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We use a significant amount of space in this column to hammer home the axiom that fire-rated systems must be constructed in accordance with an appropriate fire test. In so doing, we have conveniently ignored discussing a handful of related applications where gypsum board is being installed, but no fire test is available. The lack of a fire test in these specific instances typically occurs because the gypsum is not being incorporated into a fire-rated system but is being used to provide a certain measure of fire protection. Specific examples occur throughout the model building codes.

A primary example is in the International Residential Code, where a protective layer of gypsum board is required between habitable space and an attached garage. Section R309.2 of the 2006 IRC requires an attached garage to be separated from the residence by “not less than 1/2-inch gypsum board or its equivalent applied to the garage side.” This requirement applies to habitable space located adjacent to the garage and to any unoccupied attic space above the garage. If the space above the garage is habitable, the code requires 5/8-inch Type X gypsum board to be installed on the underside of the garage lid in lieu of 1/2-inch board.

PASS ASTM 119

Unfortunately, the code creates a bit of a void since it does not specifically address the requirements for applying and fastening the board. This likely stems from the way the language was placed into the IRC. While the concept was a part of the 1995 “CABO One and Two Family Dwelling Code”—the predecessor to the IRC—it was never well explained in the code or in the CABO Commentary. When the relevant CABO language was used as the basis for the IRC, it was grafted into the new code without modification. It remains essentially the same to this day.

Because the 2006 IRC Commentary also provides no answers, one is left with an information hole. In that circumstance, the best relief is found in other sections of the code. In this specific instance, the answer is in Chapter 7 of the IRC.

Section R702.3.5. of the 2006 edition of the IRC establishes the general criteria for applying gypsum board to walls and ceilings when it makes reference to Table R702.3.5. of the code. The table, in turn, defines the correct spacing of fasteners and framing members and the proper size and type of fasteners to be used for an application of gypsum board to either wall or ceiling framing members. Because no other criteria exist, it is this table that should be used to guide the applicator when gypsum board is being installed as required by Section R309.2.

While it seems a bit odd to be using the same application requirements for both a common interior wall and a garage wall that is serving as a protective element in a residence, it must be noted that the garage wall is not a part of a fire-resistive assembly. In describing the required garage wall or lid protection, the code makes no reference to a fire test or a fire rating, it simply instructs the applicator to apply a layer of a specific type of gypsum board. The gypsum board has fire resistive attributes, so a measure of protection beyond that created when no surfacing material is applied to the interior of the garage is achieved, but the wall or ceiling is not required to achieve a specific fire resistance rating.

To illustrate the point further, contrast the garage wall and ceiling situation with the specific fire rating required by Section 317 of the IRC. Section 317 defines dwelling unit separation requirements and contains language that specifically establishes required fire ratings for the walls that divide duplex and townhouse dwellings. The wall between duplex units, for example, must have a one-hour rating. The code does not prescribe the construction that is used to obtain the one-hour rating; instead, it requires the system that is used to pass an ASTM E119 test. Any system tested in accordance with E119 and providing the hourly rating mandated can be used as long as it is installed to match the materials and methods used in the tested system described.

THREE SOURCES

Similar to the garage scenario is the situation encountered when a thermal barrier is required by Section 2603.4 of the IBC. Code language in this instance requires 1/2-inch gypsum board to be applied so that it will “… limit the average temperature rise of the unexposed surface to not more than 250oF after 15 minutes of fire exposure …” Like the garage situation, the code permits the use of gypsum board, but does not prescribe application requirements.

In this instance, the most simple application answer is found outside of the code, in a document created by a code-related organization. To determine the benchmark threshold application requirement necessary to comply with the code, reference the applicable language in Section 4.8 of ICC-ES Evaluation Report ESR-1338. For wood framing, the report deems the application of gypsum board in accordance with ASTM C840 or IRC Section R702.3.5. to be acceptable. For other framing types, one must consult an appropriate evaluation report. Because thermal barrier applications generally incorporate foam plastic insulation or similar materials, the evaluation reports for those materials and systems generally contain specific thermal barrier instructions.

In other areas, the code permits the use of gypsum board as a type of fire-resistive element; however, the code never fully establishes the application requirements for the gypsum board, and it also does not contain any similar application scenario that can be used as a template. A specific example is when the IBC permits gypsum board to be used as an alternative to a parapet—most prominently described in Chapter 7—but the requirements for attachment of the gypsum board are not specifically defined.

In this case, the best relief is afforded by a document exterior to the code that has been created by the Gypsum Association to specifically address the situation: GA-276, Gypsum Board Roof Underlayment Systems. Because the application of the board in this instance is not highly technical—you’re essentially laying board on roof rafters where the roofing system will hold it in place—the requirements are reasonably minimal. The document provides elementary size and spacing information for the few fasteners that are needed to hold the board in place.

Three different application challenges inspire three different resolutions: one that found its answer within the code; the second which required the use of a document created by a code-related entity; and the third which required the use of a document created by an industry organization. In all three instances, the answer was available but not obvious. Sometimes it takes a bit of searching.

Again, if it is a fire-rated system, the gypsum board should be installed in accordance with the test report. In those few instances in the codes where gypsum board is used to provide some measure of fire protection outside of an application that references a fire test, resolution of application issues may need to be obtained through the use of other code sections or outside documentation. W&C