# Multiple buildings on one site and fire separation



## goaneer (Feb 28, 2013)

I have two buildings on one site.

The main building is 65000 square feet two stories Type II B.

The second building is U occupancy - 1000 square feet. Also Type II B.

Scenario A- Combining both under one building. This eliminates the fire separation requirement between the two buildings.

The combined square footage after considering the frontage addition falls under the allowable total for the B occupancy structure. The code does not explicitly state that the total allowable should be based on the more restrictive occupancy. Would U be considered the more restrictive occupancy?

Scenario B - If we consider them as separate buildings then the fire separation code requirements do apply.

So I draw an imaginary line between these two buildings. I place the line on the exterior wall of the main Type IIB building. This wall is concrete with a four hour rating.

Now if the U occupancy building is less than 5' from the imaginary line then it needs to be 1 hour rated and 0 hour rated if 10'.

I want to confirm that BOTH BUILDINGS NEED to adhere to the fire separation requirements.


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## north star (Feb 28, 2013)

*$ $ $*

goaneer,

*1st,* ...Welcome to The Building Codes Forum! 

*2nd,* ...what codes are you using, and what are the Occ. Groups

involved with the 65,000 sq. ft. bldg.?

Thanks!

*$ $ $*


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## steveray (Feb 28, 2013)

Mixed use unsep goes with the most restrictive which for some reason would be the U.....and would be very Area restrictive.....it could be incidental maybe or it looks like a one hr rating.....


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## fatboy (Feb 28, 2013)

Yeah, need a bit more info.

Welcome to the forum, goaneer


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## goaneer (Feb 28, 2013)

Appreciate the welcome

Sorry I thought I wrote.

Looking at CBC 503.1.2 for definition

The main building is 65,000 square feet  B occupancy.

The other building is U occupancy.

So now I understand if both structures had the same occupany and were combined as one structure the buildings could be closer eliminating the fire seperation requirement.

Now with mixed occupancies B and U if I have to follow U then I cannot combine as the square footage is so less. This means the fire seperation will kick in and if the U occupancy structure is less than 5' the U structure needs to be fire rated.

Am I thinking correctly or am I missing something?


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## steveray (Feb 28, 2013)

What do they use the U for?

Maybe look at 302.2 for accessory use.....302.2 Accessory use areas.

A fire barrier shall be required to separate accessory use areas classified as Group H in accordance with Section 302.3.2, and incidental use areas in accordance with Section 302.1.1. Any other accessory use area shall not be required to be separated by a fire barrier provided the accessory use area occupies an area not more than 10 percent of the area of the story in which it is located and does not exceed the tabular values in Table 503 for the allowable height or area for such use.


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## mtlogcabin (Feb 28, 2013)

Are you sure it is a "U" occupancy? Can it be classified under something else say an "S"? If so would 507.4 help out if the CBC has something similar


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## steveray (Feb 28, 2013)

If the U can be an S....the H&A requirements of 503 are alot more giving and closer to the B


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## goaneer (Feb 28, 2013)

It is a shed - with roof and four posts type of structure. So unfortunately is U occupancy.

So looks like the fire seperation will kick in.

So the main building exterior wall is concrete four hour rated. If I placed the imaginary line on the exterior line and have the shed less than 5' away from the imaginary line then the shed needs to be fire rated. 10' away we are good.

Please correct me otherwise.

Thank you folks for all your feedback.


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## north star (Feb 28, 2013)

*+ + +*





> "It is a shed - with roof and four posts type of structure. So unfortunately is U occupancy."


Not an "open air" Storage structure?    Nothing in the "U" Occ. Group

requires walls.

*+ + +*


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## goaneer (Feb 28, 2013)

Actually it is a canopy which has no walls but only a roof on four posts. The reason I said Shed because it is the closest I could think of in the U category.


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## north star (Feb 28, 2013)

*( + )*

As mentioned already, ...the "S" Occ. Group designation will be

a more giving / less costly application, ...if it is just a matter

of wordplay / semantics as how to designate & design.

Out of curiosity, what is the shed / structure being used, or

will be used for?

Thanks!

Also, ...might I encourage you to join this Forum with a paid

membership!.........Nothing like having that "Sawhorsie"

designation to tell your colleagues about!      Besides, this

Forum is THE  BEST  on the internet.

*( * )*


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## mtlogcabin (Feb 28, 2013)

> Actually it is a canopy which has no walls but only a roof on four posts


With no wall how does it comply with Table 705.8?

Look at 705.8.1 exception 2. If all you have is a structural frame then I believe 10 ft is the minimum fire separation distance you can be.


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## goaneer (Feb 28, 2013)

north star said:
			
		

> *( + )*As mentioned already, ...the "S" Occ. Group designation will be
> 
> a more giving / less costly application, ...if it is just a matter
> 
> ...


out of curiosity what does a paid membership enable more than what I have learned today?


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## mtlogcabin (Feb 28, 2013)

goaneer said:
			
		

> out of curiosity what does a paid membership enable more than what I have learned today?


Click on the link

http://www.thebuildingcodeforum.com/forum/website-discussion/9677-difference-between-sawhorse-registered-member.html


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## goaneer (Feb 28, 2013)

mtlogcabin said:
			
		

> With no wall how does it comply with Table 705.8?Look at 705.8.1 exception 2. If all you have is a structural frame then I believe 10 ft is the minimum fire separation distance you can be.


One of the building plan checker said we can assume an imaginary wall. So if the columns and roof are rated then one could assume the structure to be rated.

But now you are right per Table 705.8 this imaginary wall can be considered entirely open.

Then we need to be atleast 20' feet away with sprinklers and if we are 30' away there is no limit and nothing is required.

Thank you


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