DEPARTMENT OF DEVELOPMENT SERVICES BUILDING DIVISION. Ronald L. Lynn, Director/Building Official Gregory J. Franklin, Assistant Director Neil Burning, Manager of Plans Examination. PROPOSED ASSEMBLY USES IN EXISTING OPEN PARKING GARAGES.
DEPARTMENT OF DEVELOPMENT SERVICESBUILDING DIVISION
Ronald L. Lynn, Director/Building Official
Gregory J. Franklin, Assistant Director
Neil Burning, Manager of Plans Examination
The Clark County Building Division has identified a number of concerns regarding the proposed use of an existing open parking garage for any assembly uses.
Mandalay Bay Concert
Fremont Street Concert
The Building Code requires a parking garage to meet a minimum structural design standard of 40 psf for live loads, whereas the minimum live load design standard for buildings used for assembly purposes is 100 psf, or 250% greater.
If a stage or platform is provided in the assembly use, the minimum live load required for the stage or platform is 125 psf or 313% greater than what is required for parking garages.
All buildings must also meet specific occupancy category requirements for structural design. These categories are assigned by the intended use of the building. A parking garage is assigned as a Category II building, while a building used for public assembly is classified as a Category III building.
A Category III classification requires the building to meet more stringent design standards for resisting seismic, snow and wind loads. Therefore, the minimum structural design for buildings used for an assembly use must resist a 25% greater seismic load, a 10% greater snow load, and a 15% greater wind load than what is required for the structural design of a parking garage.
These significant differences in minimum structural design requirements represents a potential life-safety risk to the building occupants, if an existing parking garage was allowed to be used for assembly purposes.
There are also substantial differences in the means of egress requirements for buildings used for assembly versus a building used as an open garage, including the following:
In a typical parking garage (non-sprinkled) the occupants are permitted to travel a distance of 300 feet in order to reach an exit.
However, a building used for public assembly is limited to a maximum travel distance of 200 feet; 250 feet if the building has fire sprinklers throughout.
This travel distance restriction is due to the fact that it takes much more time for the occupants in assembly buildings to exit due to the much greater number and density of the occupants.
Size and Number of Exits
The occupant load for a parking garage is required to be based on an occupant load factor of 200 gross square feet per person.
In contrast, the required occupant load factor for a building used for public assembly is 15 net square feet per person.
This means the number of occupants in buildings used for public assembly is approximately thirteen (13) times greater than a typical open parking garage having the same floor area.
Also, due to the much larger number of occupants, many more exits are required to allow the occupants to safely evacuate the assembly building.
Capacity (Width) of Exit Stairs
Since buildings used for assembly have thirteen (13) times the number of occupants than a parking garage, the dimensional size or widths of the exit stairs must also be much greater than those used in parking garages.
Exit Stair Enclosures
All stairs serving a building used for public assembly are required to be enclosed within two (2)-hour fire-resistant-rated shaft enclosures. In contrast, stairways that serve an open parking garage are allowed to be unprotected and completely open.
A building used as a parking garage is allowed a clear ceiling height of only 7 feet in the vehicle and pedestrian traffic areas.
A building used for public assembly must maintain a minimum ceiling height of 7 feet 6 inches.
Automatic fire sprinkler systems are not required to be installed in open parking garages, regardless of the height or area of the garage.
However, the Building Code requires an automatic fire sprinkler system to be installed throughout a building used for assembly, if the building exceeds 5,000 square feet in area or if the number of occupants exceeds 300 people.
Sprinklers are always required if the assembly use is located on an elevated floor level or within a basement not having direct access to the exterior of the building.
Fire alarms and other fire alarm/occupant notification systems are not required for open parking garages.
However, a fire alarm system is required for any building used for public assembly, if the number of occupants exceeds 300. If the number of occupants exceeds 1,000, then the building would also be required to have an emergency voice/alarm communication system installed throughout.
A minimum number of plumbing fixtures such as water closets, lavatories, drinking fountains, and service sinks, is not required for open parking garages. However, the Building Code requires a large number of plumbing fixtures in buildings used for assembly due to the extremely large number of building occupants.
Handicap accessibility requirements of the Building Code must also be met for any building used for public assembly.
These requirements include an accessible means of egress, accessible routes throughout the building, accessible entrances, accessible bathroom facilities, accessible drinking fountains and unisex toilets and bathing rooms.
There are significant differences between the accessible means of egress requirements for an assembly use and those required for an open parking garage.
Areas of refuge are not required at exit stairways or elevators serving open parking garages.
Buildings used for assembly must have an accessible means of egress. This requires that the exit stairways contain an area of refuge (an enlarged floor-level landing).
Similarly, to be considered part of an accessible means of egress, an elevator must be accessed from either an area of refuge or from a horizontal exit.
Enclosed elevator lobbies are not required for elevators serving open parking garages.
However, if an assembly use is added to an existing open parking garage, then the elevator is required to be enclosed in a fire-resistance rated shaft enclosure and if the elevator shaft connects more than three stories, then an enclosed elevator lobby would be required at each floor.
There are special electrical, mechanical and plumbing design requirements for any building used for public assembly.
The most significant requirements are for the required smoke control systems and for emergency and standby power. These emergency power systems are necessary to ensure the smoke control systems work if the building should lose power and also to have sufficient lighting to allow the occupants to exit the building.
The Building Code does contain “special provisions” for new buildings designed for mixed uses; such as buildings having separate areas within the same building to be used for both an open parking garage and for assembly.
These “special provisions” are subject to specific conditions. There are two different design approaches as to how the mixed-occupancies are to be separated:
Under this design approach, fire-resistance rated separations are not required between the different uses (occupancies).
Each occupancy in the building is individually classified and code requirements are applicable to each portion of the building based on the occupancy classification of that space; however, the most restrictive applicable provisions Section 403 (high-rise requirements) and Chapter 9 (fire protection systems) must be used for the entire building.
Further, the allowable height and area of the building must be based on the most restrictive allowances of the occupancy groups under consideration.
IBC Section 508.3.3 – Separated Occupancies
Under this design approach, each occupancy in the building is individually classified, and the individual occupancies must be separated from the adjacent occupancies by fire-resistance rated walls/floors in accordance with the Building Code. Each fire area then must comply with the applicable code requirements based on the occupancy classification of that portion of the building.
The Clark County Building Division has significant concerns regarding the potential risks to the life safety and welfare of the building occupants, if a parking garage building is not brought into full compliance with all current code requirements for buildings used for public assembly.