ISO Classes

ISO 1 – Frame

A building where the exterior walls, bearing walls and partitions, and the structural floors and roof, and their supports, are wood or light-gauge metal. This includes buildings where the wood or light-gauge metal has been combined with other materials to form composite components such as wood or metal studs with brick or stone veneer, stucco or metal siding. Buildings classified a ISO Class 1 are characteristic of this type.

  ISO 2 – Joisted Masonry

A building that has the exterior walls constructed of a material such as brick, hollow or solid concrete block, concrete, gypsum block, clay tile, stone, or similar materials. The structural floors and roof are of wood or light-gauge metal. Buildings classified as ISO Class 2 are characteristic of this type.

ISO 3 – Noncombustible

A building that employs a system of pre-engineered rigid steel framing members. The exterior walls are of metal siding, sandwich panels, or masonry, and the roof is clad with metal roofing or sandwich panels. Buildings classified as ISO Class 3 are characteristic of this type.  Due to the repetitive characteristics of pre-engineered metal buildings, it is advisable to reduce the 7% architectural fees included in the base costs.

ISO 4 – Masonry Noncombustible

A building where the structural floors and roof are of unprotected non-combustible materials such as metal decking or concrete on metal decking, and are supported by an unprotected structural steel frame, fire resistive exterior walls, or a combination of both. Buildings classified as ISO Class 4 are characteristic of this type.

ISO 5 – Protected Steel Frame / Modified Fire Resistive

A building where the structural floors and roof, and their supports are of non-combustible construction with a fire rating of not less than one hour. A building very similar to Construction Type D - Steel Frame; however, in Type E the non-combustible floor, roof, and framing components are protected with sprayed-fiber fireproofing. Buildings classified as ISO Class 5 are characteristic of this type.

ISO 6 - Reinforced Concrete Frame / Fire Resistive

A building where the structural floors and roof, and their supports are of materials such as precast or poured-in-place reinforced concrete, with a fire resistive rating of not less than two hours. Buildings classified as ISO Class 6 are characteristic of this type.