Section 27-348. Interior finish

(a) Definition. For the purposes of this
  section, interior finish  shall  mean  those  materials  that  form  the
  exposed  interior surfaces of a building and that are part of or affixed
  to walls, fixed or folding partitions, ceilings, and other  construction
  elements.
    (b)  Classification.  Interior finish materials shall be classified in
  accordance with the surface flame-spread rating obtained  as  prescribed
  in the provisions of reference standard RS 5-5. Where an interior finish
  material is comprised of two or more materials laminated, glued, nailed,
  or otherwise secured together, the test rating for flame spread shall be
  based  upon  the composite of the materials in the form in which it will
  be used in construction. Interior finish materials shall be  grouped  in
  the  following  classes,  in  accordance with their surface flame spread
  characteristics:
 
            Interior Finish Class         Flame-Spread Rating
                      A                         0 to  25
                      B                        26 to  75
                      C                        76 to 225
                      D                        Over  225
 
    (c)  Requirements.  Interior  finishes  and  exposed   structural   or
  construction materials shall have a flame-spread rating not greater than
  that designated by the class prescribed for the various occupancy groups
  in  which  they  are  used,  as listed in table 5-4. Exceptions to these
  requirements are:
    (1) Finish flooring and floor coverings,  which  are  subject  to  the
  requrements of section 27-351.
    (2)  Wall  coverings  and  coatings  that are less than 0.036 in total
  thickness, when applied directly to a noncombustible, or  fire-retardant
  treated wood, substrate.
    (3) Exposed structural members and planking in buildings of class II-A
  construction,  which may be left exposed in any room or space, except in
  exits.
    (4) Twenty per cent (20%) of the aggregate wall and  ceiling  area  of
  any  room, space, or corridor required to have a class A or B rating may
  be finished with materials having a class C rating. This allowance shall
  include  the  area  of  doors,  folding  partitions,  windows,  glazing,
  skylights,   luminous   ceilings,  trim,  bases,  chair  rails,  panels,
  moldings, etc. This exception shall not operate as  a  waiver  of  other
  requirements of this code relating to opening protectives.
    (5)  When  a sprinkler system is provided in any room or space, and is
  installed in compliance with the construction provisions  of  subchapter
  seventeen  of  this  chapter, interior finish materials may be one class
  higher in flame-spread rating than required by tables 5-4.
    (d) Smoke density. No material shall be used for  interior  finish  in
  the  following  locations  if  the  material  develops  smoke in greater
  density than the rating shown, based upon a test conducted in accordance
  with the provisions of reference standard RS  5-5.  Materials  used  for
  interior finish that cover not more than twenty percent of the aggregate
  wall  and  ceiling  area of any room, space, or corridor shall be exempt
  from the above requirements.
 
       Location or Occupancy                   Smoke Developed Rating
 
       Exits, corridors ...............................   25
       Occupancy groups H-1 and H-2 ...................   50
       Rooms in which the net floor area

        per occupant is ten square feet,
        or less .......................................  100
 
    (e) Toxicity. No material shall be used in any interior location that,
  upon  exposure  to  fire  will  produce  products  of  decomposition  or
  combustion that are more toxic in  point  of  concentration  than  those
  given  off by wood or paper when decomposing or burning under comparable
  conditions.
    (f) Attachment of interior finish.
    (1) To be credited with the same  rating,  interior  finish  materials
  that  were  applied  to  a substrate when tested shall be applied at the
  building to an equivalent substrate.
    (2) Interior finish materials shall be cemented or  otherwise  secured
  in  place in the same manner and with materials equivalent to those used
  in flame-spread tests conducted in accordance with  subdivision  (b)  of
  this section for the applicable classification.
    (3)  Where walls, ceilings, partitions, or other construction elements
  are required to have a fire-resistance rating  or  are  required  to  be
  constructed  of  noncombustible  materials,  and  the interior finish is
  secured to studs or furring, the surface of the interior  finish  facing
  the concealed space shall either have a class A rating, shall be applied
  to  a  substrate  that has a class A rating, or shall have the concealed
  space completely filled with noncombustible material.
 
