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32A-144 IEBC section 912.4Table 912.4 Means of Egress Hazard Categories R-2 use level 3; B use level 4 912.4.1 Means of egress for change to higher hazard category. When a change of occupancy classification is made to a higher hazard category (lower number) as shown in Table 912.4, the means of egress shall comply with the requirements of Chapter 10 of the International Building Code. Exceptions: 1. Stairways shall be enclosed in compliance with the applicable provisions of Section 803.1. 2. Existing stairways including handrails and guards complying with the requirements of Chapter 8 shall be permitted for continued use subject to approval of the code official. 3. Any stairway replacing an existing stairway within a space where the pitch or slope cannot be reduced because of existing construction shall not be required to comply with the maximum riser height and minimum tread depth requirements. 4. Existing corridor walls constructed on both sides of wood lath and plaster in good condition or 1/2-inch-thick (12.7 mm) gypsum wallboard shall be permitted. Such walls shall either terminate at the underside of a ceiling of equivalent construction or extend to the underside of the floor or roof next above. 5. Existing corridor doorways, transoms and other corridor openings shall comply with the requirements in Sections 705.5.1, 705.5.2 and 705.5.3. 6. Existing dead-end corridors shall comply with the requirements in Section 705.6. 7. An existing operable window with clear opening area no less than 4 square feet (0.38 m2) and minimum opening height and width of 22 inches (559 mm) and 20 inches (508 mm), respectively, shall be accepted as an emergency escape and rescue opening. IEBC COMMENTARY The basic premise here is for the means of egress requirements to be the same as required for new construction when the change of occupancy classification is to a higher (lower number) classification. The exceptions relate to common problem areas where it is practical to fully comply with requirements for new construction. Exception 1 allows the same provision for the limited enclosures of stairways as allowed for Level 3 alterations. Exception 2 allows handrails and guards to meet the limited requirements of Chapter 8. The reader will note that Chapter 8 contains no specific requirements for guards and handrails. However, it must be remembered that the provisions of Chapter 7 also apply to Chapter 8; therefore, the provisions of Sections 705.9 and 705.10 are applicable. Exceptions 3 through 7 give allowances for construction commonly found in existing construction that make full compliance with the present IBC impractical. SECTION 1021 NUMBER OF EXITS AND CONTINUITY TABLE 1021.1 MINIMUM NUMBER OF EXITS FOR OCCUPANT LOAD OCCUPANT LOAD (persons per story) MINIMUM NUMBER OF EXITS (per story) 1-500 2 501-1,000 3 More than 1,000 4 1021.1 Exits from stories. All spaces within each story shall have access to the minimum number of approved independent exits as specified in Table 1021.1 based on the occupant load of the story. For the purposes of this chapter, occupied roofs shall be provided with exits as required for stories. Exceptions: 1. As modified by Section 403.5.2. 2. As modified by Section 1021.2. 3. Exit access stairways and ramps that comply with Exception 3 or 4 of Section 1016.1 shall be permitted to provide the minimum number of approved independent exits required by Table 1021.1 on each story. 4. In Group R-2 and R-3 occupancies, one means of egress is permitted within and from individual dwelling units with a maximum occupant load of 20 where the dwelling unit is equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1 or 903.3.1.2. 5. Within a story, rooms and spaces complying with Section 1015.1 with exits that discharge directly to the exterior at the level of exit discharge, are permitted to have one exit. This section requires every floor of a building to be served by at least two exits (see Figure 1021.1). Similarly, every portion of a floor must also be provided with access to at least two exits. Where more than 500 occupants are located on a single floor, additional exits must be provided. For example, if a floor has an occupant load of 750, each occupant of that floor must have access to not less than three exits (see Table 1021.1). This section also addresses the need for exits from roofs that are occupied by the public, such as rooftop decks or dining areas. It is important that exit enclosures serve the roof level in addition to the other floor levels. The text references buildings and spaces with one means of egress (see Sections 1021.2 and 1015.1). Where a building requires more than one exit, that number, determined in accordance with Table 1021.1, is required from each floor level. This is true even if an individual floor level qualifies as a space with one means of egress in accordance with Table 1015.1. Table 1015.1 is intended to be applicable to rooms and spaces, but not to entire floor levels. One of the main concerns has been that vertical travel takes longer than horizontal travel in emergency exiting situations. However, if the single exit space can exit directly to the exterior rather than into an interior corridor, this provides a higher level of safety. This is the reasoning behind Exception 5. While the term “building” limits the area addressed to that bordered by exterior walls or fire walls, a common application of Exception 5 is on a tenant-by-tenant basis. For example, a strip mall may not meet the provisions for a building with one means of egress. However, assume a tenant meets the provisions for a space with one means of egress in accordance with Section 1015.1. This tenant could exist as either a stand-alone single-exit building or a single-exit tenant space that exits into an interior corridor. Is it not as safe to permit this tenant to exist as part of a larger building with the door exiting directly to the exterior? While not specifically stated in this section, there is a situation where the single means of egress can be used from a multilevel space. Section 505 permits mezzanines to be considered part of the floor below for purposes of means of egress. When a mezzanine meets the occupant load in Table 1015.1 and the common path of travel distance (see Section 1014.3) measured from the most remote point to the bottom of the stairway, it can be considered a space with one means of egress. Exception 4 is based on multiple years of practice within an individual dwelling or sleeping unit. In Group R-2 and R-3 