ramp slopes for parking ramp design

huangyhg

ramp slopes for parking ramp design
we are working on a retrofit of an existing building.  does any one know of rules of thumb as it relates to reasonable slopes for ramps in a parking garages.  the parking will be heated and totally enclosed so ice will not be a problem except at the entrance and exit.
i am working on a project now that is using an 18% slope (very high).   the architect set this slope based off of building constraints and required "approach" slopes so the vehicles didn't bottom out.  some guidelines can be found in the architectural graphic standards book.