Building Construction Related to the Fire Service Chapter 2 — Structural Fire Resistance and Building Classifications

Building Construction Learning Objective 1 Define fire resistance. Building Construction

Building Construction Fire Resistance Function of the properties of all materials used; includes combustibility, thermal conductivity, chemical composition, density, and dimensions Ability of a structural assembly to maintain load-bearing and structural integrity under fire conditions (Continued) Building Construction

Building Construction Fire Resistance Ability of walls, partitions, and ceilings to act as a fire barrier Fire resistance rating Expressed in hours and fractions of hours Incorporated into construction classifications and building codes Building Construction

Building Construction Learning Objective 2 Discuss methods of determining fire resistance and the limitations of each method. Building Construction

Determination of Fire Resistance Conducting standard fire resistance testing in a laboratory Performing analytical calculations to determine the resistance to a standard fire test exposure Employing analytical structural fire engineering design methods based on real fire exposure characteristics Building Construction

Fire Resistance Test Method Laboratory test is most commonly used method Component subject to heat of a standard fire in test furnace Primary points of failure for test Fire resistance ratings expressed in standard intervals (Continued) Building Construction

Fire Resistance Test Method Factors impacting fire resistance ratings from standard test Standard fire test evaluates ability of structural assemblies to carry a structural load and act as a fire barrier Information NOT provided by test Assemblies may be penetrated (Continued) Building Construction

Building Construction Learning Objective 3 Identify fire testing organizations and discuss the significance of fire test results. Building Construction

Fire Testing Organizations Testing for fire resistance ratings is beyond capability of local fire and building departments Several laboratories are equipped to conduct testing Some organizations use furnaces primarily for research and product development Building Construction

Building Construction Fire Test Results Published by testing laboratories Deviation from materials or dimensions specified alters test results Building Construction

Building Construction Learning Objective 4 Recognize the role of analysis in determining fire resistance. Building Construction

Analytical Design Using Real Fire Exposures NFPA® 251 test Most commonly used May be too severe or not severe enough Ratings determined analytically using a different time-temperature curve must be interpreted cautiously Building Construction

Noncombustible Materials Building codes contain explicit criteria for determining combustible material Incapable of supporting combustion under normal circumstances Most common test for determining combustibility – ASTM E 136 Building Construction

Building Construction Learning Objective 5 Discuss the basic building classifications as they relate to fire resistance. Building Construction

Building Construction Classifications Type I, Fire-Resistive Type II, Noncombustible Type III, Masonry (Exterior protected) Type IV, Heavy timber Type V, Wood frame (Continued) Building Construction

Building Construction Classifications In building codes, based on materials used in construction and hourly fire resistance ratings required for structural components Building Construction

Building Construction Type I Construction Structural members are noncombustible construction with a specified fire resistance Combustible material typically permitted in certain components Most common methods of construction Building Construction

Building Construction Type II Construction Noncombustible – Can be either protected or unprotected Material other than steel can be used Building codes allow combustible material similar to that in Type I (Continued) Building Construction

Building Construction Type II Construction Unprotected, noncombustible building cannot be expected to provide structural stability under fire conditions Point at which unprotected members will fail depends on several factors Protected, noncombustible structural fire protection is similar to Type I Building Construction

Building Construction Type III Construction “Ordinary construction” Exterior walls frequently masonry, but can be any noncombustible material with required fire resistance Interior members Partially or wholly combustible Protected or unprotected (Continued) Building Construction

Building Construction Type III Construction Building Construction

Building Construction Type IV Construction “Mill construction” Difference from Type III Used in older factories, mills, and warehouses Primary fire hazard – Massive amount of fuel from large structural members Courtesy of McKinney (TX) Fire Department Building Construction

Building Construction Type V Construction All structural components may be combustible Two subclassifications Differences from Type III Threat to adjacent structures if heavily involved in fire Building Construction

Building Construction Mixed Construction Some buildings are allowed a mixed construction type May result in special challenges for emergency responders Building Construction

Building Construction Learning Objective 6 Discuss the concept of fire load and its impact on building construction types. Building Construction

Building Construction Fire Load Maximum heat released if all available fuel in a building was consumed Product of weight of combustibles multiplied by their heat of combustion Expressed in lb/sq ft (kg/sq m) Varies depending on heat of combustion of fuel Building Construction

Building Construction Heavy Fire Load Building Construction

Fire Load and Construction Type Buildings with combustible structural components have greater fire load than Type I and II Fire load does not translate into equivalent structural load Building Construction

Building Construction Learning Objective 7 Explain occupancy classifications as they relate to fire risks. Building Construction

Occupancy Classifications Assign building occupancies into groups with broadly similar fire risks Building Construction

Building Construction IBC® Classifications Group A – Assembly Group B – Business Group E – Education Group F – Factories Group H – High Hazard Group I – Institutional Group M – Mercantile Group R – Residential Group S – Storage Group U – Utility and Misc. Building Construction

Building Construction Mixed Occupancies Buildings may contain more than one occupancy classification Codes require fire-resistive separations between various occupancies Requirements depend on local code Reduction in occupancy separation may be permitted if building is sprinklered Building Construction

Building Construction Change of Occupancy Frequently occurs Can create problems May require expensive renovations that owner not willing to pay Building Construction

Building Construction Summary Fire behavior in buildings is determined largely by construction materials and structural fire resistance. Structural fire resistance is determined most often through laboratory testing. (Continued) Building Construction

Building Construction Summary Building codes classify construction into types based on construction material, structural fire resistance, and occupancy. Occupancies within individual occupancy groups present roughly similar fire risk factors. Building Construction

Building Construction Review Questions 1. What is fire resistance? 2. What is the value of standard fire tests? 3. What is a noncombustible material? 4. What considerations do firefighters need to take into account when they encounter dropped ceilings? (Continued) Building Construction

Building Construction Review Questions 5. What are the major occupancy classifications contained in the International Building Code® (IBC®)? Building Construction