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Fire & Life Safety Section: Assessing and Addressing the Dangers of Modular Home Construction
IAFC On Scene: June 1, 2010 “Know your battleground.” That’s the advice passed on from senior officers to those coming up the ladder behind them. In a very unpredictable business, knowing as much as possible about the buildings and situations we may confront prepares us to enter, work and get out safely. Every so often, a situation presents itself that causes us to reconsider what we think we know and modify our response in both tactics and policy. Such is the case of fires in manufactured (modular) buildings. Two house fires in Massachusetts in 2008 have focused attention on two construction techniques unique to modular construction: the creation of large void spaces between levels of multistory buildings and the use of polyurethane foam structural adhesives to affix gypsum board in ceiling and partition wall assemblies. In fact, it’s been learned that many modular-home manufacturers use foam adhesives as an alternative to mechanical fasteners. The ceilings we assume are held in place by screws may simply be held in place by glue that researchers tell us ignites fast, burns completely and loses most of its mass. In addition, the same researchers tell us that the foam adhesive decomposes—it changes from a solid to a gaseous state and emits a flammable vapor—at 250 degrees Celsius! What temperatures can we expect at the ceiling level in a room and contents fire? A look at model and state building codes reveals a prescriptive schedule detailing the use of mechanical fasteners with and without the use of adhesives. A fire chief or building official seeking guidance would walk away from that code review and believe that ceilings and partition walls affixed with adhesives are required by code to include some sort of mechanical fastening. However, as we continue to learn, nothing is as simple as it looks! The same model and state codes allow for the use of “alternative design and construction methods.” This administrative clause results in approval being granted for alternative methods from those prescribed in the code when certain performance standards are achieved. A further review of the codes reveals that the adhesives themselves are required to meet certain ASTM performance standards. These standards fail to address the performance of the foam adhesive under the stresses caused by fire or high heat conditions. In short, approval has been granted for glue to be used as an alternative to screws when there appears to be no data available to determine at what temperature we can expect a ceiling to fail. A ceiling held up only by highly flammable glue. A ceiling that serves as the lower membrane of a void space that often runs 48’ by 14’ by 20 inches high. In other words, how soon can we expect a room-and-contents fire to become a structure fire involving a large void space that spans the length of the building? Armed with this information and these questions, the Fire Chiefs Association of Massachusetts petitioned our state code developers for change. In April, a new section of the Massachusetts Building Code that requires mechanical fasteners in the ceiling assemblies of all buildings was approved. In essence, the state revoked the “alternative design” authorization and now requires compliance with the prescriptive schedule of fasteners already found in the code. It’s important to note that representatives from the modular industry confirmed the absence of data that demonstrates the performance of the foam adhesives under fire conditions. The industry has pledged to conduct independent research and report their findings back to the state before the October 13 enactment date of the new code section. Unfortunately, the code developers tabled our request to make the overall size of the void space smaller by means of draft-stopping. The presence of polyurethane foam structural adhesives is unique to manufactured building construction. This glue forms a bond between the back paper of the gypsum board and the side of the wood framing member. Research available on the effectiveness of gypsum board as a fire-resistance tool indicates that the three components of the board—face paper, core and back paper—need to come into play in order for ultimate effectiveness to be achieved. The use of adhesives to hold the ceiling in place doesn’t include two of these three components. For the past two years, the burden of proof has been on the fire service to demonstrate that these are legitimate concerns and issues impacting the safety and survival of building occupants and firefighters. Thanks to the efforts of Massachusetts building-code developers, that burden now shifts to the modular home industry to prove that what they’re doing across the country meets our profession’s higher standards. The battleground may have changed, but a beachhead has been secured. We encourage all fire chiefs to pursue this type of code change in their jurisdiction. Kevin A. Gallagher is the chief of the Acushnet (Mass.) Fire & EMS Department. He represents the Fire Chiefs Association of Massachusetts on an advisory committee to the state’s building code developers. |
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