shall be constructed as specified in the SMACNA/ANSI HVAC Duct Construction Standards – Metal and Flexible. Exception: Ducts installed within single dwelling units shall have a minimum thickness as specified in Table 603.4. Table 603.4Duct Construction Minimum Sheet Metal Thickness for Single Dwelling Units a Round Duct Diameter(inches)Static Pressure1/2-inch water gageThickness (inches)1-inch water gageThickness (inches)GalvanizedAluminumGalvanizedAluminum< 120.0130.0180.0130.01812 to140.0130.0180.0160.02315 to 170.0160.0230.0190.027180.0160.0230.0240.03419 to 200.0190.0270.0240.034Rectangular Duct Dimension(inches)Static Pressure1/2-inch water gageThickness (inches)1-inch water gageThickness (inches)GalvanizedAluminumGalvanizedAluminum≤ 80.0130.0180.0130.0189 to100.0130.0180.0160.02311 to 120.0160.0230.0190.02713 to160.0190.0270.0190.02717 to 180.0190.0270.0240.03419 to 200.0240.0340.0240.034 For SI: 1 inch = 25.4 mm, 1-inch water gage = 249 Pa. a. Ductwork that exceeds 20 inches by dimension or exceeds a pressure of 1-inch water gage shall be constructed in accordance with SMACNA/ANSI HVAC Duct Construction Standards – Metal and Flexible.
