Stair framing supported by a concrete fire wall.

[Tim Mailloux]

165K sf Elementary school project in CT, 2018 CT code (amended 2015 IBC), type 2B construction, 2 stories with sprinklers……

Due to the size of the building footprint we had to chop it up into (5) individual zones using 2 hour rated fire walls. The fire walls are structurally independent cast in place concrete. At two locations we have enclosed exit stairs adjacent to the fire walls, with the fire wall making up (1) of the (4) sides of the exit enclosure. The contractor would like to embed some steel plates into the fire wall pour to attach the upper & intermediate stair landing to. The. Generally we don’t like to attach anything to fire walls, however in this case I can sort of get onboard with it.

 

[Tim Mailloux]

one more thing to add, the stair tower enclose is masonry and also structurally independent.

 

[steveray]

Is there a question there Tim?...Generally, as long as there is enough concrete/ masonry behind the penetrant, I do not consider it a penetration....Not sure if you are talking FW or exit enclosure requirements...

 

[Tim Mailloux]

we just usually go out of our way keep fire walls independent or everything, so I am having a hard time wrapping me head around attaching the stair landings to it.

 

[steveray]

As long as you are good saying that the stairs can fall and shouldn't pull down the FW, you are good....

 

[Yikes]

we just usually go out of our way keep fire walls independent or everything, so I am having a hard time wrapping me head around attaching the stair landings to it.

Are you concerned that the embedded plates will transmit heat either through the wall or that it will lead to the incineration of concrete surrounding the embeds?

I've never seen a fire wall for area separation that was truly independent of everything. At a minimum, I often see embeds for attaching ledgers at the roof.

 

[RLGA]

My concern is less with the penetrating, embedded item since they are typically solid-grouted. My concern is along the lines of that pointed out by @steveray--if the stairs collapse, will they compromise the fire wall?

 

[steveray]

The whole firewall "structural stability" allowing collapse on either side is just a concept...Who knows what is actually happen based on a particular fire or disaster....We can guess on what is likely, but there is no listing or tested "thou shall not collapse" detailing...

 

[Tim Mailloux]

My concern is less with the penetrating, embedded item since they are typically solid-grouted. My concern is along the lines of that pointed out by @steveray--if the stairs collapse, will they compromise the fire wall?

the fire wall is 12" thick cast in-place concrete, if the stair were to collapse I don't forsee a light weight steel pan stair doing any damage to it. Additionally the 1 hour rated stair enclosure is structurally independent CMU on 3 sides with the 4th side being the CIP fire wall.. The unprotected structure around the stair enclosure would collapse in a fire before either the 1 hour rated stair enclosure or the 2 hour rated fire wall.

 

[Tim Mailloux]

The whole firewall "structural stability" allowing collapse on either side is just a concept...Who knows what is actually happen based on a particular fire or disaster....We can guess on what is likely, but there is no listing or tested "thou shall not collapse" detailing...

I have a buddy thats an engineer at FM Global, he tells me they are working on this test

 

[jar546]

the fire wall is 12" thick cast in-place concrete, if the stair were to collapse I don't forsee a light weight steel pan stair doing any damage to it. Additionally the 1 hour rated stair enclosure is structurally independent CMU on 3 sides with the 4th side being the CIP fire wall.. The unprotected structure around the stair enclosure would collapse in a fire before either the 1 hour rated stair enclosure or the 2 hour rated fire wall.

It has been my experience working with Factory Mutual that true firewalls must remain independent and although penetration are only allowed in the lower 36" of the wall, any attachments were to be plastic shielded so that it melts and falls away, right down to our conduit straps, etc.

 

[TheCommish]

To my knoledge there is nothing the prohibits pipes properly sealed from penetrating through the fire wall so attachijng to it does not cause me any problem

 

[RLGA]

the fire wall is 12" thick cast in-place concrete, if the stair were to collapse I don't forsee a light weight steel pan stair doing any damage to it. Additionally the 1 hour rated stair enclosure is structurally independent CMU on 3 sides with the 4th side being the CIP fire wall.. The unprotected structure around the stair enclosure would collapse in a fire before either the 1 hour rated stair enclosure or the 2 hour rated fire wall.

If the wall is 12-inch-thick concrete and only two stories, then I personally would not have a problem with an anchor in the wall.