2006 New York Code - Exterior Stairs.

 
    § 27-376 Exterior stairs. Exterior stairs may be used as exits in lieu
  of interior stairs provided they comply with all of the requirements for
  interior stairs, except enclosure, and except as modified below:
    (a)  Capacity.  The  capacity of exterior stairs shall be as listed in
  table 6-1.
    (b) Height limitation. No exterior  stair  shall  exceed  seventy-five
  feet or six stories in height.
    (c)  Construction.  Exterior  stairs  shall be constructed entirely of
  noncombustible  materials,  except  that  in  buildings  classified   in
  occupancy  groups  other  than  G,  F,  or  H, of construction group II,
  located outside the fire districts, exterior  stairs  may  be  built  of
  combustible  materials when the buildings are two stories or thirty feet
  in height or less and have an occupant load not exceeding forty  persons
  per  floor  above the street below. Exterior stairs shall be roofed, and
  shall be protected along their outer  sides  as  required  for  exterior
  corridors  in subdivision (f) of section 27-369 of this article. Treads,
  landings, and platforms shall be solid and unperforated. Risers  may  be
  partially open to permit water and snow to drain.
    (d)  Opening  protective.  In  buildings four stories or fifty feet in
  height or more, there  shall  be  no  openings  in  the  building  walls
  adjoining  exterior  stairs  other  than  one-quarter  hour self-closing
  swinging fire doors, and no openings nearer than ten feet to  the  stair
  (measured  horizontally)  that  are not provided with three-quarter hour
  opening protectives.
    (e) Location. No exterior stair shall be located nearer than ten  feet
  to an interior lot line.
    (f) Discharge. Exterior stairs shall extend continuously to grade.