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Fire Separation Distance - Double Wall

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Phil C

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Joined
Mar 10, 2022
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29
Location
Bath, Maine
Hello, would anyone be able to provide any feedback on this?

The project is in Maine IBC 2015 (for the most part), VB construction, 3-4 stories, We are exploring splitting 2 buildings on the same property. I am proposing to zig zag the new property line between the two. Nevertheless less some walls will need to be converted to 1 hour fire rating (protected on both sides) due to its proximity to this property line. As opposed to removing the siding and adding fire rated sheathing such as LP flame block and adding a rated gypsum wall board on the inside. What if we just built a typical fire rated wall just inside the exterior walls required to be rated? It could be a bearing wall in the case of a fire. It could be rated gypsum wall board on both sides. One concern is I would have no fire rating from the exterior at the floors.
 
Even with a shaft wall, you'd still have an issue at each floor wherein you couldn't have a continuous membrane nor a proper fire-resistive joint.

Can you put a structurally independent fire-wall between the two buildings? An 8-in masonry wall could perhaps be designed in a way such that it does not require lateral support from either existing building and would meet the fire resistive requirements.
 
What is the final fire separation distance between each building and the imaginary lot line?
 
Phil C said:
Hello, would anyone be able to provide any feedback on this?

The project is in Maine IBC 2015 (for the most part), VB construction, 3-4 stories, We are exploring splitting 2 buildings on the same property. I am proposing to zig zag the new property line between the two.
Click to expand...

How do you split a building?

Or are you really saying that you have two buildings on one parcel and you want to subdivide the parcel into two separate parcels?
 
classicT said:
Even with a shaft wall, you'd still have an issue at each floor wherein you couldn't have a continuous membrane nor a proper fire-resistive joint.

Can you put a structurally independent fire-wall between the two buildings? An 8-in masonry wall could perhaps be designed in a way such that it does not require lateral support from either existing building and would meet the fire resistive requirements.
Click to expand...
Thank you very much, I really liked this idea, but after thinking about and reading these, not liking it anymore. The current area that needs to be fire rated is not that big. Will probably remove the siding and install fire rated wall sheathing, also adding fire rated gypsum wall board on the other side. I believe UL has an assembly for this.
 
Phil C said:
2 buildings on one lot, we are proposing to subdivide
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Even if they were two buildings on the same lot, it is likely that FSD applied. Not sure what code they were built under, so I can't be 100% sure. But for your current code, they would have been considered part of the same building under IBC 503.1.2 or needed FSD per Table 602.

2015 IBC - 503.1.2 Buildings on Same Lot​

Two or more buildings on the same lot shall be regulated as separate buildings or shall be considered as portions of one building where the building height, number of stories of each building and the aggregate building area of the buildings are within the limitations specified in Sections 504 and 506. The provisions of this code applicable to the aggregate building shall be applicable to each building.
 
Phil C said:
2 buildings on one lot, we are proposing to subdivide
Click to expand...

I'm not seeing two buildings in your partial plan, I see what appears to be one large building. That said, your partial plan appears to put a ramp on one property and the deck the ramp serves on the other property. The deck itself will end up split, with part on each property. Does that deck serve both buildings? How will access from one property to the other be controlled?

Where are the exit doors? Since a property owner has no control over what another property owner may do, egress is typically considered to be from your building to a street or public way BY ROUTES ENTIRELY ON YOUR PROPERTY unless there are easements established to maintain the viability of paths of exit discharge in perpetuity.
 
classicT said:
Even if they were two buildings on the same lot, it is likely that FSD applied. Not sure what code they were built under, so I can't be 100% sure. But for your current code, they would have been considered part of the same building under IBC 503.1.2 or needed FSD per Table 602.

2015 IBC - 503.1.2 Buildings on Same Lot​

Two or more buildings on the same lot shall be regulated as separate buildings or shall be considered as portions of one building where the building height, number of stories of each building and the aggregate building area of the buildings are within the limitations specified in Sections 504 and 506. The provisions of this code applicable to the aggregate building shall be applicable to each building.
Click to expand...
Sorry, it is two buildings on one lot. The client is considering buying one of the buildings only and creating a new property line between the two. The buildings are shown in a diagonal hatch. Thanks!
 
Yankee Chronicler said:
I'm not seeing two buildings in your partial plan, I see what appears to be one large building. That said, your partial plan appears to put a ramp on one property and the deck the ramp serves on the other property. The deck itself will end up split, with part on each property. Does that deck serve both buildings? How will access from one property to the other be controlled?

Where are the exit doors? Since a property owner has no control over what another property owner may do, egress is typically considered to be from your building to a street or public way BY ROUTES ENTIRELY ON YOUR PROPERTY unless there are easements established to maintain the viability of paths of exit discharge in perpetuity.
Click to expand...
Hello sorry, the buildings are indicated by diagonal hatch. The existing deck/ramp is indicated by horizonal hatch. The deck does serve both buildings. We are waiting on the code enforcement officers feedback on the deck. I think we are ok with the exit doors. Thanks!
 
Phil C said:
Sorry, it is two buildings on one lot. The client is considering buying one of the buildings only and creating a new property line between the two. The buildings are shown in a diagonal hatch. Thanks!
Click to expand...
Understand that. But have you reviewed the original permit drawings to see how they handled the two buildings originally? They likely (depending on legacy code) had to either treat as one building, or establish an imaginary property line and comply with the FSD requirements.
 
classicT said:
Understand that. But have you reviewed the original permit drawings to see how they handled the two buildings originally? They likely (depending on legacy code) had to either treat as one building, or establish an imaginary property line and comply with the FSD requirements.
Click to expand...
Thanks that is a good point, I will look into that.
 
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