Occupancy Classification and Use PDF

3 Occupancy Classification and Use The intended use or occupancy of a building is a fundamental consideration for the building code. Typically, a client comes to an architect with a defined need for a facility. The desired use of that facility determines the occupancy group to which it is assigned...

3 Occupancy Classification and Use The intended use or occupancy of a building is a fundamental consideration for the building code. Typically, a client comes to an architect with a defined need for a facility. The desired use of that facility determines the occupancy group to which it is assigned under the code. Occupancy group classifications trigger specific requirements for the allowable area and height of a building, for means of egress, as well as for type of construction. The “I” codes are fundamentally occupancy based, as were the three model codes from which it was born. Most other broad sets of code criteria are derived from the basic classification by occupancy. The code separates uses into broad groups called occupancies. Under these groups are subdivisions that further refine the detailed requirements. It is worth remembering that while the designer usually makes the first pass at categorizing uses in terms of occupancy according to the fire safety and relative hazard involved, the ultimate judge of occupancy classification is the building official per the provisions of Chapter 1 of the IBC. The intent regarding classification is best described by the language directing classification of atypical occupancies: “Such structure shall be classified in the group which the occupancy most nearly resembles, according to the fire safety and relative hazard involved.” This reiterates the intent and purpose of the occupancy classifications that exist in the code. Each of the stated occupancy classifications was determined during the code development process by using fire-safety and relative hazard performance data to develop criteria. The IBC contains “User Notes.” At the beginning of Chapter 3, these state that “Chapter 3 provides the criteria by which buildings and structures are classified into use groups and occupancies. Through the balance of the code, occupancy classification is fundamental in the setting of features of construction; occupant safety requirements, especially building limitations; means of egress; fire protection systems; and interior finishes.” OCCUPANCY CLASSIFICATION Determination of the occupancy type flows in almost every case from the program given to the designer by the client. Other code requirements flow from the number of occupants and the hazards to their safety from external and internal factors. Along with life safety concerns, the code looks at property protection considerations. The occupancy’s hazards are assessed relative to their impact on adjacent properties as well as on the building occupants. The code also analyzes the hazards posed by adjacent buildings; however, it places the responsibility for protection of the adjacent facilities on the building under consideration. Several ideas common to most occupancy classifications, discussed in detail in Chapter 5, should be understood. First is the language: “structures or portions of structures.” This distinction allows the use of mixed occupancies in a single building without having to consider the entire building as a single occupancy group. The concept of “separated” and “nonseparated” uses, discussed in Chapter 5, allows the designer two options for addressing mixed-use buildings. It also allows rooms within buildings to be considered as distinct occupancies that can then be addressed as either separated or nonseparated uses at the designer’s discretion. Among the considerations for occupancy classification are: how many people will be using a facility; whether there are assembly areas such as theaters and restaurants; whether people will be awake or asleep in the building; will they be drinking alcohol while using the building, or undergoing medical treatment, which makes them less capable of self-preservation in an emergency? The presence of hazardous materials or processes will also affect the requirements for allowable area, fire separations, and construction type. The other concept to understand is that the laundry lists of examples in each occupancy group are not the sole definition of which uses are to be classified in which occupancy group. The code recognizes that not all occupancies are included in the lists and gives direction to the designer and the building official regarding classification of buildings not included in the examples. Note that the criteria discussed in this book generally apply to non-hazardous occupancies. Hazardous occupancies are not encountered by most design professionals and are covered by a separate set of special requirements discussed in § 414 and § 415. Because they are very specialized and encountered infrequently by most designers, the requirements for hazardous occupancies will only be lightly touched on in this book. It is essential to read the detailed requirements for each type of occupancy in a project. There are often