Section 147. Bulkheads and scuttles

1. Except as otherwise provided in
  subdivision two of this section, every required  stair,  fire-stair  and
  fire-tower  in  dwellings  three  stories or more in height shall have a
  bulkhead constructed as provided for fireproof dwellings in section  one
  hundred  four,  except  that the bulkhead of any required stair which is
  not required to be fireproof may be built of wood covered on the outside
  with twenty-six gauge metal and on the inside with wire  or  metal  lath
  covered  with  two  coats  of  cement  plaster  or  other fire-retarding
  material approved by the department.
    2. Such a dwelling which is two stories or less in height, or is three
  stories  in  height  and  erected  pursuant  to  plans  filed  with  the
  department  on  or  after  May  first,  nineteen  hundred fifty-nine and
  occupied by not more than one family on each story, shall be provided at
  each required  stair,  fire-stair  or  fire-tower  either  with  such  a
  bulkhead  or  with  a  scuttle  at least two feet by three feet in size,
  located in the ceiling of the public  hall  on  the  top  story  and  so
  arranged  as  to  provide  direct  and uninterrupted access to the roof.
  Every such scuttle shall be arranged to  be  readily  opened,  shall  be
  covered on the outside with metal and shall be provided with stairs or a
  stationary  iron ladder or ladders leading thereto and easily accessible
  to all the tenants of the dwelling.
    3. No bulkhead or other superstructure on the roof shall be  used  for
  human occupancy.
    4. When a dwelling has a pitched or sloping roof with a pitch or slope
  of  more than fifteen degrees, no bulkhead or scuttle or stair or ladder
  leading thereto shall be required.