Gaps in Ceilings

Q: I am looking for the 1/8-inch gap reference for ceiling tiles. If the ceiling has broken tiles, or misaligned tiles, or gaps greater than 1/8-inch caused by anything (such as data cables temporarily run up through the ceiling), then I see that the surveyors will cite this. Is that actually written in the NFPA codes and standards anywhere? Is the 1/8-inch gap rule “real”? Does it use the 1/8-inch measurement anywhere? If so, where? If not, where does it come from?

A: No, there is no direct statement in the LSC that says gaps greater than 1/8-inch are prohibited, but ceilings containing smoke detectors and sprinklers must form a continuous membrane and any sizable gap in this membrane would allow smoke and heat to rise above the ceiling which would delay the activation of the detector or sprinkler, thereby causing an impairment.

Since the size of the gap must be quantifiable, and NFPA does not say how big the gap has to be before it is a problem, authorities having jurisdiction have ‘borrowed’ the 1/8-inch gap concept from NFPA 80 regarding the gap between a fire door and the frame. Authorities having jurisdiction are permitted to do this as section 4.6.1.1 of the 2012 Life Safety Code says the authority shall determine whether the provisions of the LSC are met. This means, when the Life Safety Code is not clear on a subject, the authorities have to make interpretations in order to determine compliance.

Strange Observations – Ceiling Penetrations

Continuing in a series of strange things that I have seen while consulting at hospitals…

This picture was taken in an electrical room. Where the conduits extend upwards and penetrate the suspended ceiling, the gaps around the conduits are too large.

Most surveyors will use the NFPA 80 maximum 1/8-inch gap rule fire door clearance to frames as a standard for the maximum gap around conduit penetrations, where the ceiling is required to act as a membrane for smoke detectors or sprinkler heads.

In situations like this, the easiest and best solution is to remove the suspended ceiling from the electrical room, and relocate the lights in the ceiling to the deck above.