314.6 Minimum Construction
Existing wood lath and plaster, existing 1/2-inch (12.7 mm) gypsum wallboard, existing installations of 1/2-inch thick (12.7 mm) wired glass which are or are rendered inoperative and fixed in a closed position, or other existing materials having similar fire-resistive capabilities shall be acceptable. All such assemblies shall be in good repair, free of any condition which would diminish their original fire-resistive characteristics.
Where 13/4-inch (44.5 mm) solid-bonded wood-core doors are specified in these regulations for existing high-rise buildings, new or existing 13/8-inch (34.9 mm) doors shall be acceptable where existing framing will not accommodate a 13/4-inch (44.5 mm) door.
Note: It is the intent of this provisions that existing wood frames may have their use continued.