cross-references to various other code sections in the detailed occupancy criteria. Another factor that impacts occupancy classification is the mixture of various uses in a building and their sizes relative to the predominant use of the building. The sections regarding mixed occupancies and incidental uses are not found in Chapter 3 but are located in Chapter 5 of the IBC. The IBC establishes the following occupancy groups: • Assembly (A) • Business (B) • Educational (E) • Factory and Industrial (F) • High Hazard (H) • Institutional (I) • Mercantile (M) • Residential (R) • Storage (S) • Utility and Miscellaneous (U) Code users often speak of “uses and occupancies” when describing what goes on in a building. The code introduces a discussion of “uses” in § 302.2. Occupancy group descriptions contain uses considered to have similar hazards and risks to building occupants. Uses often also have additional requirements described in Chapter 4. We recommend first identifying uses in lay terms, then looking in the descriptions of uses in Chapter 3 that are associated with various occupancies to help determine the proper occupancy classification. 20 / BUILDING CODES ILLUSTRATED—THE BASICS Assembly Group A (303) The examples noted in this group recognize that these uses bring large groups of people together in relatively small spaces. How the spaces are used in relationship to physical features and human behavior also enter into the distinction between assembly categories, which are meant to serve as cues for assigning buildings or parts of buildings to an occupancy class. The final determination of this classification, as for all classifications, is made by the building official. Note that the subcategories are examples, not a definitive or exhaustive list of possible assignments. Be very careful in reading language where criteria are based on numbers. “Less than 50 persons” means that 49 or fewer people have one set of criteria and “50 or more” have another. The dividing line in this case is 50. Read such language very carefully when deciding if an issue belongs in one category or another. If in doubt, be sure to verify the interpretation with your AHJ early in the design process to avoid costly errors. Group A occupancies are typically defined as having 50 or more occupants, but the use of the space must be examined in relation to the code language stating that these are spaces “for purposes such as civic, social or religious functions, recreation, food or drink consumption…” For instance, retail stores in M occupancies may have more than 49 occupants but are not considered as Group A. Per § 303.1.1, assembly areas with fewer than 50 occupants are to be classified as Group B occupancies. Assembly areas of less than 750 sf (69.68 m2) that are accessory to other uses are also not considered as Group A areas per § 303.1.2 Item 2. Language in § 303.1.3 clarifies that assembly occupancies associated with Group E occupancies (educational facilities) need not be considered as separate “A” occupancies. This is intended to avoid needing occupancy separations between school gymnasiums and classrooms. Accessory religious educational rooms and religious auditoriums with an occupant load of less than 100 are not considered separate occupancies and would be classified with the majority of the facility, likely as an A-3 occupancy. • Group A-1 per § 303.2 is for assembly areas, usually with fixed seats, intended for the viewing of performing arts or motion pictures. The presence or absence of a stage is not a distinguishing feature. The egress requirements in Group A-1 occupancies recognize that light levels may be low during performances and that people may panic in emergency situations under such circumstances. Group A: 50 or more occupants Group B: Less than 50 occupants OCCUPANCY GROUPS • Group A occupancies are typically defined as having 50 or more occupants, but per § 303.1.1, assembly areas with fewer than 50 occupants are to be classified as Group B occupancies. A-2 A-2 • Group A-2 per § 303.3 is for assembly areas where food and drink are consumed. The requirements for these occupancies presume that alcoholic beverages may be served, thus potentially impairing the occupants’ responses to an emergency. It also presumes that chairs and tables will be loose and may obstruct or make unclear egress pathways for patrons. The requirements also recognize the poor fire history of such occupancies. • Also, note that the code addresses commercial kitchens. They are to be classified in the same A-2 occupancy as the dining areas they are associated with. See “B” and “F” occupancies for a discussion regarding food processing facilities and commercial kitchens not associated with assembly spaces used for dining. • Group A-3 occupancies per § 303.4 are assembly areas that do not fit into the other Group A categories. It also includes spaces used for worship, recreation, or amusement. The intent of this classification is that any use that seems to be an assembly occupancy and does not fit the criteria of the other four Group A categories should be classified as an A-3 occupancy. • One notable item is the classification of