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).

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

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


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

Modified Fire Resistive (ISO Class 5, IBC Type IB)