(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 requirements 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
Interior Finish Requirements Class
Occupancy Group Classification of the Space | Occupancy Group Designation | Exits and Shafts | Corridors b | Rooms More Than 1500 Sq. Ft. in Area a | Rooms Less Than 1500Sq. Ft. in Area a, d |
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 | Bd |
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 | De | De |
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.