Section 27-458. Ramps

Vehicular ramps in public garages shall not exceed a
  gradient of one in seven, and their surfaces shall be nonslip. A landing
  having a minimum  length  of  twenty  feet  shall  be  provided  at  the
  discharge  point  at  the  street  level,  within the street line. Ramps
  serving as required exits shall be enclosed in construction having a two
  hour fire-resistance rating except that openings for motor  vehicles  at
  each  parking  tier  may  be  protected by a water curtain consisting of
  deluge-type sprinkler heads supplying at least three  gallons  of  water
  per minute per linear foot of opening.