What Is the Ideal Slope for a Garage Ramp?by Marc Gottlieb
When it comes to functional design for parking garage planning, architects have formulated a series of guidelines that dictate construction based on the specific usage of the facility. Retail garages are designed for daily miscellaneous visitors, whereas a facility hosting the same monthly visitors with assigned spaces calls for a different type of approach. However, these standard designs do not apply to every situation. Among the chief variables is the designated slope of the ramps, which is determined by a combination of factors.
Design the layout of the parking garage based on one of six "level of service" -- or LOS -- classifications, based on the intended use and location of the structure. The LOS designation, A to F, is determined based on the amount of anticipated traffic flowing in and out of the garage, and the familiarity of the facility by these users -- among many other classifying distinctions.
Plan the "wayfinding" concerns in the garage's design, which refer to the ease with which users can find their way in and around the structure. These considerations include the types of users in the garage, traffic patterns, visible signage, and driver and pedestrian access. The wayfinding determinations also dictate the type of security presence required for the garage.
Determine the ramp slope based on the requirements of the structure through LOS considerations and the expressed purpose of the garage. As a general rule of thumb, most floor-to-floor height requirements range from 10 to 12 feet. Minimums are limited to 8 feet 2 inches for van-accessible structures and 7 feet for standard parking entrances. A typical height of 10 feet generally requires a ramp slope grade of 5.56 percent. Every 4 inches of height over 10 feet requires an increase of the slope grade by roughly .18 to .19 percent. Increasing the height of clearance will affect the LOS designation, and this will extend to the slope grade percentage as well.
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