Building Anatomy: Types and Classifications

Christopher J. Naum examines building types and classifications to anticipate variables in structural integrity and resiliency to the effects of extreme fire behavior for firefighters.


Today’s evolving fireground demands a greater understanding of buildings, occupancy risk profiling (ORP) and building anatomy by all companies operating on the fireground. The identification, assessment, probability, predictability and intrinsic characteristics of building performance under fire...


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Today’s evolving fireground demands a greater understanding of buildings, occupancy risk profiling (ORP) and building anatomy by all companies operating on the fireground. The identification, assessment, probability, predictability and intrinsic characteristics of building performance under fire conditions must not only be comprehended, but postulated into an adaptive fire-management model and flexible Incident Action Plan (IAP).

Building types and classifications are formulative toward anticipating variables in structural integrity and resiliency to the effects of extreme fire behavior, accelerated fire-load package growth rates and intensity levels during initial and sustained fire suppression. Understanding the construction and uses of a building is integral to effective and efficient firefighting operations and essential for all phases of combat fire engagement and suppression. Examining key insights into the manner in which buildings have been traditionally classified from a construction and code-compliance perspective will lead us to challenge today’s conventional wisdom.

NFPA 220: Standard on Types of Building Construction, 2012 edition, promulgated and published by the National Fire Protection Association (NFPA), defines standard types of building construction based on the combustibility and the fire-resistance rating of a building’s structural elements. Fire walls, non-bearing exterior walls, non-bearing interior partitions, fire barrier walls, shaft enclosures and openings in walls, partitions, floors and roofs are not related to the types of building construction and are regulated by other standards and codes, where appropriate.

 

Insights and history

• In 1952, the NFPA Committee on Building Construction secured tentative adoption of NFPA 220, Standard on Types of Building Construction, with subsequent revisions in 1954 and 1955. The definition of non-combustibility and editorial changes in the description of the fire resistance rating of structural members (under the definition of fire-resistive construction) were first adopted in 1956.

• In 1958, with the development of the use of plastics in building construction, recommendations on the types of standard fire tests to be used in evaluating the fire safety of these materials were first adopted.

• In 1975, a more fundamental definition of non-combustible was added, including the introduction of a definition of limited-combustible, based on potential heat value limitations and more generalized definitions for types of building construction.

• In 1979, the standard was extensively rewritten to introduce the nomenclature related to construction Type I through Type V, which included parenthetically placed hourly fire-resistance designations of the structural components.

Conventional building types

Buildings and structures are commonly classified according to their type of construction based on one of five basic types:

• Type I (or Type 1) – Commonly referred to as fire-resistive construction

• Type II (or Type 2) – Commonly referred to as non-combustible construction

• Type III (or Type 3) – Commonly referred to as ordinary construction

• Type IV (or Type 4) – Commonly referred to as heavy-timber construction

• Type V (or Type 5) – Commonly referred to as wood-frame construction

Variations include the use of the terms Class I, II, III, IV and V. Refer to NFPA 220, 2012 edition, Table 4.1.1 for additional insights and details related to fire-resistive ratings (hours) for exterior bearing walls, interior bearing walls, columns, beams, girders, trusses and arches, floor-ceiling assemblies, roof-ceiling assemblies, interior non-bearing walls and exterior non-bearing walls.

This system of designating types of construction also breaks down types of construction through the use of arabic numbers; e.g., Type I(442), Type II(111), Type III(200) – and indicate the fire-resistance rating requirements for certain structural elements:

1. First arabic number – Exterior bearing walls

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