Joisted Masonry is one of six building construction categories established by Insurance Services Office, Inc. (ISO). These six categories are part of the Commercial Lines Manual (CLM) and is designed for the purpose of developing rates for insuring commercial property bas upon the likelihood of damage by fire. The CLM description of Joisted Masonry Construction is considered a building with exterior walls of masonry or fire-resistive construction equipment rated for not less than one hour and with combustible floors and roofs.
This classification includes worked done on exterior walls with combustible floor and roof. The types of materials used in these walls include adobe, brick, concrete, gypsum block, hollow concrete block, stone, tile, or other similar materials. The code associated with Joisted Masonry Construction ranks a facility 1-6 based upon how fire resistant the facility is that the business is located or is working on.
ISO Class 1 is Called Frame.
Exterior walls of wood, brick veneer, stone veneer, wood ironclad, or stucco on wood. (Construction Code 1)
ISO Class 2 is Called Joisted Masonry.
Exterior walls of masonry material (adobe, brick, concrete, gypsum block, hollow concrete block, stone, tile, or similar materials) with combustible floor and roof.
ISO Class 3 is Called Non Combustible
Exterior walls, floor, and supports made of metal, asbestos, gypsum, or other noncombustible materials.
ISO Class 4 is Called Masonry Non Combustible.
Same as joisted masonry except that the floors and roof are of metal or other noncombustible materials.
ISO Class 5 is Called Modified or Semi Fire Resistive.
Exterior walls, floors, and roof of masonry or fire-resistive material with a fire resistance rating of at least 1 hour but less than 2 hours.
ISO Class 6 is Called Fire Resistive.
Exterior walls, floors, and roof of masonry or fire-resistive materials with a fire resistance rating of at least 2 hours.