Type III-B construction

[georgia plans exam]

Table 601 (2012 IBC) requires the exterior bearing walls to be rated at 2-hours for type III-B construction.

Is the intent to protect the type III-B building from an adjacent structure, to protect the adjacent structure from the type III-B building, to protect the structural integrity of the Type III-B building itself or all three?

Thank you,

GPE

 

[Markmax33]

From the 2009 commentary - http://publicecodes.cyberregs.com/icod/ibc/2009f2cc/icod_ibc_2009f2cc_6_sec001.htm :

Bearing walls—exterior and interior. Exterior bearing walls are the outermost walls that enclose the structure and support any structural load other than their own weight. Their required fire-resistance rating is established by the higher of two fire-resistance ratings. The first component of determining the fire-resistance rating is based on the type of construction of the building. The second component of determining the fire-resistance rating is based on the exterior wall's fire separation distance in Table 602. Whichever of the two requires the higher fire-resistance rating will dictate the minimum required fire-resistance rating of the exterior wall.

I would say it's mostly #3 but the table 602 does include some consideration for the adjacent structures.

 

[georgia plans exam]

Thanks for your response. I was thinking #3 also but then I began to wonder.....why only the exterior bearing walls? If the intent is to protect the structual integrity of the building, why would not the interior bearing walls also require a 2-hour rating?

GPE

 

[cda]

sounds like protect it from the type of occupancy and possible fuel load the occupancy may have

and from neighboring buildings

 

[Codegeek]

I'm inclined to think it has to do with protecting adjacent buildings. Everything within the Type IIIB can be of any material permitted within the code, including wood. The primary application of this construction type is to the old manufacturing buildings. The exterior walls were always made of brick while the interior could be anything.

View attachment 956

View attachment 956

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[Builder Bob]

The old train of thought for ordinary construction was to allow a fire to take the building or origin while not affecting the adjacent buildings..... hence pockets and fire cuts....

This is an old hold over from days of past ------

 

[cda]

I'm inclined to think it has to do with protecting adjacent buildings. Everything within the Type IIIB can be of any material permitted within the code, including wood. The primary application of this construction type is to the old manufacturing buildings. The exterior walls were always made of brick while the interior could be anything. View attachment 2187

If you look at 602 the rating goes up as the occupancy hazard goes up

 

[Codegeek]

If you look at 602 the rating goes up as the occupancy hazard goes up

Thanks cda, I didn't look at 602. I'd say then it applies to all of the above in reference to the question.