steel beam fire protection

[dbriant]

I have a building with the lower floor being steel beam / joist construction supporting 2 floors of wood bearing walls. The typical exterior beam detail is to have the wood top plate bolted through the bottom flange of the steel beam. This conflicts with generic architectural fire protection details that require primary members to be wrapped with 2 layers of gyp board. Along the bottom flange, they show a 1 5/8" steel studs as a gap between the gyp board and the bottom flange. Sketches attached

The lower level exterior wood walls are not load bearing, nor are they shear walls, however they need to be adequately anchored to the steel beams for wind loads. Any thoughts on a detail to connect through the gyp board system? A different option we've proposed is to go with intumescent paint on the steel beams but the contractor is balking at this since it would cost more.

Thanks for any insight.

 

[jayrod12]

Why not frame the lower non-load bearing partition out of steel stud? Then you can have clips that project up through the 2 layers of gyp to the underside of beam.

 

[dbriant]

Using metal studs is an option that I'll propose for future projects, however this project is currently under construction which limits some of the available options like insetting the steel structure and running the walls past the steel to the floor deck. The main portion of this building is framed with wood studs, which was deemed more economical than metal studs at the beginning of the project. Switching to steel studs would require bringing in another subcontractor and the walls would be 3/4" thicker than originally detailed with wood.

 

[jayrod12]

Where I am, I can get steel studs to match the depth of wood studs.

Unfortunately, I don't really have a great option for you. What about providing a plate or similar that extends down on the backside of the stud wall, this could be wrapped in drywall and then you fasten through the gyp.

 

[DETstru]

What are you doing about deflection of the steel beam? You need separation to allow the steel beam to deflect without crushing the wood below wall.