Apprentice answer

At what duct size or weight does the code require lateral and longitudinal seismic bracing

3rd YearSeismic Bracing & Vibration ControlStop / Verify

Per international building codes (SMACNA Seismic Restraint Manual), seismic bracing is generally triggered for all commercial projects in high-activity zones if the duct cross-sectional area reaches 6 square feet or larger (36 inx24 in or equivalent), or if the total suspended weight of the system components exceeds 10 pounds per linear foot.

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Plain-English answer

Field checklist

Stop and verify the approved detail, manufacturer instructions, foreman direction, and project specs before touching it.
Per international building codes (SMACNA Seismic Restraint Manual), seismic bracing is generally triggered for all commercial projects in high-activity zones if the duct...

Ask Foreman

Hey boss, I’m on sealing & insulation and need verification before I touch this: At what duct size or weight does the code require lateral and longitudinal seismic bracing? Do you want me to stop here and check the approved detail, submittal, or inspector/manufacturer requirement first?

Verify before acting

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.

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