All Things Gypsum
Work to Code With Gypsum Board
The answer to the last question is pretty straightforward. Building to code in modern society helps to ensure a level of consistent quality in construction that provides citizens with structures that are safe to occupy and that do not detrimentally impact adjacent buildings. While zoning laws probably do as much, if not more, than building codes do to keep buildings that might adversely impact each other from being located in close proximity-to cite a ridiculous example, think of the adverse impact of having a dynamite factory adjacent to an elementary school-building codes make sure that both the elementary school and the dynamite factory are constructed using proper structural, fire safety and engineering concepts; that they provide safe egress in the event of a fire; and that they allow for adequate access for emergency personnel in the event of an accident.
In the absence of building codes, residential and commercial building construction would essentially be lawless and structures would be built based only on good faith. A scary situation if there ever was one.
Experience levelSo, whether you have decades of experience or no experience whatsoever, you are bound-generally by law-to "build it to code."
Consensus model building codes have been in use in the U.S. since the first half of the 20th Century. And they have generally incorporated language about gypsum board since their inception.
Today, most of the U.S. has adopted or is in the process of adopting, the International Building Code for use in non-residential construction and the International Residential Code for constructing one- and two-family dwellings. While the predecessor codes to the IBC and the IRC are still being used in some jurisdictions (most notably California where the 1997 Uniform Building Code remains in effect), and a model code-NFPA 5000 Building Code-has been developed by the National Fire Protection Association and is in use in some limited areas, most states and localities have adopted or are in the process of adopting the IBC, the IRC and the other codes published by the International Code Council.
The use of gypsum board is generally regulated in the IBC by the provisions contained in Chapter 25 of the code. That chapter governs "the materials, design, construction and quality of gypsum board, lath, gypsum plaster and cement plaster."
Chapter 25 contains tables that identify the types of gypsum board materials that may be used and the standards to which the gypsum board application must conform to be considered code-compliant. Specifically, gypsum board, other than gypsum sheathing or gypsum veneer base, must be installed in accordance with ASTM C840, Standard Specification for the Application and Finishing of Gypsum Board, or GA-216, Application and Finishing of Gypsum Panel Products, to comply with the code.
Buried in Chapter 25 are provisions that allow for modifications to the referenced standards. For example, Section 2508.4 of the 2003 IBC contains language that exempts specific applications of gypsum board from standard provisions that require all the joints and fasteners in a fire-rated system to be finished with joint treatment. These provisions are fairly unique to the IBC and do not generally appear in other industry or fire testing documents.
In general, code language trumps all other language except for law. Section 102.2 of the code is very specific:
"The provisions of this code shall not be deemed to nullify any provision of local, state or federal law."
The law comes firstIf a law contains a provision that is stricter than the model code, the law-not the code-is enforced first. And this occasionally happens with code enforcement, specifically in sections that contain fire-related provisions. However, if there is a conflict between the code and a document referenced by the code, then the code takes precedence unless the document is a "law." This is clearly stated in Section 102.4, "Where differences occur between provisions of this code and referenced codes and standards, the provisions of this code shall apply."
An excellent example of this concept is the language in Chapter 25 that prohibits an installation of gypsum board until "weather protection for the installation is provided." This language is stricter than that contained in GA-216 or ASTM C840 and essentially prohibits installation of gypsum board in a building that is not weathertight.
Much of the way gypsum board is used in non-residential construction is defined by the provisions contained in Chapter 7 of the IBC. This chapter addresses fire-resistance-rated construction and it defines the "materials and assemblies used for structural fire resistance and fire-resistance-rated construction separation of adjacent spaces to safeguard against the spread of fire and smoke." In essence, it defines how to construct fire-resistance-rated construction systems and the test standards for the systems.
Chapter 7 is the section of the code that identifies gypsum board as a noncombustible building material. Section 703 contains provisions that establish noncombustiblity requirements for composite materials and gypsum board complies with these requirements. As a consequence, gypsum board may be used in any type of code-compliant building construction.
The same chapter also defines construction requirements for firewalls, fire partitions, shaft walls and vertical and horizontal fire barriers. All of these systems are required to comply with different code requirements and all can be constructed using gypsum board systems.
A firewall, for example, has to be continuous from the top of the foundation to a termination point at least 30 inches above the adjacent roof, unless the roof is protected with a code-compliant system. A firewall also must be structurally stable in the event of a fire to allow for collapse of construction on either side of the wall without allowing the wall itself to collapse. In other words, if a fire occurs on one side of the wall and the building on that side collapses, the fire wall must remain intact and not collapse with the structure.
Firewalls never carry less than a 2-hour fire rating and typically are required to be 3- and 4-hour rated systems. A fire partition, on the other hand, simply must provide a 1-hour fire rating. It has no collapse requirement and is not required to penetrate the roof structure. Firewalls are typically used to separate buildings into smaller fire areas or to separate buildings to accommodate different usage. Fire partitions are used to separate dwelling units in the same building or to frame corridor walls.
With the exception of provisions for townhouse separation walls and separating attached garages from adjacent occupied space, the IRC does not contain significant fire-resistant construction language. Unlike the IBC, however, the IRC does not reference standards for the application of gypsum board; instead, it defines the criteria for board application in Chapter 7 of the code primarily through the criteria contained in Table R702.3.5. The IRC does incorporate material reference standards in the same way that the IBC does.
Gypsum board enjoys a respected position in building codes, a position that is not undeserved given its long history of successful incorporation into residential and non-residential construction. Because it is used in a variety of situations throughout the construction process, references to its use appear in a number of different locations in both the IBC and IRC. In future columns, we'll dig into and discuss some of the lesser-known aspects of code-compliant gypsum board use. We'll also discuss the evolving code situation in Canada.