# Fire Partition Walls- details



## Stepheneckert (Dec 16, 2022)

I'm working on a 10 unit stacked flat- three story residential building.  It requires a 1 hour fire partition wall, NOT a fire wall between units.  We are using AAC (autoclaved concrete blocks) as the partition wall continuous from foundation through to parapets.  The structure is not isolated- meaning all floors bear on the same wall side to side- not a double wall. My questions is will this work?  My structural engineer says we cant do that- we need to isolate the structure on both sides.  I'm pretty sure he is wrong, I just cant 100% prove it.  Anyone know the answer?  Thanks!!

Stephen


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## Jay Smith (Dec 16, 2022)

2021 IBC 420.2 requires the separation walls to be built as fire partitions in accordance with Section 708. There is nothing in that about separate structures. I will say, though, I almost always see the unit separation wall done as two stud walls.


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## TheCommish (Dec 17, 2022)

"It requires a 1 hour fire partition wall, NOT a fire wall between units."

Please cite section


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## Inspector Gadget (Dec 19, 2022)

In Canadian Codes, insetting joists into a concrete/masonry/block wall with a fire rating is acceptable, as long as the remaining material is sufficient to provide the required fire-resistance rating.
In our system, we have a fairly intense formulaic process for calculating FRR of common assemblies independent of ULC testing (Appendix D). I have no idea what IBC/ICC might allow, but in Canadian code, three inches of type S mortar/concrete is sufficient to provide one hour of FRR.


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## tmurray (Dec 23, 2022)

Stepheneckert said:


> I'm working on a 10 unit stacked flat- three story residential building.  It requires a 1 hour fire partition wall, NOT a fire wall between units.  We are using AAC (autoclaved concrete blocks) as the partition wall continuous from foundation through to parapets.  The structure is not isolated- meaning all floors bear on the same wall side to side- not a double wall. My questions is will this work?  My structural engineer says we cant do that- we need to isolate the structure on both sides.  I'm pretty sure he is wrong, I just cant 100% prove it.  Anyone know the answer?  Thanks!!
> 
> Stephen


What is his code section?


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