greenhouses having public access for such uses as botanic gardens. Note that greenhouses used for the sale of plants are to be an “M” occupancy. USE AND OCCUPANCY / 21 OCCUPANCY GROUPS • Group A-4 occupancies per § 303.5 are assembly areas for the viewing of indoor sporting events. • Group A-5 occupancies per § 303.6 are assembly areas for the participation or viewing of outdoor sporting events. • The principal distinction between Group A-4 and A-5 occupancies is one of indoor versus outdoor facilities. Note also that Group A-4 occupancies are presumed to have spectator seating. Those assembly uses that are similar to these two classifications but do not meet all their criteria would most likely be considered Group A-3 occupancies. • As noted in § 303.1.2 Item 1, “small” assembly spaces with less than 50 occupants are to be considered by exclusion as part of the overall occupancy. For example, having a conference room or a lunchroom with fewer than 50 occupants serving a larger use does not trigger classifying that space as an Assembly Group A occupancy. • Per the same criteria, a large conference room in an office, where the room has more than 49 occupants, would be classified as an A-3 occupancy. This may trigger code provisions related to Group A occupancies that might not otherwise apply to the other office areas. It also may trigger occupancy separation requirements per § 508.4. 22 / BUILDING CODES ILLUSTRATED—THE BASICS OCCUPANCY GROUPS Business Group B Office buildings are typically classified as Group B occupancies. Storage areas for offices, such as back-office file rooms, do not constitute a separate occupancy. Outpatient clinics and ambulatory care facilities are also classified in this occupancy group. “Clinic-outpatient” defines a medical care facility where patients are not rendered incapable of self-preservation. Even where patients may be rendered incapable of unassisted self-preservation by anesthesia, the use could still be classified as a Group B occupancy. Such a facility, called an “ambulatory care facility,” is contained in the B occupancy list. It is defined in Chapter 2 as being a facility where patients stay for less than 24 hours but where such patients are rendered incapable of self-preservation. The definition refers only to “care“ facilities to broaden the applicability of this occupancy classification to more uses. Testing and research laboratories that do not exceed the quantities of hazardous materials specified in the code are also classified as Group B occupancies. Those that exceed the quantity limits are classified as Group H occupancies. Educational facilities for junior colleges, universities, and continuing education for classes above the 12th grade are considered Group B occupancies, not Group E. Assembly rooms in these facilities should be examined for conformance with the criteria for Group A occupancies. Note that procedures such as laser eye surgery or kidney dialysis should be considered as rendering patients incapable of unassisted self-preservation. Note further that facilities accommodating people incapable of unassisted self-preservation may also be classified as I-2 occupancies, based on duration of stay. P i z z a Take Out • Small food-processing facilities, such as a take-out-only pizza shop or to-go Asian food restaurant where there are no dining or drinking areas and that are no more than 2,500 sf (232 m2) in area, are to be classified as Group B occupancies instead of an A-2 or an F-1. Stand-alone food processing facilities that are larger than 2,500 sf are to be classified as Group F-1. USE AND OCCUPANCY / 23 OCCUPANCY GROUPS Educational Group E Group-E occupancies are used by six or more people for classes up to the 12th grade. Uses for the day care of six or more children over 2 1/2 years of age make up another set of Group-E occupancies. Day care uses with fewer than six children are to be classified with the larger occupancy they occur within. Those uses with fewer than six children in a dwelling unit are classified as Group R-3. Assembly uses in school facilities are not excluded from this use group. However, most schools use their large rooms for assembly uses. Such facilities need not be considered as separate A occupancies per the provisions of § 303.1.3. Religious classrooms and auditoriums that are accessory to churches and have fewer than 100 occupants are to be considered as A-3 occupancies per § 303.1.4. Factory and Industrial Group F Factory occupancies are defined in part by what they are not. The two occupancy groups, Moderate-Hazard Occupancy F-1 and LowHazard Occupancy F-2, are based on an analysis of the relative hazards of the operations in these occupancies and a determination that they do not fall under the criteria set for Group H. Group F-1 is classified as those operations not falling within the definitions for Group F-2. The predominant difference between F-1 and F-2 is that in F-2 occupancies the materials of manufacture are considered to be noncombustible. The classification of Group F occupancies assumes that these are not public areas. The users are presumed to be familiar with their surroundings and not