The best design of a parking facility depends first and foremost on a number of factors including user, location, local codes, building size, functional layout, etc. However, there are typical design standards common in many parking garage designs. The following are some useful standards that may help answer some of your most common questions:
Parking Space Size
The size of parking spaces allowed is mandated by the local zoning or land development ordinances. For example, in Philadelphia commercial districts, the minimum size parking space allowed is 8’6” x 18’0”.
The size for parking stalls should be based on typical use. A general rule for this is: the lower the turnover, or the more urban a location is, the smaller the spaces can be tolerated by users. On the other hand, areas with high turnover, and which are less urban, will generally have larger spaces. However, variances of design wavers are often sought for parking stall dimensions.
Vehicle width vs. Parking Stall Width
A car door opening clearance is approximately 20 to 24 inches. Therefore, a good approach is to provide an extra foot of stall width when a space is up against a wall.
Vertical circulation for ramps
Ramp slopes with parking generally range from 5% to 6.67% maximum (per code). Further, speed ramp slopes range from 6.67% to 16 %.
Considering vertical circulation of floor to floor heights, these typically range from 10’0” to 12’0”. According to code, minimum required clearances are 8’2” for van accessible parking, and 7’0” for regular and other accessible spaces. In multilevel parking structures, van accessible parking spaces are permitted on one level.
Garage footprint dimensions
The minimum dimensions for a garage footprint consist of two structural bays. Two 60 ft. parking modules (2 way, 90 degree parking) would result in a width of 123’. On the other hand, two one-way bays with angled parking would be slightly less wide. However, additional width would increase in increments of the parking module.
The minimum garage length consists of the ramp, plus the end turning bays at each end of the garages. For a garage with two-way traffic there must be 180 ft. of ramp, two end bays of 28 ft., and two spandrel widths of 1 ft. For improved efficiency, the garage with two way traffic with end bay parking must have 180 ft. of ram, two end bays of 45 ft., and two spandrel widths of one ft. However, minimum garage length can be reduced by having the ramp rise only half of a level, instead of a full one.
A single helix (two-way) arrangement should be limited to five or six levels because of the number of turns required to pass all parking spaces. However, for a double threaded helix (one-way), arrangements allow for a vehicle to circulate up and then back down without making a U-turn at the top. In this case, a crossover should be provided at ramp mid-points to allow vehicles to switch from upward to downward to shorten the distance needed to exit.
Accessible spaces are a minimum of 8’-0” wide with a minimum 5’-0” wide access aisle. Two adjacent spaces may share the 5’-0” aisle. Van accessible spaces are minimum 8’-0” wide with a minimum of 8’-0” wide access aisle.
Accessible parking spaces should always be located in the most convenient location for the user traveling to their final point of destination. Further, when possible, accessible spaces should always be located in covered areas.