# Can two buildings divided by firewall share a common exit stair?



## AreaArch (Mar 8, 2021)

My building is subdivided with a firewall so each compartment is approx. 440 sq.m. and is 3 storeys. There are two exits stairs , on each corner. Can i give an exit stair in the center of both buildings as a shared exit stair?


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## steveray (Mar 8, 2021)

Yes...Probably...Do they have other exits?


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## AreaArch (Mar 8, 2021)

steveray said:


> Yes...Probably...Do they have other exits?


Each building has one exit stair.


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## cda (Mar 8, 2021)

AreaArch said:


> My building is subdivided with a firewall so each compartment is approx. 440 sq.m. and is 3 storeys. There are two exits stairs , on each corner. Can i give an exit stair in the center of both buildings as a shared exit stair?


Type of occupancy?

Why is the firewall there??

What is the rating??

May take someone from up north to answer the question


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## steveray (Mar 8, 2021)

AreaArch said:


> Each building has one exit stair.


Missed that....Concept is sound, but not familiar with Canada specifics...


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## AreaArch (Mar 8, 2021)

cda said:


> Type of occupancy?
> 
> Why is the firewall there??
> 
> ...


Type of occupancy is residential.
Firewall is given to sub-divide the building so it fall under the category which allow combustible construction.


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## e hilton (Mar 8, 2021)

The 440 sq m ... 4,000 sf ... is that per floor?   Entire residence?


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## cda (Mar 8, 2021)

AreaArch said:


> Type of occupancy is residential.
> Firewall is given to sub-divide the building so it fall under the category which allow combustible construction.



so is this built or concept?



Does up north have horizontal exit provisions


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## AreaArch (Mar 8, 2021)

cda said:


> so is this built or concept?
> 
> 
> 
> Does up north have horizontal exit provisions


It is just  concept now in schematic design stage. They do allow horizontal exit.


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## cda (Mar 8, 2021)

AreaArch said:


> It is just  concept now in schematic design stage. They do allow horizontal exit.




Unless you need or want a stair, you might look at that..


So how many units on each side of the wall???


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## TheCommish (Mar 8, 2021)

Can you maintain the integrety of the "fire wall" around the stair tower and have doors into it from both sides?


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## redeyedfly (Mar 10, 2021)

Sounds like a horizontal exit under IBC.  You may not need the center stair, the exit is at the firewall if you meet the horiz exit requirements.


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## steveray (Mar 10, 2021)

A horizontal exit is a lot more complicated than that...


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## redeyedfly (Mar 10, 2021)

steveray said:


> A horizontal exit is a lot more complicated than that...


More complicated than what?  Once you have the firewall all you need is refuge area and a standpipe.


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## steveray (Mar 11, 2021)

Two way communication....An additional smoke barrier unless the AOR is in the stair, and if that is the case, a large landing....Whatever else I am not thinking of right now...


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## tmurray (Mar 11, 2021)

Just to clarify, under the Canadian codes, this would still be considered a horizontal exit. The exit is the door in the firewall. Theoretically, if one building is on fire on one side of the firewall, the firewall will prevent the fire from spreading to the other side of the building. The only restriction is that a horizontal exit cannot account for more than half of the exits. In this case, assuming two is necessary for the floor area, this is acceptable. 

See 3.4.1.6 in the OBC


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## tmurray (Mar 11, 2021)

I might not have been clear enough...

On each side of the firewall you just need one set of stairs and a door through the firewall to the building on the other side.


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## cda (Mar 11, 2021)

tmurray said:


> I might not have been clear enough...
> 
> On each side of the firewall you just need one set of stairs and a door through the firewall to the building on the other side.




Need more info from the poster

Rating on the wall

how many units on each side

etc.....


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## tmurray (Mar 11, 2021)

cda said:


> Need more info from the poster
> 
> Rating on the wall
> 
> ...


Well, assuming it is a true firewall, not just a fire separation, it would be acceptable provided it is a minimum of 2 hours rating. If it is not constructed out of concrete or masonry, the fire resistive elements need to be protected from damage. Also needs to meet the structural requirements of a firewall. 

The number of units, or occupant load for that matter, does not restrict the use of horizontal exits.


