Class D buildings are characterized by combustible construction. The exterior walls may be made up of closely spaced wood or steel studs as in the case of a typical frame house. Exterior covers may be wood siding, shingles, stucco, brick or stone veneer or some other type of material.
Floors and roofs are supported on wood or steel joists or trusses. The floor may be a concrete slab on the ground.
Construction Type V (wood-frame) of the Uniform, Type IV Basic and Type VI Standard Building Code are included in this class, as are ISO Class 1 buildings. This class is also referred to as Unprotected-protected One-hour Construction.