All Things Gypsum: Penetrating Fire-Rated Gypsum Board Ceiling Systems
When the installation is evaluated, appearance of the finished interface between the penetrating item and the ceiling membrane, not the function of the ceiling system, is usually the determining factor.
Once you add the element of a fire-rating to the situation, the scenario changes significantly, because once you penetrate the membrane of a fire-rated ceiling (or the ceiling system if it does not have a membrane, for that matter), you bring into play a host of code requirements.
Penetrations in gypsum board fire-rated ceilings (and let’s stay with ceilings in this column to keep it simple; many of the same requirements apply to walls also) typically are of two types: items that penetrate the entire system, such as a pipe or duct; or items that penetrate only the membrane of the system: again a pipe or duct, but also possibly an access door or length of electrical conduit.
Requirements for the proper installation of the penetrating items are contained in Chapter 7 of the International Building Code; however, even with the code language one common question often arises: “How do I penetrate a rated ceiling if the system being penetrated did not contain the penetrating item when it was fire-tested?”
In other words, “You’ve said loud and long not to modify a rated system from the way it was tested. I look in your Fire Resistance Design Manual (FRDM) and I don’t see any systems with penetrations. What do I do now?”
The Simple Answer
The fire test on the ceiling establishes the rating for the system. If that system is to be penetrated or compromised, the modification has to be accomplished in accordance with the procedure outlined in the code. Construct and install the gypsum system in accordance with the design contained in the FRDM. In addition, install the penetrating items based on the listing or test that is being referenced, noting that the source for the fire test information will be a document other than the FRDM.
Code language and penetration element testing have evolved to the point where the individual penetrating item is required to pass a specific fire test before it can be installed in a rated system. For example, an access door that is installed in a rated ceiling must, according to Section 711 of the IBC, be “tested in accordance with ASTM E 119 [for] horizontal assemblies and labeled by an approved agency for such purpose.”
Section 711 on Horizontal Assemblies doesn’t indicate the specific rating that the ceiling system has to maintain. That information is found in other sections of the code. But it does establish that the rating of the system shall “not be less than that required by the building type of construction.” It therefore follows that if the horizontal system has to provide a specific hourly rating, then the access door has to provide, at a minimum, the same rating also; however, it does not require that the exact, specific ceiling system and the precisely designated access door have to be tested together.
In other words, if the ceiling system provides a one-hour rating, then the access door has to have passed an E119 (or equivalent) test where it also achieved at least a one-hour rating. The code does not require the specific access door in question to have been tested with the exact ceiling system being installed; however, it does require the access door to have been tested for use for the purpose intended.
Listings and labels describe the systems in which an access door can be installed and the basic requirements of the system. With a gypsum board ceiling, the listing might describe the type, thickness, and number of layers of board required; the spacing of the framing members; and the method of fastening the door to the system.
Pipes and ducts that penetrate a ceiling and fire-resistant joint systems between ceilings and other rated systems have similar requirements. In the instance of a pipe that penetrates a ceiling, the specific listing might be limited in use to a specific series or type of ceiling system-it might be limited to use with only wood joist systems covered with structural wood panel subflooring, for example-but it is a pretty rare occurrence when a system would be tested with and limited to use with only one specific floor-ceiling system.
Again, the listing for the penetrating item will describe the construction that is appropriate for use with the penetrating item and it may do it in broad terms. As an example, systems described in the Underwriters Laboratories Fire Resistance Directory often refer to a series of similar designs with which the penetrating element may be used. This makes complete sense, for you would not install a 4-inch diameter pipe in both a wood joist and a steel joist system and expect to get the same result. You would however, expect to get the same result from the same diameter pipe when it was repeatedly installed in a series of comparable wood joist systems.
The IBC requires items that penetrate ceiling systems to be tested in accordance with ASTM E 814 or UL 1479 as modified by the code. Similar language is contained in the code for duct penetrations and fire-resistant joint systems.
Given the countless penetrating items that exist and the potential unlimited combination of items and systems that might occur, it stands to reason that requiring each penetrating item to be fire tested with each specific system would be a boon to no one other than a testing lab. It would lead to a situation where the number of building construction methods would be severely limited or the cost to construct a building would increase significantly due to testing requirements. Neither outcome would serve the public interest very well. W&C