Type II structures tend towards larger structures or hazard limited structures. Type IIA is more restrictive than Type IIB, but allows for larger areas as a trade-off.
Firstly, all bearing elements (columns, beams, shearwalls, bearing walls…) must be non-combustible. Type IIA also requires that all bearing elements be 1-hour fire-rated in addition to being non-combustible.
Just for the record, non-combustible refers to an element’s resistance to catching fire. Fire-rated refers to amount of time it takes for a full fire (around 1,000 degrees F applied to a sqft or more of the wall surface) to set combustible material (think paper) on fire due to the transfer of heat. This is measured in 1 hour increments up to 4 hours, and some scenarios also use smaller increments.
In most cases using Type IIA will allow between 30%-50% more square footage before requiring separation walls and barriers, but to be honest, the inclusion of fire sprinklers makes a bigger difference.
MKDesign 