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Apprentice answer

Can you hang heavy duct from the bottom chord of an open-web steel joist

3rd YearHangers, Supports & AnchorsStop and get direction

Do not put heavy point loads on a joist chord without approved structural direction. Hold the load and move to an approved distributed support detail.

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Plain-English answer

Open-web joists are not generic hanger racks. A heavy exhaust plenum or large duct can twist a bottom chord if the load is placed wrong.

Stop adding weight, support the duct safely, and get the foreman/GC/engineer involved. Likely recovery is a structural bridge across multiple joists, panel-point attachment, beam clamp layout, or engineered hanger frame.

Ask Foreman

This heavy duct/plenum is being carried by the open-web joist bottom chord at [location]. I see the steel twisting. Do you want us to hold and get an approved bridge/panel-point support detail?

Verify before acting

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

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