Building codes & construction
Construction type (I–V)
CBC Chapter 6 classes I–V rank structures by material combustibility and fire resistance; with occupancy and sprinklers they cap a building's height and area.
Definition
Chapter 6 of the California Building Code sorts every building into construction Types I through V by how combustible and fire-resistant its structure is: Types I and II are noncombustible (concrete, steel), Type III pairs noncombustible exterior walls with wood interiors, Type IV is heavy and mass timber (including the tall mass-timber subtypes IV-A, IV-B and IV-C), and Type V permits any code-allowed material — in practice, light wood framing. Most types split into A (fire-protected) and B (unprotected) variants. Together with occupancy group and sprinkler system, the construction type sets a building's allowable stories, height and floor area.
Why it matters in an underwrite
Type selection is the biggest structural-cost fork in a multifamily budget: wood-frame Type V is the cheapest per square foot, Type III buys one more story for a modest premium, and Type I concrete or steel costs dramatically more. The jump usually happens because the unit count needs stories the cheaper type can't legally reach — so the right order is unit count, required type, then cost, not the reverse.
Sources & related guides
See also
See the term in the law itself
Read the controlling text in the Code Library, or ask the AI how it applies to your project.
Last reviewed 2026-07-29. General information, not legal advice.