The Basement Parking space type refers to parking located below grade within an occupied building. As defined for the WBDG, the Level of Service (LOS) (refer to Architectural Graphic Standards, 10th Edition, page 106) of the Inside/Basement Parking is LOS B, indicating use by some unfamiliar users, moderate daily turnover, and medium percentage of small cars and light trucks; and requiring one-way aisles of 11'-0" straight-ways and 13'- 6" turns. See also WBDG Parking Structure.
First and foremost, parking structures—either basement, structured, or surface—must provide for the safe and efficient passage of automobiles as well as visitors to and from their vehicles. Therefore, attention should be given to providing the maximum driver visibility possible at all turning points along the roadway. While federal courthouses have Inside/Basement parking for only the judges and Marshals Service, it is typical beneath office buildings for building occupants and visitors as well. Characteristics and features that distinguish the Basement Parking space type include:
- Additional Structural Requirements: Below grade extension of the building structure to accommodate basement parking is required. This involves additional excavation, structural frame, floor slabs above, sloped vehicle access ramps, and basement perimeter walls and partitions separating parking from other building enclosed areas. Typical structural floor construction is 4000 PSI 6" concrete slab with welded wire fabric designed for a live load of 80 LBS/SF, and with a ramp slope of no more than 5.5%.
- Signage and Wayfinding: Signage should indicate all major internal pedestrian access points as well as external major roads and buildings. In basement parking, pavement markings are reflective paint and traffic control signage is usually reflective metal with minimum 5" high letters. The Manual on Uniform Traffic Control Devices for Streets and Highways (ANSI D 6.1e) provides guidance on pavement marking and signage.
- Ventilation: The parking area is generally supplied with unconditioned air utilizing multiple speed fans, preferably interlocked with carbon monoxide detectors tied into an alarm system. 1-1/2 CFM per square foot capacity and 100% exhaust air coordinated with the supply air system is recommended.
- Parking Management: Usually pre-manufactured booths with transaction windows and deal trays are installed at vehicular entrances/exits to manage entering and exiting vehicles. A cooling system, like a packaged terminal air conditioner (PTAC), is usually incorporated to supply the booth with outside air at a positive pressure relative to surrounding parking areas.
- Security Protection: Beyond parking management, several security measures are incorporated into typical basement parking spaces to ensure the security of visitors. These generally include: uniform lighting coverage, preferably with energy- efficient light fixtures; closed circuit television (CCTV) cameras; card reader access control for vehicle entrance doors; concrete filled protective bollards to protect vehicle entry keypads; and hydraulic lift wedge type barriers for egress control. Also critical is security control of access from the parking area to other occupied areas of the building either through termination at a security screening in the main lobby or through access control at the elevator or stair entrance. Elevator lobbies are usually tempered safety glass panels with glazed exterior doors containing keyed lever lockset with panic release bar. See also WBDG Safe—Security for Building Occupants and Assets.
- Fire and Life Safety: Proper notification systems, lighting, and signage are required to facilitate safe and speedy evacuations during an emergency in the basement parking spaces. This is usually accomplished with proper fire alarm wiring, pull stations, strobes, annunciators, and exit signage. In addition, exposed pipe sprinkler system is extended into the basement parking, with a hose bib at every level. See also WBDG Safe—Fire Protection.
- Drainage and Storm Water Management: Water runoff from vehicles is typically dealt with in basement parking spaces by installing trench drains with cast iron covers at all vehicle entrance/exit points, sand and oil traps at all storm drain discharge points, and floor area drains at every low point.
The following is representative of a plan of a basement garage located in a high-rise office building.
Relevant Codes and Standards
Educational Facilities, Federal Courthouse, Health Care Facilities, Libraries, Office Building, Parking Facilities, Research Facilities
Structured Parking, Surface Parking
Secure / Safe—Fire Protection, Secure / Safe—Security for Building Occupants and Assets