Static field route #19064

What do I do when the Unistrut trapeze is bowing under a heavy duct run?

Hanger Systems, Rods, Straps, Trapeze & Anchors🟨 CHECK FIRSTV190 answer-gap expansion

📖 Verified core answer

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.

Open in Field Rescue Open category

Field verification checklist

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.

Ask foreman

The trapeze under this [duct size/type] is bowing at [location]. I checked the span and added load. Do you want heavier strut, another rod/support point, closer spacing, or an engineered support detail?

Text to foreman

Route options

AMake the field correction only if it is within your assignment and the approved method.

BHold and document the condition if the fix affects airflow, access, life safety, pressure class, rated assemblies, equipment, or another trade.

CBring the foreman/detailer the location, what you checked, and what decision you need before cover, startup, or rework.

Do not do this

Do not ignore a sagging trapeze or try to hide the bow by raising one side of the rods.

Why this matters

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

Verification basis

Approved drawings/specs, project coordination drawings, manufacturer instructions/submittals, shop standards, foreman/detailer direction, employer policy, and AHJ/code requirements.