Construction Concerns: Acquired Structures for Live Fire Training

Article and photos by Gregory Havel

When our fire departments or regional fire training schools have the opportunity, many accept acquired structures for live-fire training. Chapter 4 of the National Fire Protection (NFPA) Standard 1403, Live Fire Training Evolutions, 2007 edition, discusses in detail the requirements for structural, student, and instructor safety during live-fire training.

Lightweight components like wood trusses and I-joists have been in use for more than 30 years, both in new construction and in remodeling. It is likely that in the future we will be offered for training the use of one of these houses with lightweight structural members.

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Photo 1 shows the exposed joists in the basement of a remodeled house that was built in 1945. The joists on the left, part of the original structure, are 2 x 12 lumber measuring 1 5/8 x 11 5/8 inches. The two 2 x 12s nailed to the last lumber joist on the right measure 1 1/2 x 11 1/2 inches, the standard size since the 1960s.

The joists running at right angles from the triple joist in the center of the photo are manufactured I-joists, installed to close a stairway opening that is no longer used. The top and bottom members are laminated veneer lumber (LVL), and the web is oriented strand board (OSB). These I-joists are supported by galvanized sheet-metal joist hangers, nailed into the lumber joists at each end of the stairway opening.

The left side of photo 1 also shows the underside of the one-inch-thick tongue-and-groove subfloor boards that were laid at a 45° angle to the joists and nailed down. The finished floor in this part of the house is ¾-inch tongue-and-groove boards. The subfloor shown on the I-joists in the former stairway opening is ¾-inch thick plywood. (OSB is often used in place of plywood.) The position of the joist hangers was adjusted vertically so that the top surface of the plywood matched the top surface of the original one-inch subfloor boards. The subfloor was covered with carpet and pad.

The left side of photo 1 shows the type of sturdy floor to which we have become accustomed in acquired structures. The right side shows what we can expect in structures that have been built or remodeled in the past 30 years.

We know from books, magazine, and Web site articles, our personal experience, and the Underwriters Laboratories online short course “Structural Stability of Engineered Lumber in Fire Conditions” (http://www.ul.com/fire/structural.html), that the traditional type of construction shown on the left side of photo 1 retains its structural strength under fire conditions for a longer time than the modern type of construction shown on the right side of the photo.

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NFPA 1403.4.2.10 states: “All hazardous structural conditions shall be removed or repaired so as to not present a safety problem during use of the structure for live fire training evolutions.” A building with floors supported entirely by wood I-joists (photo 2) or by wood trusses (photo 3) has a hazardous structural condition so extensive that it cannot be repaired.

NFPA 1403.4.2.25 states that the “instructor-in-charge” is responsible for preparing a preburn plan showing the features in the training areas and in the structure; and for documenting fuel loading, including the type of construction of the structure, type of roof, and combustible void space; and for designating primary and secondary exit paths for participants in each fire area.
  
NFPA 1403.4.2.13 states “Buildings that cannot be made safe as required by this chapter shall not be utilized for interior live fire training evolutions.”

What does this mean for us when we consider acquiring a structure for live-fire training?

  • An evaluation of the structure must be completed before it is accepted from the owner, including inspection of floor and roof support systems, void spaces, and any other features; including those added or changed by remodeling. This will involve making inspection openings in ceilings, which must be repaired if the structure is accepted for live-fire training.
  • A structure with all of its floors supported by wood trusses or I-joists must not be accepted for live-fire training because of its interconnected combustible void spaces, rapid burning characteristics, and potential for early and sudden collapse.
  • A structure with parts of its floors supported by wood trusses or I-joists may be acceptable for live-fire training, provided that these areas are not used in training; can be isolated to prevent student or instructor entry; will not endanger the structural stability of the rest of the building if they should collapse; and that the presence of these areas is included in the briefings for both instructors and students.
  • A structure with a roof supported by wood trusses or I-joists may be acceptable for live-fire training, provided that roof ventilation openings are cut before the training begins, as required by NFPA 1403, Chapter 4; the presence of the truss-supported roof is included in the briefings for both instructors and students; and that extra precautions are taken, including exterior observers of the roof structure and inspections of the roof structure between room fires, to ensure instructor and student safety.

 

   

Gregory Havel is a member of the Burlington (WI) Fire Department; a retired deputy chief and training officer; and a 30-year veteran of the fire service. He is a Wisconsin-certified fire instructor II and fire officer II, an adjunct instructor in fire service programs at Gateway Technical College, and safety director for Scherrer Construction Co., Inc. Havel has a bachelor’s degree from St. Norbert College; has more than 30 years of experience in facilities management and building construction; and has presented classes at FDIC.

 

Subjects: Building construction for firefighters

FE Category: Prevention and Protection, Building Construction

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