Masonry Noncombustible

Construction types

Masonry Noncombustible (ISO Class 4, IBC Type IIA)

Masonry Noncombustible construction is ISO Class 4. ISO Class 4 encompasses IBC Type Type IIA (protected).

Learn the elements of masonry non-combustible construction. Masonry non-combustible buildings are buildings with exterior walls of masonry material and with noncombustible or slow burning floors and roofs.

buildings with exterior walls of masonry — not less than four inches thick, or
buildings with exterior walls of fire-resistive construction — with a rating of not less than one hour, and
noncombustible or slow-burning floors and roofs — regardless of the type of insulation on the roof surface

Note the advantages of noncombustible construction:
Uses floors and roof supported by superior exterior bearing members that provide for stability and are less likely to collapse during a fire
Uses materials that don’t readily burn

Note that masonry noncombustible construction has these disadvantages:
Uses unprotected steel for interior members of floors and roof, and steel loses strength and becomes less stable and more damageable at high temperatures
Uses slow-burning materials that do burn — adding fuel to a fire

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