Area Separation walls and Pre-Engineered structures ?

[JJH57]

I'm a little out of my comfort zone with this one. I'm helping a friend of mine grind through a permitting process on a small building. The Building is a 40' x 60' x 22' Pre-Engineered building 4:12 roof with 3 20' bays. the building is insulated with batt insulation and heavy insulation facing over the purlins (On the living side - similar to a simple saver system) The building is classed as S-1 occupancy. In one bay of the building he wants to add a mezzanine - so the mezzanine would be roughly 21' x 40'. The stated purpose of the mezzanine is small apartment where a couple workers can spend the night if needed (the building is for a flooring contractor in a rural area, he's trying to provide a place for an install crew to spend the night if they need to and save them the costs of a hotel.)

The deflection criteria of the main frame would allow deflections of up to 2-1/2".

Since this is S-1 to R-1 the mezzanine has to be separated by a 2 hour wall from the S-1 area. The mezzanine also has to have 2 hr protection on the underside as the first level would still be classified as S-1. We are planning on a UL301 wall assembly - 2x6 wood framing, insulated, 2 layers of 5/8 type x on each face.

I'm struggling with finding a UL Head of Wall condition. As I understand the IBC, (the jurisdiction is under IBC 2009.) It's permissible to terminate an area separation wall at a non-combustible roof. What I planned on doing was fastening 5x5x1/4" angles to the underside of the purlins and sandwiching the wall between the angles leaving 2-1/2" clear between the purlins and the top plate. The angles would be stout enough to carry sideloading on the wall. The resulting cavity could be filled with mineral wool. The wall is offset from the frame to eliminate having to do all the framing required to protect the frame specifically. The HW-D assemblies I can find all show the roof /floor having an equal or greater fire rating than the wall. The code official wants a UL assembly specified.

 

[stookeyfpe]

Did the code official mention the required fire sprinkler system? That introduces another load path. Your client has a Group R fire area. The building requires fire sprinkler protection.

 

[ajh1]

There are 3 head of wall assemblies that MBMA had tested at UL. They are HW-D-0488, HW-D-0489, and HW-D-0490. Unfortunately, these are each 1-hr ratings. I'm not of aware of anything with a better rating with an unrated roof assembly.