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Apprentice Q&A · #295

Can you hang duct from a diagonal web rod in an open-web steel joist?

3rd YearJoists / Structural CoordinationRED · Stop and get direction

Do not hang a duct trapeze from a diagonal joist web member unless the structural detail specifically allows it. Move the load to an approved support point.

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Answer

Diagonal web members are part of the joist structure, not general hanger points. Side-loading one can bend the member and damage the joist.

Support the duct, remove the wrong attachment, and move to approved chord/panel-point support or an engineered bridging member.

Field checks

Ask foreman

The trapeze at [location] is clamped to a diagonal open-web joist member and it is bowing. Do you want us to shift to an approved chord/panel point or engineered bridge?

Text this

Do not do this

Do not side-load joist web rods because they are nearby and convenient.

Why this matters

Wrong structural loading can bend joists, fail inspection, and create overhead support failure risk.

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