“the area within the inside perimeter of the exterior walls under consideration” and shall include the usable area under the horizontal projection of the roof or floor above” The 2018 codes incorporate some changes to address occupied roofs and to clarify their allowed uses. The first portion of the change is in Section 302.1 that clarifies that occupied roofs are required to be classified as an occupancy. In order to determine exiting requirements, floor loads, etc, you need to have an occupancy classification. Section 302.1 states:
“Occupied roofs shall be classified in the group that the occupancy most nearly resembles, according to the fire safety and relative hazard involved…”
The 2018 code also provides direction as to where the occupancies can be located. Section 503.1.4 states:
“A roof level or portion thereof shall be permitted to be used as an occupied roof provided the occupancy of the roof is an occupancy that is permitted by Table 504.4 for the story immediately below the roof. The area of the occupied roofs shall not be included in the building area as regulated by Section 508. And “Elements or structures enclosing the occupied roof areas shall not extend more than 48 inches above the surface of the occupied roof”.
This code would require that an occupied roof above a story only permitted for R occupancy be categorized as R occupancy. The second code section allows for landscaped areas or benches to be installed on the roof.
The 2015 IBC defines a high-rise building as:
“A building with an occupied floor located more than 75 feet above the lowest level of fire department vehicle access”
This defines a building being a high rise based on having an occupied floor above 75 feet.
Based on the definitions of a story and floor, an uncovered roof deck is not considered a story because there is no floor or roof above, and it is not considered a floor because it does not have exterior walls and is not under the projection of a roof or floor above. In addition, since the definition of a high rise also uses the term “occupied floor”, this also does not apply to a roof deck, and this building will not be considered a high rise as long as the floor below the high rise is under the criteria of 75 feet above the lowest level of fire department access.
Occupied roofs being used as a roof amenity are typically assembly type of use, and where above a floor that is R occupancy, they should therefore be categorized as A-type occupancy (versus R occupancy) for the purposes of determining exit travel distances, live loads, occupant load, accessibility, etc. Where, based on type of construction/height requirements, A occupancy is not allowed on the floor below the roof deck, and where the roof deck amenity is 75 feet above the lowest level of fire department access and is not designed as a high rise, additional requirements shall be as follows:
The occupant load of the roof deck amenity area will be limited to a maximum of 49 persons. Net floor area can be used. The occupant load factor shall be approved by the Building Official.
Exit paths can be excluded from the occupant load of the roof deck provided they are clearly defined as an exit path only.
Two means of egress will be required from the roof deck
Two exits will be provided from all occupied areas. An elevator will also be provided for ADA access and fire department emergency use (stretcher compatible).
No areas of the occupied roof deck will be enclosed, excluding required vestibules for elevators/stairs or mechanical uses.
At least one side of the occupied roof deck area shall be no higher than 75 feet above the elevation of the approved fire department access for the roof deck.
The occupied area of the roof deck shall be located on a level that is accessible from an approved fire department access point from the portion of the roof deck that is less than 75 feet above the fire department access.
Live loading for the roof amenity area and exit paths shall be a minimum of 100 psf.