Modified Fire Resistive Construction

• buildings with exterior walls, floors, and roofs of masonry materials described in the definition of fire resistive (Construction Class 6) — less thick than required for fire-resistive structures but not less than four inches thick, or
• fire-resistive materials with a fire-resistance rating less than two hours but not less than one hour

The exterior bearing walls and load-bearing portions of exterior walls must be of noncombustible materials or of masonry, but exterior nonbearing walls and wall panels may be slow-burning, combustible, or with no fire- resistance rating.

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Poured gypsum roof with one-hour fire-resistance rating

Wall, floor, and roof assembly with noncombustible
panels, with one-hour fire-resistance rating