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Apprentice Q&A · #293

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

3rd YearJoists / Structural CoordinationRED · Stop 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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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.

Field checks

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?

Text this

Do not do this

Do not wrap heavy duct straps around random joist chords or web members.

Why this matters

Wrong joist loading can damage the roof/floor structure and trigger serious inspection and safety issues.

Final direction still comes from approved drawings, specs, manufacturer instructions, employer policy, foreman/detailer direction, structural/seismic details, and AHJ/code requirements.