Construction Type

A building code classification system that categorizes buildings based on the fire resistance of their structural elements, determining allowable building height, area, and fire protection requirements.

What is Construction Type?

Construction type is a classification system in the building code that categorizes buildings based on the fire-resistance characteristics of their primary structural components — including the structural frame, bearing walls, floor construction, and roof construction. Along with occupancy classification, construction type is one of the two fundamental factors that determine a building's maximum allowable height and area.

The Five Types

The IBC defines five construction types, designated Type I through Type V: Type I (noncombustible, highest fire resistance — used for high-rises and large buildings), Type II (noncombustible with lower fire-resistance ratings), Type III (noncombustible exterior walls with interior wood framing), Type IV (heavy timber or mass timber), and Type V (wood-frame construction, the most common for smaller buildings). Each type has an A and B subclass based on the level of required fire-resistance ratings.

Impact on Building Design

Construction type directly affects what materials can be used, how tall and large a building can be, and what fire protection systems are required. A Type V-B wood-frame building is limited to relatively small heights and areas, while a Type I-A building with full fire-rated construction can be essentially unlimited in height and area (for most occupancies). Upgrading from one construction type to another can unlock significantly more buildable area but adds structural cost.

Construction Type and Project Feasibility

Choosing the optimal construction type is a key early design decision. Wood-frame (Type V) construction is typically the least expensive but most limited in height and area. Steel and concrete construction (Types I and II) allow larger buildings but at higher cost. The most cost-effective approach often involves maximizing the building size achievable within the least expensive construction type, using code provisions for height and area increases such as sprinkler bonuses and frontage increases.