/ Field knowledge · IMC 607.7
Flex does not cross the rated line.
IMC 607.7: flex does not cross a rated assembly. No gage substitution. No “short run” allowance. If the boundary is rated, the flex stops and listed sheet steel with the right 607.5 / 607.6 protection carries through.
Educational 2024 IMC 607.7. Confirm adopted edition and the life-safety plan. This is not a damper selection. Air connectors — the listed flexible connectors at equipment — carry the same restriction. They are a terminal device, not a rated-penetration component.
- Flexible air ducts and air connectors shall not pass through any fire-resistance-rated assembly. That is a prohibition, not a damper option.
- “Any rated assembly” is broad: rated walls, floor/ceiling and roof/ceiling assemblies, rated ceiling membranes, shafts, fire barriers, fire partitions, fire walls, smoke barriers, and smoke partitions.
- The rated line is still crossed by listed sheet steel duct with the damper, sleeve, firestop, or shaft protection 607.5 and 607.6 require for that assembly.
Last three feet through the corridor wall
Follow every flex run back to hard duct. If it crosses a rated wall, shaft, ceiling membrane, or floor, correct it before the boundary is concealed. Overlay the life-safety plan on the M-sheet before anyone cuts flex.
Source: DCT 607.7 · tool: flex screen · dispersion: 603.17 · outlets: 603.18 · dampers: 607 · construction: 603.
What to send
The RCP, the rated-wall plan, and whether any flex is shown through a corridor, shaft, or rated ceiling.
If the flex tails through the corridor
Send the RCP. Masterbuild will say whether 607.7 even allows that run — or the flex has to stop and hard duct take the rated line.
Send Project Background+1 (786) 398-6940 · osmany.portal@masterbuildconsulting.com
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