Design for Code Acceptance (DCA) #1 Flame Spread Performance of Wood Products provides building code accepted flame spread ratings for various wood products and species which are normally used as interior finishes for walls, ceilings, and floors in buildings.
Wood materials may be used as interior finish in almost all occupancies. IBC Table 803.9 indicates the finish classification required for every occupancy and location within the building. The required classifications (A, B, or C) are ranges of flame spread resulting from testing per ASTM E84 or UL723.
Flame spread classification is usually obtained from the manufacturer, but code officials and designers can also make use of DCA 1 to quickly determine the flame spread of lumber and various engineered wood products. Most wood species qualify as Class C, but some can qualify as Class B. All the products listed in DCA 1 also meet the maximum smoke-developed index of 450 required by the building code (803.1.1).
The flame spread index of fire retardant treated wood is required to be 25 or less (Class A) per Section 2303.2. Traditional wood floor covering is exempt from interior finish requirements, and exposed portions of Type IV (Heavy Timber) structural members are also exempt from the interior finish requirements of the code (Section 804).