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Ductwork - Supports

Recommended distance between ductwork support hangers.

The support distance for ductwork is typical based upon deflection, stress and cylinder buckling analysis.

duct supports

For sheet metal duct work the space between the hangers should not exceed the distances listed below:

Horizontal Ductwork

Ductwork - Support Spacing
Ducts SizeMaximum Spacing
(ft, m)
(ft2, m2)
(in, mm)
less than 4 (0.4) less than 5 (125) 8 (2.5)
(0.4) to 10 (1) 5 (125) to 38 (1000) 6 (2)
more than 10 (1) more than 38 (1000) 4 (1.2)

Vertical Ductwork

Ductwork - Support Spacing
Ducts TypeMaximum Spacing
(ft, m)
round 12 (3.6)
rectangular 10 (3)
  • 1 ft2 = 0.0929 m2 = 144 in2
  • 1 ft (foot) = 0.3048 m = 12 in

Note! Support systems for ductwork may provide restraint in three directions against displacement and rotation. Consideration must be given with restraining ducts to avoid development of excessive internal duct stresses caused by expansion or contraction due to temperature variations.

Related Topics

  • Ventilation Systems

    Design of systems for ventilation and air handling - air change rates, ducts and pressure drops, charts and diagrams and more.

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