occasional visitors. The processes themselves will determine which classification the use is to receive. Uses meeting the F-2 classification are limited. Occupancy classification determinations between Groups F-1 and F-2 often are done by a process of elimination. When analyzing whether a use or occupancy should be classified as Group F-1 or F-2, the quantities of materials used in the process under consideration will determine to which group the use belongs. For example, an F occupancy manufacturing alcoholic beverages up to 16% alcohol content is considered to be an F-2 low-hazard occupancy, while those manufacturing beverages with an alcohol content above 16% are an F-1 occupancy. This is based on the idea that the presumed level of flammability of such beverages increases with alcohol content, with 16% being established as the threshold between conventionally fermented wines and wines “fortified” with added alcohol. Large commercial cooking operations not associated with restaurants are called out to be F-1 occupancies. The code places a threshold of 2,500 sf (232 m2) for F-1 food-processing establishments and commercial kitchens. Facilities not exceeding the threshold, such as take-out restaurants with no seating or serving areas, are now called out to be classified as Group B occupancies. 24 / BUILDING CODES ILLUSTRATED—THE BASICS High-Hazard Group H Hazardous occupancies could easily be the subject of another book and will only be touched on in an introductory fashion in this text. The uses classified under this occupancy group are very specialized and require careful code and design analysis. Understanding the products, processes, hazard levels of materials used in the occupancy, and their quantities is essential. Variations in material quantities and hazards interact to set the design criteria for hazardous occupancies. The classification of uses in this category will almost undoubtedly require consultation with the client and with the building official at an early stage of design. There are two sets of criteria for hazardous occupancies. The first set is related to the hazard of the materials in use and the quantities of those materials in use. High-Hazard Groups H-1 through H-4 fall in this category. The second set relates to the nature of the use as well as the quantity and nature of hazardous materials in use. This is for High-Hazard Group H-5, which are semiconductor fabrication facilities and similar research and development facilities. Areas that contain limited quantities of hazardous materials may occur in other occupancy groups when the amounts are less than the “maximum allowable quantities” (MAQ). For example, small amounts of flammable cleaning fluids or paints might be stored in a room in a business occupancy. A mercantile occupancy can sell specified quantities of materials that may be considered hazardous without being designated a Group H occupancy as long as the amount of material is below the maximum allowable quantity. This exemption pertains only to occupancy classification related to quantities; it does not waive compliance with any other code provisions. Note also that the International Fire Code sets forth many additional construction and use requirements for Group H. OCCUPANCY GROUPS Control Areas The other basic concept in the code provisions for High-Hazard Group H is that of control areas. The special detailed requirements for the separation of control areas are contained in Chapter 4 and outlined in Table 414.2.2. Chapter 4 must therefore be read in concert with Chapter 3 to determine all applicable code requirements. This applies both to subdivisions of buildings classified as hazardous occupancies and to areas where hazardous materials occur within other occupancies. The definition of this concept bears stating verbatim from § 202: • Control areas are “spaces within a building where quantities of hazardous materials not exceeding the maximum allowable quantities per control area are stored, dispensed, used or handled.” • The control area concept allows multiple parts of a building to contain an array of hazardous materials when the areas are properly separated and the quantity of materials within each area meet the specified maximums for each type of material. These criteria reinforce the concept that hazard levels are mitigated by passive and/or active fire-protection measures. This concept is based on two primary considerations. The first is the nature of the hazard of the material in question. The second is that the level of hazard is primarily related to the quantity of materials within a given area. • Control areas must be separated from one another by 1-hour fire-barrier walls and floors having a minimum fire-resistance rating of 2 hours. For the fourth and succeeding floors above grade, fire-barrier walls must have a 2-hour fire-resistance rating. • Note that both the percentage of maximum allowable quantity of hazardous materials and the number of control areas decrease when proceeding up or down in the building to floors either above or below the first floor of a building. • Higher than nine floors above grade, one control area with 5% of allowable