Firestopping a Rated Corridor Penetration
Your crew is pulling 60 Cat 6 cables through a 100 mm (4 in) sleeve in a 2-hour rated corridor wall. The sleeve was installed by the masonry contractor and is not listed as part of any firestop system. The cables are a mix of CMP and CMR; the corridor is a return-air plenum. The general contractor's schedule has the ceiling closing in 48 hours. The fire marshal has already walked the site once and noted the open penetration. Your foreman wants to 'stuff it with mineral wool and caulk it' and move on. The electrical subcontractor has a leftover intumescent sealant on site that is listed for plastic pipe, not cable.
1. Evaluate the proposed firestop approach and state what is actually required.
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The proposed approach is non-compliant. Firestopping must use a listed system (e.g., an ASTM E814/UL 1479 tested system) for the specific penetration: the wall type, the sleeve, the cable types and quantities, and the annular space. 'Mineral wool and caulk' is not a system unless it matches a listed detail exactly.
The leftover intumescent sealant listed for plastic pipe is not acceptable for a cable bundle - the listing is for a different substrate and the test data does not cover cables.
Required:
- Select a listed firestop system from the manufacturer's catalog that covers a 100 mm sleeve in a 2-hour rated wall with the actual cable count and mix (CMP/CMR), and the annular space.
- Use the specified materials, thickness, and installation method exactly as tested (including any required backing, dam, or sleeve treatment).
- Install per the manufacturer's instructions and the listed detail.
- Document with photos and the system number on the as-built.
- Because the corridor is a return-air plenum, the firestop must also maintain the smoke seal - the listed system must address smoke leakage, not just flame.
Do not let the 48-hour schedule drive a non-compliant install. Escalate to the GC and fire marshal if the correct materials are not on site.
2. The sleeve is not part of a listed system. What are your options?
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Options in order of preference:
- Remove/replace the sleeve with a listed sleeve or eliminate it and treat the wall opening directly with a listed system for a cable penetration in the wall assembly. This is cleanest if schedule allows.
- Use a listed system that accommodates an unlisted sleeve - many manufacturers publish systems for cables through a metallic or non-metallic sleeve; verify the sleeve material, diameter, and wall type match the listing. If the masonry sleeve is concrete/block, confirm the listed system covers that substrate.
- Ream/enlarge or line the sleeve if the annular space is too tight for the required sealant depth; the listed system specifies min/max annular space.
If none of these can be met within the schedule, the correct answer is to stop and issue an RFI - not to improvise. The fire marshal has already flagged it, so a non-compliant patch will be caught and cost more to redo.
3. What documentation and inspection steps close this out?
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- Firestop submittal: manufacturer's listed system cut sheets and installation instructions, submitted and approved before install.
- Installer qualification: many jurisdictions and specs require firestop installers to be trained/certified by the manufacturer; confirm your crew's credentials.
- Inspection: the AHJ/fire marshal inspects the penetration; schedule the inspection before the ceiling closes. The 48-hour ceiling deadline must yield to the inspection.
- Photos and log: photograph the penetration before and after, record the system number, cable count, date, and installer on a firestop log.
- As-built: mark the penetration and system on the life-safety/as-built drawings.
- Plenum smoke seal: confirm the system maintains the smoke seal for the return-air plenum and note it in the documentation.