CMU Firewall & Steel Joist

[msdengineer]

Is it permissible to have a one-hour interior firewall that has penetrations for a deep span steel joist framing past the wall on either side?

I have a 67'-6" span out to out of masonry exterior walls and an interior 1-hour firewall parallel to the exterior walls offset in about 10'-0" ea. side of the building. Is it permissible to run the steel joists out to out of the exterior walls and treat the firewall as a non-load bearing partition with penetrations for the joist to pass thru? Or will it be necessary to use the firewall as a load bearing wall and stop the framing on ea. side of it to create in essence 2 structures in case of fire? The building is sprinklered if it makes a difference.

 

[JAE]

I think the idea of a firewall is that the fire on one side of the wall can demolish the structure (complete collapse) and the firewall holds it back from damaging the structure on the other side.

With a joist spanning through the firewall you would probably have a half of a joist remaining that wasn't designed to bear on the firewall and would be unstable, defeating the purpose of the firewall.

 

[jike]

Check the code to see if this is actually defined as a "firewall" or another name.

 

[msdengineer]

Thanks for the responses, I do have a followup question though.

Does the type of firewall make a difference. For example, can a 1-hour firewall be penetrated, but not a 3-hour?

 

[JLNJ]

If it's a firewall and not a fire separation wall I can't imagine that it is within the spirit of the code to permit such a penetration. If it's just one hour I doubt that it's a true fire wall.

A firewall needs to be able to survive collapse of the structure on either side without damaging the integrity of the fire separation. This means that the wall and structure on one side needs to remain in place with its fire rating intact after collapse of the structure on the other side. This includes accounting for whatever "pulling" forces might be encountered when one side fails due to fire.

The only place I've seen these pulling forces attempted to be addressed is in some recent FM documents. They have a methodology for determining these forces and they provide some details which they hope make the interface work as they assume. I don't believe they have any sort of details where the wall is in the middle of the beam span.

All that said, I've seen some absurdly optimistic assumptions from architects about how to accomplish a "fire wall" and I've seen one Building Official permit such details while another BOs says "no way". To me it seems to be shaky ethical grounds to submit for a permit something which you know does not meet the intent of the code yet you are hoping it slips through on approval. I've seen this attempted more than once in schools. A school! You'd think that a school would be the last place to attempt to get over on the Building Official.