sures, smoke barriers, floors, ceilings, and roofs. Fire ratings are based on the number of hours a building element will resist fire before it is adversely affected by the flame, heat, or hot gases.
All buildings are classified into one of five or six types of construction. Type I buildings are the most fire-resistive and typically contain structural members that are noncombustible. Type I buildings also have the highest fire rating, usually 2 to 4 hours. Type V buildings (Type VI in the SBCCI codes) have the lowest fire rating and are typically of wood-frame construction.
Adjuncts to Building Codes
Building codes typically have additional companion codes and standards that govern other aspects of construction, which, with the exception of the electrical code, are usually published by the same group that publishes the model building codes.
Model codes frequently use industry standards developed by trade associations, government agencies, and standards-writing agencies such as the American Society for Testing and Materials (ASTM), the American National Standards Institute (ANSI), and the National Fire Protection Association (NFPA). Building codes reference these standards by name, number, and date of latest revision and become law when a code is accepted by a jurisdiction. In addition, there may be local jurisdictions that maintain energy-conservation codes, health and hospital codes, fabric flammability regulations, and codes that regulate construction and finishes.
Test Ratings and Fire-Resistant Materials and Finishes
It is estimated that roughly 75 percent of all codes deal with fire and life-safety issues, and the primary aim of fire codes is to confine a fire to its area of origin, thus limiting its spread and preventing flashover. To facilitate this, all approved materials and construction assemblies referred to in building codes are assigned ratings based on standardized testing procedures. The rating of an assembly is ascertained by evaluating its performance during testing and by examining its fire-resistive properties. There are hundreds of standardized tests for building materials and construction assemblies.
Any approved testing laboratory can undertake the testing of building materials, provided that standardized procedures are followed. The American Society for Testing and Materials (ASTM), the National Fire Protection Association (NFPA), and Underwriters Laboratories (UL), in collaboration with the American National Standards Institute (ANSI), are among the best-known organizations that have developed a large variety of standardized tests and testing procedures.
Upon being subjected to one of the standard tests, a material is given a rating based on its performance during the test. For construction assemblies tested according to ASTM E-119, the rating given is according to time—that is, how long an assembly will contain a fire, retain its structural integrity, or both. The test evaluates a construction assembly’s performance in the face of the temperature rise on the protected side of the assembly, the amount of smoke, gas, or flame that penetrates the assembly, and the assembly’s structural performance during exposure to fire. The ratings are 1-hour, 2-hour, 3-hour, and 4-hour; 20-, 30-, and 45- minute ratings are also used for doors and other opening assemblies. Assemblies that consultants and field observers must be concerned with include fire walls, fire-separation walls, shaft enclosures (such as stairways, exits, and elevators), floor/ceiling constructions, and doors and rated glazing.
Building codes typically have tables that stipulate the type of construction that meets the different hourly ratings. Thus, when a building code states that a 1-hour-rated partition assembly is required between an exit corridor and an adjoining tenant space, the designer must select and detail a design that incorporate the requirement for 1-hour construction.