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two hour wall

C

cda

Sawhorse 123
Joined
Oct 19, 2009
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Sorry not at the office so no code reference, and have seen the topic before, just have not had to deal with it.

The requirement for a wall to stay up if the other side collapses. HOw do you see this accompolished in the field???

The set up is existing building, that will be added on to, with two hour wall, and another complete building added to the existing, at the two hour wall.

Someone did not anticipate the question of collapse being asked!!!!!

It is IIB construction if that helps any. They are over allowable area with all adds already calced in.

This is what I am trying to say::: '''''The 2 hour fire wall has to be structurally independent as per 705.2

(Fire walls shall have sufficient structural stability under fire conditions to allow collapse of construction on either side without collapse of the wall for the duration of time indicated by the required fire-resistance rating.)"""""""
 
Re: two hour wall

Shaft wall with aluminum "melt away" clips is the most common/inexpensive, or a nonbearing masonry wall would also accomplish the goal, allowing either building to collapse and the other to stay intact. I don't have a UL# right now, but shouldn't be too hard to find online.
 
Re: two hour wall

I am seeing more "double walls" where one fire wall is tied into each separate "building". If one "building" collapes, it will take its fire wall with it. However, the second wall associated with the other "building" will survive. The change in the 2009 IBC that requires lateral and seismic bracing to have the same fire resistive rating as the fire wall will probably lead to more double walls. I am not a structural engineer, but this is what they are concluding. 2006 required the gravity loads to be rated, but you could use the non rated building frame as a part of the seismic design. 2009 no longer permits this.
 
Re: two hour wall

Are you impying that there could be an Earthquake AND a fire at the same time?

Wholly Hot Rattling Windows Batman! What NOW?! :eek:

cda - Basically, you want to avoid framing that is continuous through the fire wall, or that is interdependant on framing on the other side of it (like roof trusses that straddle it... :? ). With an addition you're really primarily concerned with the 'new' construction and what holds up the wall if/when the 'old' side collapses.
 
Re: two hour wall

Try Gypsum Association GA File No. ASW 1500 or equivalent. This 2- hour resistant assembly is located between the load bearing walls, allowing the designer freedom to use the walls as necessary.
 
Re: two hour wall

JD

The 2009 IBC now requires lateral bracing to have the same fire resistive rating regardless if it carries a gravity load. While it used to be "shake then bake" it is now "shake and bake"
 
Re: two hour wall

C D - Our State version of the '06 I-Codes was due out in '09, now pushed to '11. Won't see a modoified '09 for quite a while yet. ;)
 
Re: two hour wall

John - actually, earthquake+fire+aftershock is a common scenario, as gas lines break, vehicles crash, powerlines spark, etc.

After the 1994 Northridge (Los Angeles) quake, there was an L.A. Times photo of of a street fissure where both the water and gas lines had broken. Power lines were down, the street was flooded, and flames were shooting up out of the water. Earthquake+flood+fire... all we needed was a plague of locusts, or perhaps another riot.
 
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