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RBK
August 9th, 2011, 16:06
2009 IBC
706.2 Structural stability. 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.

I have heard this described as requiring the fire wall to be structurally independent, though that isn't the exact wording.

But section 706.9 allows pentrations per 713, which are basically the same as for any other fire-rated assembly. So, how do you maintain structural independence with building utilities penetrating a fire wall?

The situation I am looking at deals with a fire wall used as a horizontal exit, and the requirement to provide standpipe connection on either side of the exit. It has been suggested that the pipe supplying the standpipe cannot penetrate the fire wall because that would not meet section 706.2.

Any thoughts?

mtlogcabin
August 9th, 2011, 17:43
1025.2 Separation.
The separation between buildings or refuge areas connected by a horizontal exit shall be provided by a fire wall complying with Section 706; or it shall be provided by a fire barrier complying with Section 707

707.5 Continuity.
Fire barriers shall extend from the top of the floor/ceiling assembly below to the underside of the floor or roof sheathing, slab or deck above and shall be securely attached thereto. Such fire barriers shall be continuous through concealed spaces, such as the space above a suspended ceiling.

RBK
August 9th, 2011, 18:32
You will have to pardon my ignorance of building code, but isn't a fire wall different than a fire barrier? Can a fire barrier still be used to create separate buildings?

mtlogcabin
August 9th, 2011, 18:55
Can a fire barrier still be used to create separate buildings?
No but it can be used to create a horizontal exit. Do they need to be seperate buildings?

RBK
August 9th, 2011, 19:31
I think so. It's a pretty bid building. It's a type V-A, 4-story, with a total area somewhere around 280,000 sq. ft. I think there are 5 separate building areas in the current plan.

mtlogcabin
August 9th, 2011, 20:01
280,000 sq ft V-A 4 stories

What is the occupany group?

It might be cheaper to up the construction Type in lieu of all the structurally independent fire walls 4 stories tall. I don't see how you can accomplish this.

RBK
August 9th, 2011, 21:21
It's a large scale apartment complex. Occupancy is mostly group R-2, with some A-3 & B for amenity areas and leasing office. I see quite a few of these, but most are on top of a subterranean parking garage so there isn't really a need to cross the fire walls with the large utilities. This one is on grade and there is a separate parking structure.

The problem I have is reconciling 706.2 with 706.9. How can penetrations be allowed through the fire wall, and still maintain the structural independence? Is it assumed that by the time the building collapses on one side of the wall, the utility lines are destroyed, or pretty much useless anyway? Does that assumption extend to a standpipe system, that may still be in use when the building collapses?

Paul Sweet
August 9th, 2011, 22:28
Firewalls don't have to be structurally independent. They just have to be detailed so that if the construction on one side collapses it doesn't pull the fire wall down with it. Two typical ways of doing this are: For a masonry wall with wood joists perpendicular to it, the ends of the joists are fire cut. For a double stud wall with a rated gypsum shaftwall the gypsum board is attached to the wood framing with aluminum clips that melt in a fire.

TJacobs
August 10th, 2011, 11:47
You will have a hard time finding a drywall shaft wall that can go 4 stories or more than 40 feet...maybe a precast shaft wall (thermacrete).

brudgers
August 10th, 2011, 12:10
You will have a hard time finding a drywall shaft wall that can go 4 stories or more than 40 feet...maybe a precast shaft wall (thermacrete). USG Area Separation Walls are good for 44'.

Setting it on top of a different wall type such as CMU would allow for taller construction.

http://www.usg.com/rc/system-catalogs/usg-area-separation-walls-catalog-en-SA925.pdf

RBK
August 10th, 2011, 12:14
Firewalls don't have to be structurally independent. They just have to be detailed so that if the construction on one side collapses it doesn't pull the fire wall down with it. Two typical ways of doing this are: For a masonry wall with wood joists perpendicular to it, the ends of the joists are fire cut. For a double stud wall with a rated gypsum shaftwall the gypsum board is attached to the wood framing with aluminum clips that melt in a fire.

What about the utilities that cross the wall? If a 6" steel pipe crosses the wall, and one side of the building comes down, that 6" pipe is going to do some significant damage on the other side of the wall. I don't think they make any pipe couplings that are made to melt in a fire.

brudgers
August 10th, 2011, 12:50
I have heard this described as requiring the fire wall to be structurally independent, though that isn't the exact wording. The description you have heard is incorrect.

The code says what it says.

brudgers
August 10th, 2011, 12:51
What about the utilities that cross the wall? If a 6" steel pipe crosses the wall, and one side of the building comes down, that 6" pipe is going to do some significant damage on the other side of the wall. I don't think they make any pipe couplings that are made to melt in a fire. Run the pipe below the wall.

Builder Bob
August 10th, 2011, 14:42
What about the utilities that cross the wall? If a 6" steel pipe crosses the wall, and one side of the building comes down, that 6" pipe is going to do some significant damage on the other side of the wall. I don't think they make any pipe couplings that are made to melt in a fire.

Then I think the fire wall has done its job and allowed everybody plenty of time to get out of the structure..... after a fire, the firewall would have to be rebuilt anyway.....

Really don't see an issue as the firewall is not designed to remain there if the fire has damaged the surface of the wall exposed to the thermal heat of the fire. concrete, gypsum, masonry, or any other building material would be severely affected by the heat exposure because of the removal of water in the construction materials... these material would then become brittle and not have the tensile strength that they had before the fire/heat exposure.

Codegeek
August 11th, 2011, 11:47
If the fire wall is designed utilizing a UL listed assembly which is a load-bearing wall, then there should be a corresponding assembly for the through penetration firestop system. For example, U921 is listed as a three hour bearing wall. C-AJ-1523 allows for a maximum diameter opening of 7 1/4 inches in a CMU assembly.

So, yes, you can have the penetration and still comply with 706.2.