by eyetee | December 2, 2013 8:30 am
By Joseph Berchenko AIA, CSI, CCS
For testing certain wall assemblies, the 2012 International Building Code (IBC) requires National Fire Protection Association (NFPA) 285, Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Non-load-bearing Wall Assemblies Containing Combustible Components. (That standard’s title notwithstanding, the test is performed on both load-bearing and non-load-bearing wall assemblies.) Its successful completion demonstrates the ability of an exterior wall mockup to contain vertical and horizontal flame spread across the face and through the wall’s core.
Increased use of continuous insulation (ci) in building envelopes has meant enforcement of provisions requiring NFPA 285 testing has recently been stepped up, sparking discussion and concern on Internet bulletin boards and in professional journals. Specifiers must learn where and how to specify compliance with the standard. Additionally, designers must take care in matching details of project-specific wall assemblies to tested assemblies.
IBC generally requires exterior walls in Types I, II, III, and IV construction be built of noncombustible materials. Combustible insulation and wall facings are allowed in some cases, but this is tightly regulated and often includes a requirement for NFPA 285 testing.
Perhaps the most far-reaching mandate for NFPA 285 testing occurs in Chapter 26, which regulates plastics such as foam insulation. Testing is required for Section 2603.5.5. (i.e. exterior wall assemblies of Type I, II, III, and IV construction of any height containing foam-plastic insulation). Compliance with 2603.5 is also mandated in some cases by reference from Section 2612, which regulates the exterior use of fiber-reinforced polymer materials.
NFPA 285 testing is also required for Section 1403 (i.e. exterior walls containing combustible water-resistive barriers in Types I, II, III, and IV construction when more than 12.2 m [40 ft] above grade).
Since water-resistive barriers (WRBs) are a common feature of modern construction, this requirement impacts many high-rise buildings.
During the 2012 Code Change Cycle, the National Institute of Building Sciences (NIBS) and the American Institute of Architects (AIA) jointly sought—and were granted—a modification clarifying and providing exceptions to the WRB rule that will appear in the 2015 edition of the IBC. (Attempts to modify Section 2603.5.5 were unsuccessful.) In 2015, IBC Section 1403.5 will include the following exceptions:
Other IBC sections also require NFPA 285 testing of the following individual components and systems:
Finally, IBC Section 718.2.6’s Exception 3 allows fire blocking to be eliminated in concealed spaces behind exterior wall coverings when the wall covering has been tested according to NFPA 285.
NFPA 285 testing
The NFPA 285 test requires a wall assembly mockup spanning two stories with a test room on each floor. A single window opening is provided from the first story where a test burner is located. The burner is used to send a plume of flame through the window opening and up the exterior surface of the wall above. This simulates a fire that begins in an interior space, breeches a window, and spreads upward along the wall face. Such a scenario replicates a situation common in real-world fires.
Two areas of mockups are of special concern:
For walls with cavities containing foam-plastic insulation or combustible WRBs, the protection of the cavity is paramount. In addition to the fire-resistive properties of the materials, successful test completion generally requires the wall cavity be protected by a continuous steel shelf angle and mineral-wool fire safing or other fire-blocking material. The configuration, thickness, and arrangement of fire-blocking materials for each test are detailed in the test report.
In the case of combustible wall facings (e.g. EIFS, MCM, HPL, and foam-insulation-core panels), the materials must be sufficiently fire-resistive in and of themselves to withstand flame exposure for the duration of the test.
Unfortunately, there is no third-party compilation of assembly tests, unlike the thousands of variations of fire-resistive wall assemblies tested and documented in the FM Global Approval Guide, Intertek ETL SEMCO Directory of Listed Products, and Underwriters Laboratories (UL) Fire Resistance Directory. However, numerous proprietary NFPA 285 tests have been performed by manufacturers, and may be accessed on their websites. To ensure compliance for wall assemblies, it is important designers study successful assembly tests and detail project-specific assemblies that exactly match tested assemblies.
For large projects, consideration might be given to creating mockups of significant or unusual wall configurations and requiring preconstruction NFPA 285 laboratory testing. Although this is an expensive proposition, in projects of sufficient size it may help smooth permit review and will assure the owner the design provides adequate safety.
For Types I, II, III, and IV construction, requirements for NFPA 285 fire testing for individual products should be addressed in each section containing combustible exterior wall components. For example, NFPA 285 testing may be required in sections containing foam insulation, sheathing, foam-insulation-core panels, MCM panels, WRBs, and elsewhere as needed.2
It is tempting to simply add a general requirement in the Part 2 “Performance Requirements” Article in each affected section calling for indicated assemblies to be NFPA 285-compliant. However, this is not only open-ended, but also, because it addresses the assembly, may imply the contractor is responsible for, or can alter, the assembly design. The specifier more commonly just wants to convey to the contractor a manufacturer has tested the wall assembly shown on the drawings with various acceptable products—not that the contractor must take full responsibility for the wall’s code compliance.
For example, an insulation manufacturer may advertise an exterior wall assembly that has been successfully tested with a dozen different WRBs. The specifier may wish to instruct the contractor that any of those—but only those—water-restive barriers are acceptable. This author believes the best way to do this is add an NFPA 285 testing requirement in the water-resistive barrier section at that product type. For example:
Fire Propagation Characteristics: Passes NFPA 285 testing as part of an approved assembly.
Compliance of tested components is indicated in manufacturers’ product data sheets, similar to other test compliances. A full copy of test results is not typically required by codes authorities, although the architect may request a copy of product data, tests, or other documentation in the “Informational Submittals” Article in Part 1 of each affected section, if desired.
The contractor, who is assigned responsibility for securing the building permit by the American Institute of Architects (AIA) A201, General Conditions of the Contract for Construction, is responsible for submitting documentation to the code authority; it is not necessary to detail the contractor’s submittals to codes offices in the technical specifications.
Some combustible products and systems may have International Code Council Evaluation Service (ICC-ES) reports in which they are explicitly approved for use in or on exterior walls of buildings of Type I, II, III, and IV construction. Many codes authorities are willing to accept these reports as evidence of compliance.
Although the construction community must undergo a learning curve for NFPA 285 testing, protection of the health, safety, and welfare of building users remains the highest professional obligation. Strict code compliance is part and parcel of this obligation. Increased understanding and compliance with NFPA 285 code provisions will ultimately create better, safer buildings.
1 Although NFPA 285 is not specifically invoked by name, these systems are required to meet the performance characteristics required in ASTM E2568, Standard Specification for PB Exterior Insulation and Finish Systems. In its Table 3, this standard, in turn, mandates NFPA 285 compliance.
2 In the case of EIFS, requiring compliance with ASTM E2568 is adequate.
Joseph Berchenko AIA, CSI, CCS, is the assistant director of architectural specifications for ARCOM MasterSpec, where he supervises the maintenance and updating of more than 400 architectural/structural/engineering for the master guide specification system. A licensed architect with 35 of years of experience in the construction industry, Berchenko served as a commercial plans examiner for Lincoln, Nebraska’s Department of Building and Safety before becoming a specification writer. He is a past-president of CSI’s DC Metropolitan Chapter. He can be contacted at firstname.lastname@example.org.
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