This article concludes the two-part summary of the 54-page Chapter 3, "Wood Construction," of the 667-page third edition of my book, Building Construction For The Fire Service . Part 1 of "The Building Is Your Enemy" was published in Firehouse® February 1996, part 2 in August 1996, part 3 in...
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This article concludes the two-part summary of the 54-page Chapter 3, "Wood Construction," of the 667-page third edition of my book, Building Construction For The Fire Service. Part 1 of "The Building Is Your Enemy" was published in Firehouse® February 1996, part 2 in August 1996, part 3 in January 1997 and part 4 in February 1998.
Facts about structures are printed in regular type. Firefighting implications are printed in italics. Page references are to Building Construction For The Fire Service, third edition.
Beware of code definitions. Publications on building construction divide buildings into five nice, neat groups, which makes a good exam question. From the firefighter's point of view, however, these groups do not necessarily define the hazards or the fire characteristics of the building.
Heavy Timber Construction
This type of construction will be discussed further in future articles when we discuss ordinary construction, since the great majority of heavy timber buildings have masonry exterior bearing walls.
Illustration by Christopher Brannigan
This Maryland building appears to be of brick construction. The removal of the adjacent building, however, exposes the original log walls. Note the wood-stud wall above the logs. Know your buildings!
There are five general types of buildings; heavy timber is one. It is usually described in favorable terms, such as slow burning. Unfortunately, the generalized description of favorable characteristics does not apply to a great many such buildings. They have serious and life threatening hazards. Unless a building FULLY meets the description of mill construction on pages 204-207, it can be very dangerous to us.
After the Seattle tragedy in which four firefighters died in what was widely reported as a heavy timber building, I was asked many times, "How could this happen in a heavy timber building?" The answer was that the portion which collapsed was supported on a wood stud wall. Get the report on this fire from the U.S. Fire Administration (see U.S. Fire Administration Report No. 77, prepared by Gordon Routley of TriData Corp. Copies of the report are available without charge from the U.S. Fire Administration, 16825 S. Seton Ave., Emmitsburg, MD 21727). Read and heed it.
"Non-combustible" buildings, by code definition, may have substantial wood components, typically roofs and balconies. Fire-resistive buildings may have substantial areas of wood trim in restaurants and executive offices. Do not base pre-fire plans simply on the code, classification or a general description of the building.
Pre-fire planners should actively look for exceptions to the general characteristics. All should be alert for alterations. Analyze their possible effect on your life.
For a fuller description of the hazard of applying very general type descriptions to specific buildings see The NFPA Handbook, 18th edition, Section 10, Chapter 11, "Building Construction Concerns Of Fire Departments," by this author.
A serious problem in combustible construction is the combustible voids, usually interconnected, in which fire, like a cancer, can spread, involve the entire structure and often burst out violently, causing injury and death to firefighters.
Unfortunately, this deadly hazard is not taught in live fire training. In such training the fire is visible and the focus is to "put the wet stuff on the red stuff." The fire service should give better training on this deadly hazard.
The use of truss floors has greatly increased this hazard, since the trusses provide a void or "trussloft" in every floor. In order to get laws passed to provide sprinkler protection against flashover, partial sprinkler standards have been introduced for residential structures. On balance this is a good concept. However, such sprinklers are not effective against fire which starts in or penetrates into the void space. If the piping is plastic it may burn through and waste the water.