Why is my duct trapeze bowing and how should it be corrected?

A bowed trapeze means the support is overloaded, undersized, or spanning too far. Do not leave the duct hanging on a deflected support; verify the load and upgrade the support method.

['If a trapeze bar bows under a large duct, the duct may be physically up but the support detail is telling you it is wrong. Big double-wall duct, heavy gauge duct, lined duct, outdoor duct, or extra added loads can exceed a light support setup.', 'The recovery is to support the load correctly: stronger strut/channel, closer hanger spacing, additional rods, a center support, or an engineered support detail. The exact rod/channel/anchor choice should follow the approved support schedule and foreman/detailer direction.']

Stop if

• Use this as training guidance. The foreman, approved drawings, project specs, manufacturer installation instructions, employer safety policy, and AHJ/code requirements always control the final answer.

Check

• A deflected support can lead to sagging duct, joint stress, vibration, failed inspection, or hanger failure.

Steps

• Measure the duct size, span between rods, and where the strut is bowing.
• Check whether the duct is double-wall, lined, heavy gauge, wet/outdoor, or carrying extra load from another trade.
• Look for rods pulling out of plumb, anchors moving, insulation crushed, or joints dipping.
• Compare the support setup against the approved hanger/support detail.
• Temporarily support or unload the condition if there is a risk of failure.

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