quantity is permitted per floor. • The seventh through ninth floors above grade may have two control areas per floor with 5% of allowable quantity per control area. 11 10 • The fourth through sixth floors above grade may have two control areas per floor with 12.5% of allowable quantity per control area. 9 8 • Third floor above grade may have two control areas with 50% of allowable quantity per control area. • The second floor above grade and first floor below grade may have three control areas with 75% of allowable quantity per control area. 7 6 5 4 3 2 1 B1 B2 B3 X X • The second floor below grade may have two control areas with 50% of the allowable quantity per control area. • Control areas are not allowed more than two floors below grade. USE AND OCCUPANCY / 25 OCCUPANCY GROUPS Institutional Group I Institutional occupancies are those where people have special restrictions placed on them. The occupancy groups in these groups are subdivided by the abilities of the occupants to take care of themselves in an emergency. The different categories in this occupancy are determined by the number of occupants, their ages, health and personal liberty, and whether they are in the facility all day or part of the day or night. Whether or not the occupants are capable of unassisted self-preservation or are somehow incapacitated to the extent they will need help to escape danger also enters into the occupancy classification. Many of these occupancy groups have a residential character, and if they fall outside the designated thresholds for Group I occupancies, they will likely be classified as residential occupancies. • 24-hour supervision • I-1 occupancies have been broken down into two “conditions” based on the abilities of the occupants to respond to emergencies and evacuate a building. The conditions are as follows: * Condition 1 occupants are presumed to be able to respond to an emergency independently and without assistance. * Condition 2 occupants are presumed to need “limited verbal or physical assistance” to respond to an emergency and evacuate the building. • Alarmed exit Group I-1, Condition 1 The different Group I occupancies have their distinguishing characteristics shown here in the same order to facilitate understanding the differences between them. • Group I-1 has more than 16 people living under supervised conditions and receiving custodial care in a residential environment on a 24-hour basis. “Custodial Care” is defined in § 202 as “Assistance with day-to-day living tasks, such as assistance with cooking, taking medication, bathing, using toilet facilities, and other tasks of daily living.” Custodial care includes persons receiving care who have the ability to respond to emergency situations and evacuate at a slower rate and/or who have mental and psychiatric complications. This classification includes halfway houses, assisted-living facilities, and group homes. • Unassisted response to an emergency situation • Smoke detection and barriers • Staff assistance Group I-1, Condition 2 • Alarmed exit, sprinklers, and story limit • 24-hour supervision • It is essential that the designer and the building client confer early in the design process to assess the capabilities of the prospective building occupants to determine the correct classification. This should also include consultation with the operator of the facility to determine what local licensing requirements may apply to the facility to assist in determining the proper classification. • Because the occupants under Condition 2 will likely take more time to evacuate the building during an emergency, the code places additional limitations for such things as the number of stories allowable for a given construction type, as well as requirements for smoke barriers, sprinkler protection, and smoke detection. If the 26 / BUILDING CODES ILLUSTRATED—THE BASICS understanding of the classification of the two conditions occurs late in the design process or in the course of construction, the change can have profound consequences on the building. Thus, it is important to make this determination early in the design process. If there is any doubt about how the building will be used, it is prudent to assume it will have to meet Condition 2 criteria, which would allow the use of the building by Condition 1 occupants. The reverse would not be the case. Condition 2 occupants could not be housed in a Condition 1 facility. • Similar occupancies with between 6 and 16 occupants are to be classified as an R-4 occupancy, or an R-3 if there are five or fewer occupants. OCCUPANCY GROUPS • Walls between units to be fire partitions per § 708. • Where sleeping units include private bathrooms, walls between bedrooms and the associated private bathrooms are not required to be constructed as fire partitions. • Corridor walls per Table 1020.2. I-1 I-1 I-1 • There are pointers for I-1 occupancies in § 420 that call out special conditions for multiple-dwelling-unit buildings, such as the fire separation of units from each other. I-1 I-1 I-1 • Assisted response to an emergency situation • 24-hour supervision • Staff assistance • Wide exit Group I-2, Condition 1 • Group I-2 