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Replacing Exterior Wall on a 6 Story Building

Dominic

Sawhorse
Joined
Jun 20, 2017
Messages
43
Location
Albany
A



The exerior wall is not a curtain wall.
The horizonal (floor/ceiling) UL assembly is G256. Code does not require the exterior wall to be rated. So it is not clear how to terminate the horizonal fire rated assembly to a non-rated exterior wall assembly.
 

steveray

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Nov 25, 2009
Messages
8,161
Location
West of the river CT
Code (2015 IBC) sucks on this because it doesn't give parameters for continuity like it does for walls, but a listed joint...basically...

715.1 General. Joints installed in or between fire-resistance rated
walls, floor or floor/ceiling assemblies and roofs or
roof/ceiling assemblies shall be protected by an approved
fire-resistant joint system designed to resist the passage of
fire for a time period not less than the required fire-resistance
rating of the wall, floor or roof in or between which the system
is installed. Fire-resistant joint systems shall be tested in
accordance with Section 715.3.
 

Dominic

Sawhorse
Joined
Jun 20, 2017
Messages
43
Location
Albany
Code (2015 IBC) sucks on this because it doesn't give parameters for continuity like it does for walls, but a listed joint...basically...

715.1 General. Joints installed in or between fire-resistance rated
walls, floor or floor/ceiling assemblies and roofs or
roof/ceiling assemblies shall be protected by an approved
fire-resistant joint system designed to resist the passage of
fire for a time period not less than the required fire-resistance
rating of the wall, floor or roof in or between which the system
is installed. Fire-resistant joint systems shall be tested in
accordance with Section 715.3.
Agreed there is no clear direction. I see what 715.1 is stating but this refers to joints between rated walls and floor/ceilings. In my case the exterior wall is not rated. In this case does the ceiling membrane (suspended ceiling in the ul assembly) just stop at the non-rated exterior wall?
 

steveray

Sawhorse
Joined
Nov 25, 2009
Messages
8,161
Location
West of the river CT
It stops, but to me, you have to treat the joint, or what is the point...I think they missed a bunch of stuff when the brought in the horizontal assemblies piece. Like if it is rated like a fire barrier, treat it like a fire barrier, if a fire partition, treat it as such...
 

Dominic

Sawhorse
Joined
Jun 20, 2017
Messages
43
Location
Albany
It stops, but to me, you have to treat the joint, or what is the point...I think they missed a bunch of stuff when the brought in the horizontal assemblies piece. Like if it is rated like a fire barrier, treat it like a fire barrier, if a fire partition, treat it as such...
I see you point. Thank you...
 

Dominic

Sawhorse
Joined
Jun 20, 2017
Messages
43
Location
Albany
I see you point. Thank you...
I reviewed 715.4 Exterior curtain wall/floor interstions. The code commentary states "Most fire-rated horizontal assembles are required to extend from outside wall to outside wall, that is from the inside faces of the exterior walls."....

This is all I can find. Now I am comfortable with my detail.

Thanks again. This was a big help bouncing this detail off everyone...
 

Dominic

Sawhorse
Joined
Jun 20, 2017
Messages
43
Location
Albany
How do you figure that it is a 3-hour rated floor assembly? The detail indicates it is 3 inches of concrete on a metal deck.

In order to get a 3-hour rating, the concrete would need to be at least 4.4 inches (at its thinnest location) using lightweight concrete. If using standard concrete, the thickness would need to be somewhere between 5.7 and 6.6 inches.

The most it could be is 1-hour, and if they used composite decking, then it would have no rating if the deck was not protected by fireproofing.

What is the recorded construction type of the building at the time it was built? Under the IBC, the construction type would need to be Type IB, which allows unlimited area and 12 stories for Group R-2.

Regarding the application of the IEBC, I would forgo using the work area compliance method and use the prescriptive compliance method per Section 503. The prescriptive compliance method is mostly focused on structural matters, and Section 503.1 allows you almost great latitude working with the new construction, provided that you do not make the building less compliant than it was prior to the alteration. Of course, all new construction must comply with the current code.

As for the exterior walls, non-combustible materials would definitely be required. The building does not comply with Type IIB or IIA for height (not sure where the building is area-wise since you did not provide that information), nor does it appear to comply with Type IB construction, which requires 2-hour floor construction and 2-hour construction for most other building elements. Thus, I would consider the building Type IIA (1-hour construction throughout) for all other code matters, which means you cannot add stories or increase the floor area since that would make the building less compliant than it was prior to the alteration.

Using Type IIA construction, 1-hour exterior walls would be required if the fire separation distance was less than 30 feet. If the fire separation distance is greater than 10 feet, then the walls need only have the rating for an interior exposure.
Ron,

Going back to your assumption of the 1 hour rating based on concrete thickness. Are you basing it on 3" of concrete minus 9/16" decking with a concrete thickness of 2 7/16"?
 
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