                   Table 5-4  Interior Finish Requirements
                                    Class
  ========================================================================
  Occupancy                                       Rooms More  Rooms Less
    Group        Occupancy    Exits                Than 1500   Than 1500
  Classification  Group       and                 Sq. Ft. in  Sq. Ft. in
  of the Space   Designation  Shafts Corridors{b}  Area{a}     Area{a,g}
  ________________________________________________________________________
  High Hazard      A             A        A             B            B
  Storage          B-1           A        A             B            C
  Storage          B-2           A        B             B{c}         C
  Mercantile       C             A        B             B{c}         C
  Industrial       D-1           A        A             B            C
  Industrial       D-2           A        B             B{c}         C
  Business         E             A        B             C            C
  Assembly         F-1a          A        B             B            B{d}
  Assembly         F-1b          A        B             B{c}         B{c,d}
  Assembly         F-2           A        B             B{c}         B{c,d}
  Assembly         F-3           A        B             B{c}         B{c,d}
  Assembly         F-4           A        B             B{c}         C
  Educational      G             A        A             B            C
  Institutional    H-1,H-2       A        A             B            B{d}
  Residential      J-1,J-2       A        A             B            B{f}
  Residential      J-3           B        D{e}          D{e}         D{e}
  ========================================================================
 
                             NOTES FOR TABLE 5-4
    a. In determining the applicable requirements for  rooms  or  enclosed
  spaces, the occupancy group classification of the room or enclosed space
  shall  be  the  governing  factor,  regardless  of  the  occupancy group
  classification of the building. For the purposes of this table, the area
  of  a  room  shall  be  that  floor  area  contained  within   enclosing
  construction   in  which  interior  doors  or  other  interior  openings
  represent not more than  ten  percent  of  the  area  of  the  enclosing

  construction.   Interior  doors  or  windows  that  are  constructed  of
  noncombustible materials and that are self-closing or automatic  may  be
  ignored  in  computing  door  or opening area. Rooms or spaces that have
  unprotected  openings  constituting more than ten percent of the area of
  enclosing construction shall not  be  considered  as  a  room.  Interior
  finish  requirements  for  rooms  are based upon rooms being enclosed in
  ceiling high partitions. Partitions,  to  be  considered  ceiling  high,
  shall  extend up to the floor or roof construction above or to a ceiling
  having at least a three-quarter hour fire-resistance rating.  Partitions
  that  do  not  comply  with  this requirement shall not be considered as
  enclosing the spaces, and the rooms or  spaces  on  both  sides  thereof
  shall be considered as one.
    b.  Rooms  or spaces through which it is necessary for occupants of an
  adjacent room to pass in order to reach the only  exit  shall,  for  the
  purposes  of  this  table,  be  considered  as  corridors. Where used in
  corridors, class B finish material shall not extend more than fifty feet
  between separations of class A finish material that  are  at  least  two
  feet wide.
    c.  On  the  street floor of one-story buildings in construction group
  II, ceilings, beams, trusses, etc. that  are  twenty  feet  or  more  in
  height from the floor to their lowest part, may have a class C finish.
    d.  Class  C  interior  finish  may  be  used in offices, or groups of
  offices, whose use is accessory to an occupancy, provided  such  offices
  are  separated from the occupancy, by construction having at least a two
  hour fire-resistance rating.
    e. Class C interior finish may be used in  the  residential  rooms  of
  one-  and two-story motels when there is a direct exit from each room to
  the exterior.
    f. Interior finish when used in the following spaces shall be at least
  class B:
    (1) Kitchens, cooking spaces, and pantries in buildings classified  in
  occupancy groups other than J-2 and J-3.
    (2) Repair and maintenance rooms.
    (3) Boiler rooms and incinerator combustion rooms.