1. Frame (Class 1)
In Frame Construction, the building’s exterior walls, floor, and roof are made of wood (or various composition boards). Frame construction also includes buildings with a wood floor and roof but with exterior walls of non-combustible or slow-burning construction such as vinyl, metal cladding or masonry veneer (that is, layers of brick, stone or stucco). These exterior wall coverings are fastened to a wood frame and are used for appearance rather than structural support.
2. Jointed Masonry (Class 2)
In Joisted Masonry construction, the exterior walls are masonry – such as brick, concrete, hollow block, or stone. The roof – and the joists and beams that support the roof – are made of wood or other combustible materials.
The floor is made of wood or concrete. Joisted masonry buildings most often seen by our loss control consultants are those with floors of concrete rather than wood – and have masonry walls and wood roofs.
3. Non Combustible (Class 3)
Buildings rated Non Combustible are those with walls, floors, and roof made of non-combustible or slow-burning materials. The building supports – that is, columns, beams, joists – are structural steel. Buildings in the class are frequently all metal – that is, steel on steel. Buildings that have iron and glass walls – such as many office buildings where the walls are mostly or entirely glass – would be considered slow burning and classified as Non Combustible.
4. Masonry Non Combustible (Class 4)
Buildings in the Masonry Non Combustible class have walls of masonry (no less than four inches thick). (Walls could also be of fire resistive construction with a rating not less than 1 hour), and floor and roof of non-combustible or slow burning materials. The typical Masonry Non Combustible building has masonry walls, a concrete floor, and some types of metal deck rook, and unprotected steel beams, columns and bar joists.
5. Modified Fire Resistive (Class 5)
Buildings in the Modified Fire Resistive class have exterior walls, floors, and roof of masonry material with a fire resistance rating of at least 1 hour but less than 2 hours. Modified fire resistive buildings also include structures that employ structural steel protection techniques – that is, fire-protection material applied to steel. Materials include concrete, plaster, clay tile, brick and gypsum block among others.
6. Fire Resistive (Class 6)
Buildings in the Fire Resistive is constructed of masonry of fire resistive material with a fire resistance rating of 2 hours or more and it less likely to buckle. Examples include high rise office buildings and condos, and parking garages.