buildings with multistory dwelling or sleeping units, the means of egress from a dwelling or sleeping unit is typically permitted to be from one level only. In a Group R-2 apartment or townhouse-style building, if the unit has an occupant load of 20 or less, the building is sprinklered with an NFPA13 or 13R system and the common path of travel from the most remote point on any level to the exit door from the unit itself is 125 feet (22 860 mm) maximum (see Section 1014.3, Exception 4), that unit may have only one means of egress. However, once the occupants exit the unit itself, they must be outside or the floor level must have access to two or more means of egress for all tenants, depending on the number required for the building as a whole. While this exception also lists Group R-3, Section 1021.2 says all Group R- 3 dwellings can have one exit regardless of occupant load or type of sprinkler system. Common path of travel is not applicable in single-exit buildings. The emergency escape and rescue opening addressed in Section 1029 does not count towards the required number of exits. Exception 3 is to allow for open exit access stairways, as permitted in Section 1016.1, Exceptions 3 and 4, to count towards the required number of exits for that upper or lower level floor or space. For example, Section 1016.1, Exception 4 allows for a two-story office building to use two open exit access stairways provided that exit access travel distance includes travel down the stairway and to the exit door. This exception allows the two exit access stairways to meet the two-exit requirement in Table 1021.1 for that second level. Exception 2 allows for the single-exit buildings in Section 1021.2. The high-rise provisions in Section 403.5.2 have a requirement for an additional stairway in buildings 420 feet (128 m) or taller. Exception 1 is in recognition of that additional requirement. Table 1021.1 specifies that the minimum number of exits available to each occupant of a floor is based on the total occupant load of that floor. This is so that at least one exit will be available in case of a fire emergency and to provide increased assurance that a larger number of occupants can be accommodated by the remaining exits when one exit is not available. While an equal distribution of exit capacity among all of the exits is not required, a proper design would not only balance capacity with the occupant load distribution, but also consider a reasoned distribution of capacity to avoid a severe dependence on one exit. Buildings with one exit are permitted where the configuration and occupancy meet certain characteristics so as not to present an unacceptable fire risk to the occupants. Buildings that are relatively small in size have a shorter travel distance and fewer occupants; thus, having access to a single exit does not significantly compromise the safety of the occupants since they will also be alerted to and get away from the fire more quickly. It is important to note that the provisions in Section 1021.2 apply to individual stories. Multiple single-exit spaces may exist in the same building, including those cases where differing occupancies exist. Therefore, Table 1021.2 can address mixed occupancy buildings. Occupants of a story of limited size and configuration may have access to a single exit, provided that the building does not have more than one level below the first story above the grade plane. The limitation on the number of levels below the first story is intended to limit the vertical travel an occupant must accomplish to reach the exit discharge in a single-exit building. Taken to its extreme, the code would otherwise allow a single exit in a building with one or two stories above grade and an unlimited number of stories below grade. This would be clearly inadequate for those stories below grade. Only one exit is required from a story where permitted by Table 1021.2 regardless of the number of exits required from other stories in the building. For example, a Group B occupancy on the second floor of a multistory building is only required to have one exit from the story provided its occupant load does not exceed 29 and the maximum travel distance to an exit does not exceed 75 feet (22 860 mm). The number of occupants and travel distances on the other stories do not affect the determination of the second story as a single-exit story. Other stories are also regulated independently as to number of exits. Where multiple tenants or occupancies are located on a specific story, they are to be regulated independently for single-exit determination. The provisions can be applied to specific portions of the story, rather than the story as a whole. As an example, the second story of a building houses two office tenants, each with their own independent means of egress. Each tenant would be permitted a single, but separate, exit provided each had an occupant load of less than 30 and a travel distance not exceeding 75 feet (22 860 mm). This portion-by-portion philosophy also applies to a mixed occupancy condition provided each of the individual occupancies does not exceed the limitations of Table 1021.2 (see Figure 1021.2). Group R-3 building occupancies are permitted to have a single exit since they do not have more than two dwelling units (see Section 310). Table 1021.2 (see separate sheet) Table 1021.2 lists the characteristics a building must have to be of single-exit construction, including occupancy, maximum height of building above grade plane, maximum occupants or dwelling units per floor and exit access travel distance per floor. The occupant load of each floor is determined in accordance with the provisions of Section 1004.1. The exit access travel distance is measured along the natural and unobstructed path to the exit, as described in Section 1016.1. If the occupant load is exceeded, as indicated in Table 1021.2, two exits are required from each floor in the building. Likewise, if the travel distance or number of dwelling units is exceeded, as indicated in Table 1021.2, two exits are required from each floor of the building. The exit enclosure required in a two-story, single-exit building is identical to any other complying exit (i.e., interior stairs, exterior stairs, etc.). Similarly, the fire-resistance rating required for opening protectives is identical to that required by Section 715. Notes a and b are in reference to unique exit criteria for parking structures and air traffic control towers. Notes c and d provide for increased travel distance for Groups R-2, F, S and B with certain limitations.