Fire Walls in Wood Framing

[SteelPE]

I am currently in the shop drawing review phase of a 4 unit apartment building (wood trusses supported by 2 story wood walls..... 2 levels of wood framed floors.... one being supported by wood, the other being supported by a poured in place concrete basement walls). Due to fire concerns, the architect needed to split the building into two separate units (each with two apartments) with a firewall separation in-between the two sections on the building.

During the shop drawing review process I noticed that the lumberyard threw out my details at he fire separation wall in lieu of some Simpson DHU hangers:

https://www.strongtie.com/firewallhangers_hangersforplatedtruss/dhu_hanger/p/dhu

I have never worked with these types of hangers before, so I am hesitant to start using them now. After speaking with the architect, he said that he changed the firewall requirements after talking to the building official and we now need to use these types of anchors (thanks for telling me now vs months ago buddy!).

My reservations with the hangers has to do with the fact that there is no floor on the opposite side of these hangers to "stabilize" the wall. That is, wall stability is now provided by these hangers being attached to the floor through the drywall and nothing else.

Has anyone used these hangers before? Should we be providing solid blocking in-between the studs for the hanger to attach to?

 

[jayrod12]

I believe they have a top flange mounted version of this which connects directly to the stud wall with a flange that projects through the drywall and then supports the joist seat. Maybe that one would make you feel better?

This one

 

[SteelPE]

jayrod,

Yes, they do.... and that would make me feel slightly better. I don't know if the architect is going to let me use those.

Have you ever used these before?

 

[jayrod12]

Yes I have used them before. To be honest we actually used USP's version instead of simpson because that's what the contractor preferred. It actually went pretty swimmingly. The guys on site liked them too.

 

[SteelPE]

Great,

Do you have to check the wall for any eccentricity due to the fact that the loads are not eccentric on the wall? Currently we have these walls as being axially loaded.

 

[jayrod12]

In my case, I had matching floors on each side of my firewall, so I ignored it (bad jayrod12). But in your scenario, if I'm understanding correctly, you have it on one side only and therefore I would take that into account. I don't think I'd go so far to consider the full half wall eccentricity, but maybe from the centre of the top flange of the hanger.