has more than five people living under supervised conditions and medical care on a 24-hour basis. The occupants are presumed under this classification to be incapable of unassisted self-preservation and thus cannot respond to emergencies without assistance from the staff. This classification includes hospitals, mental hospitals, detox facilities, and nursing homes. Group I-2 occupancies are classified into two conditions. The conditions are as follows: § 308.3.1.1, Condition 1. This occupancy condition includes facilities that provide nursing and medical care but do not provide services typically associated with hospitals. This is considered to include nursing homes and foster care facilities. • Assisted response to an emergency situation • 24-hour supervision • Hospital services • Staff assistance • Wide exit Group I-2, Condition 2 • 24-hour supervision or • Less than 24-hour care • Supervisor • Residents Group R-3 under Certain Conditions § 308.3.1.2, Condition 2. This occupancy condition is for hospitals, and includes facilities that provide nursing and medical care and could provide emergency care, surgery, obstetrics, or in-patient stabilization units for psychiatric or detoxification. Similar occupancies with fewer than six occupants or who stay for less than 24 hours are to be classified as R-3 occupancies. They may also comply with the International Residential Code (IRC). The designer should verify the anticipated uses with the facility operator when making occupancy classifications. This should also be reviewed with the AHJ for their concurrence. Such facilities are to be fully sprinklered. USE AND OCCUPANCY / 27 OCCUPANCY GROUPS • 24-hour supervision • Controlled exit • Group I-3 has more than five people living under supervised conditions under restraint or security on a 24-hour basis. The occupants cannot respond to emergencies without assistance from the staff, not because of illness, infirmity, or age, but due to security measures outside their control. This group includes prisons, detention centers, and mental hospitals, and is further subdivided into five conditions based on the relative freedom of movement within areas inside the facility. These conditions also presume the areas are divided into smoke compartments with differing degrees of access controls between them. • Group I-4 is for uses having more than five people under supervised conditions and under custodial care on a less than 24-hour basis. The occupants are presumed not to be able to respond to emergencies without assistance from the staff, although this is not stated in the code. This classification includes adult day care and child day care. The group is further subdivided into care facilities for adults and for children under 2 1/2 years of age. A child day-care facility for between 6 and 100 children under 2 1/2 years of age, located on the exit discharge level with a direct exterior exit, is to be classified as an E occupancy. • Less than 24-hour care • Less than 24-hour care 28 / BUILDING CODES ILLUSTRATED—THE BASICS • Controlled exit Similar occupancies with five or fewer occupants may be classified as part of the primary occupancy, or if located within a dwelling unit, be classified as an R-3 occupancy or shall comply with the International Residential Code. OCCUPANCY GROUPS Mercantile Group M Uses in this group are fairly self-explanatory. The occupancy group includes accessory storage, which will be regulated per the mixed use provisions in § 508. Accessory occupancies are regulated by § 508.2 and must still be individually classified. Larger storage areas would be classified as Group S. Typically for larger combinations of M and S occupancies, the nonseparated provisions of § 508.3 are used. Most retail facilities, no matter what merchandise they sell, fall into this occupancy. “Greenhouses for display and sale of plants that provide public access” are to be classified as an M occupancy. There are limits to the quantities of hazardous materials that may be stored in mercantile occupancies without being classified as a Group H occupancy. These limits are shown in Table 414.2.5(1). USE AND OCCUPANCY / 29 OCCUPANCY GROUPS Residential Group R Residential occupancies include typical housing units, distinguished mainly by the total number of occupants. A key criterion for this type of occupancy is that the occupants sleep in the building. This group also includes smaller-scale institutional occupancies that fall below certain thresholds for the number of occupants. • Note that although defined terms related to residential occupancies are listed in the residential occupancy section, the definitions are in Chapter 2 and thus apply not only to this section but also throughout the code. S M T W T F 1 2 3 4 5 6 S 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 • Group R-1 occupants are transient, sleeping in their rooms for 30 days or less, as in hotels and transient boarding houses. The requirements assume that the occupants are not familiar with the surroundings. • Less than 31 days occupancy S M T W T F 1 2 3 4 5 6 S 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 S M T W T F S 