Replacing Wired Glass in a 45-Minute Corridor
A hospital renovation includes a 45-minute fire-rated corridor. The existing corridor doors have 300 mm × 900 mm vision panels glazed with 6 mm wired glass in steel frames. The owner's consultant wants to replace the wired glass with 6 mm fully tempered glass because staff have complained about the appearance and because tempered glass is marked as safety glazing. The corridor also has two 300 mm × 2100 mm sidelights beside the doors, currently wired glass. The door frames are labeled 45-minute assemblies; the sidelight frames are steel and labeled. The glazing subcontractor is asked to supply and install the replacement glass within the existing stops and beads, which provide 20 mm edge cover. The project specification requires compliance with the local building code and NFPA 80.
1. Can 6 mm fully tempered glass be used in the 45-minute door vision panels and sidelights? Explain.
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No. Fully tempered glass is a safety glazing, but it is not a fire-rated glazing. In a fire, tempered glass can shatter from thermal shock and radiant heat, so it does not maintain the integrity of a 45-minute rated assembly. The existing wired glass may have a fire rating, but traditional wired glass is often not impact-safety glazing. Replacing it with tempered glass solves the impact concern but removes the fire resistance. The correct product must be labeled for both the required fire rating and, where the code requires it, impact safety. Products such as fire-rated ceramic glass or specially listed wired glass may be acceptable if they carry the correct label and are installed within their listed size and framing limitations. The vision panel and sidelight sizes, the steel frame, and the 20 mm edge cover must all fall within the glazing manufacturer's listing. The consultant's proposed substitution should be rejected unless a listed 45-minute glazing is selected.
2. What documentation and labeling should be verified before installation?
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Before installation, the glazier should verify:
- The glazing product carries a permanent label identifying the manufacturer, the fire rating, and any impact-safety rating. The label must be visible after installation or documented in a way accepted by the authority having jurisdiction.
- The manufacturer's listings show that the specific glass type and thickness are permitted in a 45-minute door vision panel and in the sidelight size being used. Fire-rated glazing often has maximum exposed area limits.
- The door and sidelight frames are labeled 45-minute assemblies and are compatible with the glazing. The existing stops and beads must provide the required edge cover and glazing clearances.
- NFPA 80 requires labeled glazing in labeled fire-door assemblies; field cutting, drilling, or substitution of unlisted glass is not permitted.
The submittal should include the product data, listing, and installation instructions. If the label is missing or the product cannot be traced, the glazing should not be installed.
3. If a fire-rated ceramic glass is selected, what installation details matter?
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Ceramic fire-rated glass is not ordinary glass and should be installed exactly as listed. Key details include:
- Edge clearance and glazing tape: The glass must not be pinched or set directly against steel. Use the manufacturer's specified glazing tape or gasket and maintain the required clearance for expansion.
- Stops and beads: The existing stops may need modification to achieve the listed bite and clearance. Do not assume that a 20 mm edge cover is acceptable just because the old wired glass fit; check the listing.
- Fasteners and framing: The frame must be sound, labeled, and compatible with the glazing. Loose or corroded stops can compromise the assembly.
- Labeling: The glass must remain labeled and traceable to the listing. Do not cut or alter the glass in the field.
- Door operation: The added weight or thickness may affect door closers, hinges, and clearance. Verify that the door still operates and latches correctly after glazing.
If the existing frame cannot accommodate the listed glazing, the correct solution is to modify or replace the frame, not to force the glass into an unlisted condition.