Horizontal Continuity of a Fire Wall

[retire09]

I have a plan submitted for a large addition to a church. In an effort to avoid sprinklers, the architect has provided a fire wall to create two separate buildings. The fire wall extends to the exterior side walls of the existing building with a 1 hour wall 4' back at each corner (one side only perpendicular to the fire wall). The problem is, the addition is 30' wider than the existing building and where the fire wall stops and turns back 4' along the existing sidewalls, the new exterior wall for the addition continues another 15' on each side.

In order to create two separate buildings with a fire wall, does the wall not have to extend to the limits of the wider of the two separate buildings created?

 

[gbhammer]

Myself and one of our fire marshals have asked the council that very same question and we received two diferent answers. I say no the wall does not need to continue.

 

[gbhammer]

Think about this.

What if the RDP continued the wall so as to have more linear footage when calculating the percentage of openings allowed in the rated wall?

 

[JustReid]

Are they creating a "fire wall" for separate buildings? or providing a "fire barrier" to create separate fire areas? They are different, and the fire barrier could be used to alleviate the need for sprinklers based on fire areas making a fire wall unecessary (and all the rules that come with it). Unless the fire wall is being provided for more than just sprinklers (construction type, area, etc.). And yes I agree that either would not need to extend past the shorther wall as long as the termination rules are followed.

 

[retire09]

The addition has door openings on each side adjacent to the corners of the existing building. The doors exit through what I beleive should be the continuation of the fire wall. These doors open onto a wood deck under a roof overhang on the existing building.

A fire could burn around the fire wall on the exterior of the building under the roof overhang on the wood deck of the existing building.

 

[JustReid]

The overhang would change things if this is considered building area of the existing portion. (See definition Area, Building Chapter 5). That area would also require separation from the new.

 

[texasbo]

Very interesting question. When looking at the fire wall being just part of the more narrow building, it's easy to conclude that it would only have to extend 4' beyond the perpendicular exterior walls.

However, the fire wall is also part of the wider building. The code says it must extend from exterior wall to exterior wall. So when looking at the wide building, wouldn't the fire wall have to extend from exterior wall to exterior wall? Can you just terminate a fire wall in the middle of a wall run, without it extending to the exterior perpendicular walls?

I think from a practical standpoint (and ignoring overhangs, since we don't have a plan to look at) it would be ok to terminate 4' beyond the more narrow building. But from a strict code standpoint, it would need to extend the full width of the wide building.

I know that doesn't really answer your question. Since the code has some allowances for vertical continuity, doesn't it lend a little credibility that the 4' would be ok in this case?

 

[RLGA]

Read Section 706.5.1 (2009 IBC). The fire wall only needs to extend to the exterior walls. Therefore, the fire wall is only required to extend the width of the narrower building, since the additional walls of the larger building on each side of the narrower building are exterior walls by IBC definition. The 2009 IBC Commentary provides an example of this exact condition on page 7-39.

 

[gbhammer]

However, the fire wall is also part of the wider building. The code says it must extend from exterior wall to exterior wall. So when looking at the wide building, wouldn't the fire wall have to extend from exterior wall to exterior wall? Can you just terminate a fire wall in the middle of a wall run, without it extending to the exterior perpendicular walls?

A fire wall can end at any point where it is no longer required, but you have to remember for it to be a fire wall it would have to stand alone for its required time even though the rest of the continued wall may fall. In effect you have two walls not reliant upon one another even though they appear to be one wall.

 

[texasbo]

A fire wall can end at any point where it is no longer required, but you have to remember for it to be a fire wall it would have to stand alone for its required time even though the rest of the continued wall may fall. In effect you have two walls not reliant upon one another even though they appear to be one wall.

Right; and that is the question posed by the OP: where is the fire wall allowed to end? RLGA's interpretation comports with my rambling analysis in post #7 above. Where would you say the fire wall could terminate?

 

[RLGA]

The point is well-made that the fire wall has to be structurally independent of the buildings on each side. If the fire wall was contiguous with the additional exterior walls, then the additional exterior walls would need to have the identical structural independence; however, the openings in the additional exterior walls would need only comply with the protection requirements for exterior walls and not for fire walls.

If the fire wall is not contiguous with the additional exterior walls, then the intersections with the exterior walls could comply with one of the exceptions to Section 706.5 (2009 IBC) as applicable, or extend the four feet beyond the walls of the narrower building and create a construction joint between the fire wall construction and the remaining exterior wall construction.