Construction Type
The IBC's five ways of classifying a building's structure by fire performance.
Quick Answer
Construction type is the IBC classification of a building into Types I through V based on whether its structural elements are noncombustible or combustible and how many hours of fire resistance they must provide. Type I is the most fire-resistant and Type V the least. The type limits allowable height and area.
The Full Picture
Construction type describes how a building is built, not what it is used for. IBC Chapter 6 defines five types. Type I and Type II use noncombustible materials, Type III has noncombustible exterior walls with combustible interior elements, Type IV is heavy timber and, in recent editions, mass timber, and Type V allows combustible materials throughout.
Types I, II, III, and V are further divided into subtypes, commonly A and B. The A subtype requires the structural elements to carry fire-resistance ratings, while the B subtype generally requires little or no rating for most elements. The required ratings for structural frame, bearing walls, floors, and roofs are listed in a table in Chapter 6, expressed in hours.
The type matters because it works with occupancy classification to set how tall and how large a building can be. A more fire-resistant type permits more height and floor area, which is why large high-rise towers are generally Type I while many low-rise wood-frame apartment buildings are Type V. Fire sprinklers and other features can allow additional height and area within the limits of the code.
Construction type is a significant cost and design driver. Choosing a more protected type can add cost through fire-rated assemblies and fireproofing, while choosing a less protected type may cap the building's size. Recent IBC editions have added mass timber subtypes within Type IV, reflecting growing use of engineered wood for taller buildings.
Real Examples
Common Misconceptions
People assume: Construction type means the same thing as fire-resistance rating of walls.
Actually: Construction type is a whole-building classification. Individual fire-resistance ratings are separate requirements for specific elements, though the type sets the minimum ratings for the structural frame and floors.
People assume: Type V construction is unsafe or low quality.
Actually: Type V is a code classification that permits combustible materials. Buildings of this type are code-compliant and are typically sprinklered, but they are subject to tighter height and area limits.
Does MeltPlan Solve This?
Partially — adjacentMeltPlan Code can help teams look up the IBC construction type provisions and see how the chosen type interacts with occupancy, height, and area limits. Selecting the construction type is a design decision made by the architect and engineer, and MeltPlan does not design or specify the structure.
Look up construction type requirements →Frequently Asked Questions
What are the IBC construction types?
There are five: Type I and II (noncombustible), Type III (noncombustible exterior walls with combustible interior), Type IV (heavy timber and mass timber), and Type V (combustible). Most have A and B subtypes.
What is the difference between Type A and Type B construction?
In general, subtype A requires structural elements to have fire-resistance ratings and subtype B requires little or none. The exact ratings are listed by element in the IBC's construction type table.
Does construction type affect building cost?
Yes. More protected types require fire-rated assemblies and fireproofing, which can add cost, while less protected types can limit building height and area. The cost impact depends on the project and market.
Where is construction type defined in the IBC?
Chapter 6, Types of Construction, defines the types and the required fire-resistance ratings. Chapter 5 then ties type and occupancy to allowable height and area.