This "fluid personality" of a model code is beneficial in that it allows the code modification process to take a very adaptive attitude toward new technologies in materials and installation methods. It also helps keep references to the standards that are incorporated in the code up-to-date and relevant. However, the personality also has an unfortunate "dark side": an alter ego that occasionally causes problems for both code officials and contractors.

The primary negative aspect of the fluid nature of a code is its tendency to facilitate incorrect or uninformed interpretation. By its very character, a model code is subject to interpretation-put enough words down on enough pieces of paper and no two individuals are going to read them the same way-but because a code's content is revised every few years, the consequences of faulty analysis can be compounded when the effect of an interpretation that was once slightly incorrect becomes substantially wrong over time.

Reader's digest

So who helps when a code interpretation is required? One excellent source of relief is an evaluation report, such as those produced by ICC Evaluation Services Inc., a division of the International Code Council.

ICC-ES is a nonprofit, public-benefit corporation that performs technical evaluations of building products, components, methods, and materials. It came into being in February 2003, when America's four building-product evaluation services officially combined their operations. The four "legacy" evaluation services that came together to form ICC-ES were the National Evaluation Service Inc.; BOCAI Evaluation Services; ICBO Evaluation Service Inc.; and SBCCI Public Service Testing and Evaluation Services Inc. Through the legacy evaluation services, ICC-ES has a history that goes back more than seventy years.

An ER essentially summarizes the findings of ICC-ES as to the compliance with code requirements of the subject of the particular report-a particular building product, component, method, or material. The reports are issued with a specific life, typically one but occasionally two years and are available for free from a variety of sources. While ICC-ES does charge a fee to the organization that requests the report, the actual report itself can be obtained at no cost by any individual.

Where an ER is helpful is that the information is generally viewed as being legitimate and enforceable by a code official. A code authority can review the report and can operate with the confidence that the material contained therein has been scrutinized by a code-related organization and that the items described in the report will comply with a code-approved application.

The Gypsum Association has sponsored evaluation reports for many years, initially with ICBO Evaluation Services and now with ICC-ES. For many years, the association sponsored two reports: one that addressed common installation situations for gypsum board and a second that primarily contained fire- and sound-test information. Approximately two years ago, the association decided to combine the two reports into one document-there was a considerable amount of redundant information that was written into both reports-and in September 2005, ICC-ES issued the new version of ESR-1338 that contained relevant information from both predecessor reports.

ESR-1338 is chock full of nuggets of information that can help any contractor when confronted with specific situations that might require code interpretation.

Straight to the point

Tagging onto that concept is Section 4.2.1.c. that states, "(e)xcept where otherwise noted in this report, any of the gypsum boards listed in Section 3.0 of the same size, thickness and core type specified, may be used." This provision is the statement that allows an applicator to use, for example, water-resistant gypsum board in a system contained in GA-600 that only incorporates gypsum wallboard in the fire test description. This clause also is applicable to the other tested systems described in ESR-1338, many of which are unique to the report and are not described in other resources.

ESR-1338 also confirms the language in Chapter 25 of the IBC regarding instances where joint treatment may be eliminated in a fire-resistance-rated system. A little-known code provision exempts joints and fasteners in a multiple-layer system from finishing requirements when the joints of adjacent layers of gypsum board are offset from each other. Section 4.2.3.3 of ESR-1338 confirms this provision and elaborates it for clarity.

Section 4.2.3.2 contains language that allows an applicator to substitute screws for nails in fire-resistance-rated systems provided, "the screw penetration into the framing member is equivalent to the nail penetration, the screw spacing is the same as the nail spacing, and the cross-sectional area of the screws is equal to that of the specified nails." This statement, while a basic principle of fire-resistive construction, does not appear anywhere in the IBC or the IRC. Rather, it is contained in both GA-600 and the Fire Resistance Directory, published by Underwriters Laboratories Inc. Not having it directly in the code can occasionally cause a headache; having the information in ESR-1338 provides interpretive relief.

Myriad other circumstances, such as the use of gypsum board as a thermal barrier, as a component of a shear wall or ceiling diaphragm system, as a tile backing material, as a building exterior substrate, or as an underlayment component of a special cedar shake or shingle roof assembly are also addressed by ESR-1338.

So, whether a contractor, material supplier, architect or just wanting to become better educated on the use of gypsum board, a copy of ESR-1338 should be obtained. It is available from the association's Web site www.gypsum.org. Copies of available evaluation reports on a variety of subjects may be obtained from the ICC-ES Web site at www.icc-es.org.