Type IIB vs Type IIIB Construction

[retire09]

Why does table 601 require 2 hour exterior walls for type IIIB and 0 for type IIB Construction?

What is the construction type of your typical metal building S-1/B occupancy with interior partition walls of combustible wood stud construction?

 

[Plans Approver]

A long time ago someone told me that III-B was part of the code to cover typical commercial construction of pre-50's type. Where the exterior walls were built on fairly narrow lots and the building usually had a store on the first floor and the proprietor's dwelling on the upper floors. The exterior walls constructed of masonry with the interior walls, floors and roof constructed of wood. Typical of many quaint, old town square buildings.

II-B is all non-combustible construction with the exceptions in 603.1.

What is the construction type of your typical metal building S-1/B occupancy with interior partition walls of combustible wood stud construction?

I would classify it as Type V-B. If the studs are fire retardant treated, nonbearing, and 2 hour or less or no rating required then it could be Type II-B.

 

[TJacobs]

There is a much greater fire load within Type III because the structure contributes to the fire.

 

[Builder Bob]

A typical Type III-B building is the ordinary construction that is seem on main street USA that was built using multiwythe brick walls with joist pockets where the floor and/or ceiling joist were firecut.

The new version of Type III-B construction will lead down multiple paths without any one answer being correct since it will be the local AHJ that has the final say so---

However, it was the interpretation where I worked before that as long as the load bearing columns and and required wind bracing for a building was rated for two hours --- the purlins and sheet metal veneer did not have to be rated since it was not a part of the load bearing assembly.

As I stated above - the interpretation above may differ greatly from your AHJ....