This standard specifies the material, construction, and installation requirements for metal air-handling ducts. HVAC and MEP engineers use it daily to determine standard duct sheet thicknesses based on duct dimensions, specify jointing types, and calculate support spacing to ensure structural integrity and prevent noise.
Provides guidelines for the design, installation, testing, and maintenance of mechanical ventilation and air conditioning systems in buildings.
Quick Reference Values
Max side length for 0.63mm (24G) GI sheet750 mm
Max side length for 0.80mm (22G) GI sheet1500 mm
Max side length for 1.00mm (20G) GI sheet2250 mm
Max side length for 1.25mm (18G) GI sheetAbove 2250 mm
Max spacing for duct hangers/supports2.5 m
Min unbraced dimension requiring cross-breaking300 mm
Practical Notes
Always ensure that ducts with larger flat surfaces are cross-broken or beaded to avoid 'oil-canning' (drumming noise) due to internal air pressure variations.
Cross-check the sheet gauge specified in BOQs directly against Table 1 to ensure contractors are not using thinner sheets for large duct widths.
Ensure the raw GI sheets conform to IS 277 and specify the correct zinc coating class based on the project's humidity and environmental exposure.