Chapter 3: Use and Occupancy Classification

1 2015 international building code COMMENTARY3-1 Chapter 3:Use and Occupancy ClassificationGeneral CommentsChapter 3 provides for the Classification of buildings,structures and parts thereof based on the purpose orpurposes for which they are 302 identifies the Occupancy groups intowhich all buildings, structures and parts thereof must 303 through 312 identify the occupancycharacteristics of each group Classification . In somesections, specific group classifications having require-ments in common are collectively organized such thatone term applies to all. For example, Groups A-1, A-2,A-3, A-4 and A-5 are individual groups. The generalterm Group A, however, includes each of these individ-ual groups. For this reason, each specific assemblygroup Classification is included in Section 303.

2 Definitions play a key role in determining the occu-pancy Classification . All definitions are located in Chap-ter 2. This Chapter lists key definitions for classificationof occupancies. In the early years of building code development, theessence of regulatory safeguards from fire was to pro-vide a reasonable level of protection to property. Theidea was that if property was adequately protected fromfire, then the building occupants would also be this outlook on fire safety, the concept of equiv-alent risk has evolved in the code . This concept main-tains that, in part, an acceptable level of risk against thedamages of fire respective to a particular occupancytype (group) can be achieved by limiting the height andarea of buildings containing such occupancies accord-ing to the building 's construction type ( , its relativefire endurance).

3 The concept of equivalent risk involves three interde-pendent considerations: 1. The level of fire hazard asso-ciated with the specific Occupancy of the facility; 2. Thereduction of fire hazard by limiting the floor areas andthe height of the building based on the fuel load (com-bustible contents and burnable building components);and 3. The level of overall fire resistance provided bythe type of construction used for the interdependence of these fire safety consider-ations can be seen by first looking at Tables 601 and602, which show the fire-resistance ratings of the princi-pal structural elements comprising a building in relationto the five classifications for types of construction. TypeI construction is the Classification that generally requiresthe highest fire-resistance ratings for structural ele-ments, whereas Type V construction, which is desig-nated as a combustible type of construction, generallyrequires the least amount of fire-resistance-rated struc-tural elements.

4 If one then looks at Tables , , the relationship among group Classification ,allowable heights and areas and types of constructionbecomes apparent. Respective to each group classifica-tion, the greater the fire-resistance rating of structuralelements, as represented by the type of construction,the greater the floor area and height allowances. Thegreater the potential fire hazards indicated as a functionof the group, the lesser the height and area allowancesfor a particular construction a result of extensive research and advancementsin fire technology, today s building codes are more com-prehensive and complex regulatory instruments thanthey were in the earlier years of code the principle of equivalent risk remains an impor-tant component in building codes, perspectives havechanged and life safety is now the paramount fire so, Occupancy Classification still plays a key partin organizing and prescribing the appropriate protectionmeasures.

5 As such, threshold requirements for fire pro-tection and means of egress systems are based onoccupancy Classification (see Chapters 9 and 10).Other sections of the code also contain requirementsrespective to the Classification of building groups. Forexample, Section 705 addresses requirements for exte-rior wall fire-resistance ratings that are tied to the occu-pancy Classification of a building and Section interior finish requirements that are dependentupon the Occupancy classificationPurposeThe purpose of this Chapter is to classify a building ,structure or part thereof into a group based on the spe-cific purpose for which it is designed or the code , group classifications are consid-ered a fundamental principle in organizing and prescrib-ing the appropriate features of construction andoccupant safety requirements for buildings, especiallygeneral building limitations, means of egress.

6 Fire pro-tection systems and interior AND Occupancy CLASSIFICATION3-22015 international building code COMMENTARYSECTION Scope. The provisions of this Chapter shall control theclassification of all buildings and structures as to use andoccupancy. As used throughout the code , the Classification of anoccupancy into a group is established by the require-ments of this Chapter . The purpose of these provi-sions is to provide rational criteria for theclassification of various occupancies into groupsbased on their relative fire hazard and life safetyproperties. This is necessary because the code uti-lizes group Classification as a fundamental principlefor differentiating requirements in other parts of thecode related to fire and life safety General.

7 Structures or portions of structures shall beclassified with respect to Occupancy in one or more of thegroups listed in this section. A room or space that is intendedto be occupied at different times for different purposes shallcomply with all of the requirements that are applicable toeach of the purposes for which the room or space will beoccupied. Structures with multiple occupancies or uses shallcomply with Section 508. Where a structure is proposed for apurpose that is not specifically provided for in this code , suchstructure shall be classified in the group that the occupancymost nearly resembles, according to the fire safety and rela-tive hazard Assembly (see Section 303): Groups A-1, A-2, A-3,A-4 and Business (see Section 304): Group Educational (see Section 305): Group Factory and Industrial (see Section 306): Groups F-1and High Hazard (see Section 307): Groups H-1, H-2, H-3,H-4 and Institutional (see Section 308): Groups I-1, I-2, I-3and Mercantile (see Section 309): Group Residential (see Section 310): Groups R-1, R-2, R-3and Storage (see Section 311): Groups S-1 and Utility and Miscellaneous (see Section 312): GroupU.

8 This section requires all structures to be classified inone or more of the groups listed according to thestructure's purpose and function ( , its Occupancy ).By organizing occupancies with similar fire hazardand life safety properties into groups, the code hasincorporated the means to differentiate occupanciessuch that various fire protection and life safetyrequirements can be rationally organized andapplied. Each specific group has an individual classi-fication. Each represents a different characteristicand level of fire hazard that requires special codeprovisions to lessen the associated risks. There aresome group classifications that are very closelyrelated to other specific groups and, therefore, arecollectively referred to as a single group ( , GroupF applies to Groups F-1 and F-2).

9 In these cases,there are requirements within the code that are com-mon to each specific group Classification . These com-mon requirements are applicable based on thereference to the collective Classification . For example,the automatic sprinkler system requirement of Sec-tion applies to each specific group classifica-tion (R-1, R-2, R-3 and R-4) listed under the term Group R. Although many requirements applicable toa general Occupancy Classification are the same forall of the subclassifications within the occupancygroup, there are enough differences to warrant thedivision of the general category into two or more spe-cific : Both a restaurant (Group A-2) and achurch (Group A-3) are included in Group A, but theyhave different specific group classifications.

10 BothGroups A-2 and A-3 are subject to the same traveldistance limitations (see Table ) and corridorfire-resistance ratings (see Table ), but havedifferent thresholds for when automatic sprinkler sys-tems are required (see Section 903).Buildings that contain more than one occupancygroup are mixed Occupancy buildings. Buildings withmixed occupancies must comply with one of thedesign options contained in Section 508. Optionsestablished in Section 508 include the regulation ofthe mixed- Occupancy conditions as accessory occu-pancies, nonseparated occupancies or , a building or space is intended to beoccupied for completely different purposes at differ-ent times. For instance, a church hall might be usedas a day care center during weekdays and as areception hall for weddings and other similar eventsat other times.