Wood floors and a 1hour stair wall

[mijowe]

Ok, I have a wood frame building used for "light" office. I have two stair towers in the corners of the building that require a 1Hr interior wall, and a floor that does not need to be rated (I am taking the architects word for this). Both the wood frame stairs, and the wood floor will be framing/bearing on the wall. The floors have some decent spans 26' trusses, so the reaction is fairly high for a wood framing.

I typically use CMU or a double wood wall with a gypsum separation wall between. However this building is so small neither are cost effective or practical. I am also not a big fan of trying to get the hanger to bridge over the gap of the 5/8" drywall.

Anybody have a detail, or experience in dealing with this?

 

[bdSE]

This comment won't help much with the framing, but please be aware that when some rated wood walls are fire rated, the load used during the test could have been below the allowable load of the wall. Meaning, when the rated wall assembly was tested, it could have been loaded to a certain amount, not to the full structural capacity of the wall. Therefore, you need to make certain that your stud stresses remain below this particular value to ensure that the wall retains its true rated value.

I have been trying to find a good source of information for you to reference, but in the mean time you should begin with finding out which rated assembly your architect intends to use and try to look up specific information regarding that specific assembly.

For example...

http://www.awc.org/Publications/dca/dca3/DCA3.pdf

shows a few examples. Most of which are rated to 100% load capacity, but this is not often the case with the UL rated assemblies I have seen.

Just for additional information, how many stories are intended for this project.

 

[Ron]

It is likely that your floors must be rated, particularly if there is separation between floors that divides tenants or occupancies.

For the firewall joist support, you essentially have two choices:

1. Use hang-over joist hangers with reduced load capacity for the drywall gap.

2. Use fire-retardant treated plywood over the joists and butt the gypsum to the plywood, sealing the joint with fire rated foam or putty.

 

[mijowe]

Thanks, both helpful comments. I do have in my hand a Simpson hanger capacity hanging over 5/8" gyp.