Class W buildings (a subset of Class S) are characterized by incombustible construction and light prefabricated structural members. They are not fire-resistant buildings. The exterior walls and roof coverings are prefabricated metal panels or sheet siding supported by an open-steel skeleton slant (modified A) frame. Ground floors are typically concrete slabs.
Included in this class are Uniform and Standard Building Code construction, Type IV (noncombustible), Basic Code Type V and ISO Class 3 buildings. This class is also referred to as Noncombustible.