What is supporting construction? Columns and beams only or does it include bar joists?

[Sharlene]

There is no definition in the 2015 IBC for supporting construction. Is it defined as columns and beams or does it include the bar joists?

Building is type VB, sprinklered. I am trying to provide a 1 hour floor assembly to separate occupancies. In the 2015 IBC, 711.2.3 Supporting Construction. The supporting construction shall be protected to afford the required fire-resistance rating of the horizontal assembly supported. Exception: In buildings of Type IIB, IIIB, and VB construction, the construction supporting the horizontal assembly is not required to be fire-resistance rated at the following: Horizontal assemblies at the separation of dwelling units and sleeping units as required by Section 420.3. I'm trying to provide the one hour separation for the floor only without doing anything to the bar joists below.

 

[steveray]

In that case, the floor system would have to be a 1hr assembly which would include the joists, (Horizontal assembly)....But not the beams and columns...that support the floor system.

 

[tmurray]

Here, if something is fire rated, everything that supports that something must be fire rated to the same level.

Makes no sense to require a 1 hour floor system if the columns holding it up fail after 30 minutes.

 

[steveray]

I almost typed that this was a bad code change, but I stayed away....Maybe they figure that the supporting members+ sprinklers in R will make it work? Another sprinkler gimme?