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 • Permanent residency 30 / BUILDING CODES ILLUSTRATED—THE BASICS • Group R-2 occupants are permanent, sleeping in buildings containing more than two dwelling units for more than 30 days. These include apartments, dormitories, and long-term residential boarding houses. Congregate living facilities with more than 16 occupants are to be classified as R-2 occupancies. OCCUPANCY GROUPS S M T W T F 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 S M T W T F S 1 2 3 4 5 • Group R-3 occupants are permanent, and the group is defined as being those not meeting the criteria for R-1, R-2, R-4, or Group I occupancy groups. These include single-family residences and duplexes. Care facilities for five or fewer people also fall into this occupancy group. In many jurisdictions these occupancies are regulated under the International Residential Code (IRC) when it is adopted by the local jurisdiction. S 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Congregate living facilities with 16 or fewer nontransient occupants or 10 or fewer transient occupants are also classified as R-3 occupancies. Lodging houses are a defined term for facilities having one or more permanent occupants paying rent for guest rooms. • Permanent residency Care facilities for five or fewer persons are permitted to comply with the International Residential Code if an automatic sprinkler system is provided. Also, owner-occupied lodging houses with five or fewer guest rooms and 10 or fewer occupants are allowed to be constructed in accordance with the IRC if they meet the IRC’s height criteria of three stories or less. Taller R-3 occupancies must use the IBC. Lodging houses with more than five guest rooms are to be classified as R-1 for transient lodging and R-2 if used for nontransient use, but only if they exceed the 10 or 16 occupant load threshold. Otherwise, they are R-3s. • Group R-4 occupancies are used for residential care or assisted-living uses with more than 5 but not more than 16 occupants receiving custodial care, excluding staff. Under these conditions, Group R-4 is used in lieu of Group I. This occupancy group is to meet the requirements for R-3 occupancies except as otherwise provided for in other sections of the IBC. • 24-hour supervision • 24-hour supervision Group R-4, Condition 1 Group R-4, Condition 2 As for I-1 occupancies, there are two conditions related to the ability of residents to respond to instructions: Condition 1 (§ 310.5.1) occurs where persons receiving custodial care are capable of responding to an emergency situation to evacuate the building. Condition 2 (§ 310.5.2) includes buildings in which there are any persons receiving custodial care who require limited verbal or physical assistance while responding to an emergency situation to complete building evacuation. See the I-1 discussion for the impact of the conditions on building design. When in doubt, uses should be classified as Condition 2. USE AND OCCUPANCY / 31 OCCUPANCY GROUPS Storage Group S Storage for materials with quantities or characteristics not considered hazardous enough to be considered a Group H occupancy is classified as Group S. The two subdivisions are similar to the distinctions made for F occupancies: ModerateHazard S-1 occupancies and Low-Hazard S-2 occupancies. The lists of examples for each category are quite lengthy and detailed. When occupancies contain mixed groups of various products it can be quite difficult to determine which occupancy group to use. Careful consideration of projected uses for the facility and potential changes in use over time must be considered. It is useful to confer with the client and with the building official early in the design process to get concurrence on the proposed classification. As in the distinction between F-1 and F-2 occupancies, the distinction between S-1 and S-2 is that S-2 is used for the storage of noncombustible materials. Note that “self-service storage,” also known as “mini-storage” facilities, are called out to be classified as an “S-1” occupancy. This is due to the varied nature of materials that are often stored in such facilities and the likelihood of such materials being haphazardly and densely packed. Utility and Miscellaneous Group U This group is for incidental buildings of an accessory nature. These structures are typically unoccupied except for short times during a 24-hour period and are typically separate from and subservient to other uses. The code now classifies “greenhouses” that are not classified as another occupancy as a “U” occupancy. This occupancy group is used sparingly. It is not meant to be a catch-all for occupancy types that are not readily categorized. The AHJ has the ultimate responsibility for determination of occupancy classification using the criteria set forth in § 302.1. Note also that this group contains items that are not buildings, such as fences over 7' (2134) in height and retaining walls. 32 / BUILDING CODES ILLUSTRATED—THE BASICS • Aircraft hangars used for the storage and repair of aircraft are listed as S-1 occupancies. Factories for aircraft manufacture are included in the list for F-1 occupancies.