803.15.1 Direct Attachment and Furred Construction
If the interior finish material is applied to furring strips, the intervening spaces between such furring strips shall comply with one of the following:
- Be filled with material that is inorganic or noncombustible.
- Be filled with material that meets the requirements of a Class A material in accordance with Section 803.1.1 or 803.1.2.
- Be fireblocked at not greater than 8 feet (2438 mm) in every direction in accordance with Section 718.
Exception: Compliance with Item 1, 2 or 3 is not required where the materials used to create the concealed space are noncombustible.