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## e hilton (Mar 11, 2021)

tmurray said:


> . The only restriction is that a horizontal exit cannot account for more than half of the exits.


And the other half are ... vertical exits?


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## tmurray (Mar 11, 2021)

e hilton said:


> And the other half are ... vertical exits?


Other acceptable exits are...

exterior doorway
exterior passageway
exterior ramp
exterior stairway
a fire escape (must conform to 3.4.7. which does not allow them for new buildings)
an interior passageway
an interior ramp
an interior stairway

in this case, they have an interior stairway that is their other half.


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## redeyedfly (Mar 11, 2021)

steveray said:


> Two way communication....An additional smoke barrier unless the AOR is in the stair, and if that is the case, a large landing....Whatever else I am not thinking of right now...


Those requirements are for I occupancies, OP stated it was residential.  

Horizontal exits are really straightforward (under IBC) and are a very common MOE for buildings separated by fire walls.


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## steveray (Mar 12, 2021)

redeyedfly said:


> Those requirements are for I occupancies, OP stated it was residential.
> 
> Horizontal exits are really straightforward (under IBC) and are a very common MOE for buildings separated by fire walls.


So it is your position that a refuge area is not an area of refuge?

1026.4 Refuge area. The refuge area of a horizontal exit
shall be a space occupied by the same tenant or a public area
and each such refuge area shall be adequate to accommodate
the original occupant load of the refuge area plus the occupant
load anticipated from the adjoining compartment. The
anticipated occupant load from the adjoining compartment
shall be based on the capacity of the horizontal exit doors
entering the refuge area.

1009.6 Areas of refuge. Every required area of refuge shall
be accessible from the space it serves by an accessible means
of egress.
1009.6.1

1009.6.4 Separation. Each area of refuge shall be separated
from the remainder of the story by a smoke barrier
complying with Section 709 or a horizontal exit complying
with Section 1026. Each area of refuge shall be
designed to minimize the intrusion of smoke.
Exceptions:
1. Areas of refuge located within an enclosure for
interior exit stairways complying with Section
1023.
2. Areas of refuge in outdoor facilities where exit
access is essentially open to the outside.
1009.6.5 Two-way communication. Areas of refuge shall
be provided with a two-way communication system complying
with Sections 1009.8.1 and 1009.8.2.

AREA OF REFUGE. An area where persons unable to use
stairways can remain temporarily to await instructions or
assistance during emergency evacuation.


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## cda (Mar 12, 2021)

steveray said:


> So it is your position that a refuge area is not an area of refuge?
> 
> 1026.4 Refuge area. The refuge area of a horizontal exit
> shall be a space occupied by the same tenant or a public area
> ...






"""So it is your position that a refuge area is not an area of refuge?""""



That is a true statement. I got schooled on that. Not sure why the code writer's god, uses similar terms


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## cda (Mar 12, 2021)

> cda said:
> 
> 
> “continuous and unobstructed way of egress travel from any point in a building or facility that provides an accessible route to an area of refuge, a horizontal exit or a public way.”
> ...


You're confusing an "Area of Refuge" with the horizontal exit's "refuge area." These are two completely different things.







						Horizontal Exit Refuge Area
					

“continuous and unobstructed way of egress travel from any point in a building or facility that provides an accessible route to an area of refuge, a horizontal exit or a public way.”    [BE] AREA OF REFUGE. An area where persons unable to use stairways can remain temporarily to await...



					www.thebuildingcodeforum.com


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## steveray (Mar 12, 2021)

Soooooo.....When would you EVER apply both principals.....

Commentary......
Although similar
language is used in describing the “area of refuge” for
an accessible means of egress, Section 1009.6 specifies
area requirements that are insufficient for use as
a “refuge area” for a horizontal exit. Care must be
taken where applying both principles to the same horizontal
exit.


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## cda (Mar 12, 2021)

steveray said:


> Soooooo.....When would you EVER apply both principals.....
> 
> Commentary......
> Although similar
> ...




When the building design either uses both???   Or requires both????


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## redeyedfly (Mar 12, 2021)

steveray said:


> So it is your position that a refuge area is not an area of refuge?


Yes.


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## steveray (Mar 12, 2021)

Most of the designers here balk at the standpipe for some reason...Unless the HE goes into a stair and it is already there....


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