62 – Key Space.

§ 62. Key  space.  All  ceilings,  stud partitions and furred walls in
  tenements, apartments, hospitals, schools, and  other  public  buildings
  where  plastered  with  lime  on  wood  lath  shall  have  not less than
  three-eighths space between lath. All grounds and jambs shall  mean  not
  less than seven-eighths from the stud.