Chapter 26: Plastic, California Building Code 2016 …
In nonsprinklered buildings, foam plastic having a thickness that does not exceed 4 inches (102 mm) and a maximum flame spread index of 75 is permitted in walk-in coolers or freezer units where the aggregate floor area does not exceed 400 square feet (37 m 2) and the foam plastic is covered by a metal facing not less than 0.032-inch-thick (0.81 ...