FDIC 2011 Classroom Warns of Dangers Posed by Modular Construction

On Thursday at FDIC 2011, Chief Kevin A. Gallagher of the Acushnet (MA) Fire & EMS Department delivered a classroom on the dangers firefighters face while operating at fires at prefabricated (modular) residential construction.

Gallagher recounted an incident involving a two-story modular home in his department's response area that spread rapidly and caused the department consternation, forcing them to investigate the cause of the fire. "My department couldn't shake this fire," said Gallagher. "What did we do or didn't we do?"

The fire prompted the department to look at certain construction techniques common to that industry but little known to the fire service. Modular homes are not manufactured homes (i.e. mobile homes), but classified as manufactured buildings, consisting of components that are preconstructed in assembly-line fashion in a factory then transported to the building site and put together.

The creation of large void spaces formed when the upper level boxes are placed on top of the lower level boxes can measure 48' x 14" x 20 inches in height. A fire entering these void spaces can travel unimpeded the full length of the structure. Simply put, it is "balloon frame construction on the horizontal plane.” Gallagher discussed relevant code requirements for void spaces and measures to reduce their overall change.

One part of the presentation that generated the most discussion and feedback (and a few sighs of disbelief) concerned the widespread use by the modular industry of polyurethane foam structural adhesives, which are used to secure gypsum board to the ceilings and partition walls.

An investigation determined:

  • The glue is highly flammable;
  • Often the glue is the only means of securing the ceiling to the wood framing;
  • The International Residential code allows the glue to be used as the sole means of securing the ceiling (no mechanical fasteners);
  • The standards used to secure authorization for the above does not test the product under fire conditions;
  • The glue begins to decompose at temperatures well below those found at the ceiling level in a room and contents fire.

The above means that firefighters can expect ceiling failure sooner than in traditional residential construction, and when it does the fire has a pathway into the void space that runs the full length of the building. Traditional tactics and strategies for fighting fires in residential structures will be challenged in modular constructed homes.

“The goal of the presentation is to introduce these issues to attendees, share building code changes we have made in Massachusetts, and generate an interest in being an advocate for change at their state and local level,” Gallagher said. “Most importantly, I hope to provide a heads-up on these common building techniques that provide us with uncommon hazards and place our firefighters at greater risk.”

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