# Occupancy Separation - B & U - Fire-Resistive Construction



## Alias (May 10, 2013)

Okay, if this isn't the right spot please move.

I have a 3000 sq. ft. office building with and attached 800 sq. ft. carport.  Roof pitch is 11/2:12.

I met with the contractor about the carport and its' fire-resistive construction.  Plan details show 5/8" plywood, 2 layers 5/8" gypsum, and a 3 coat layer of plaster attached to the bottom chords of the trusses.  Argument between the engineer and the contractor is over the fire-resistive rating of a 3 coat plaster application.  Contractor thinks plaster is enough, engineer says no, gypsum board must be installed and then covered with plaster.

1991 UBC Table 43-B lists the plaster application and lists it as acceptable.

Questions - What is the fire-resistive rating for a 3 coat - ground, scratch, & finish - 7/8" plaster finish?

                Would this application meet the 1 hour rating?

                Are the gypsum and plywood a necessity to achieve 1 hr. fire rating?

One final question - Same carport/office building.  Carport shows no fire blocking above bottom chord of carport to bottom of the roof deck of office building.  Office building wall is wood and interior has dropped ceiling.  Would you require a 1 hr. separation between occupancies?

Thanks,

Sue  :cowboy


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## mark handler (May 10, 2013)

VERTICAL CONSTRUCTION-- 3 coat is one hour

HORIZONTAL CONSTRUCTION--- 3 coat is onehalf hour,  you need to add 5/8" gyp behind it

You need fire and draft stops


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## Alias (May 11, 2013)

Mark,

Thanks!  Contractor is adding fire and draft stops even though engineer swears it's not needed.  Main bone of contention between contractor and engineer is the horizontal assembly for the carport.  Do you have a code section to cite for the plaster?  I found a citation in the '91 UBC.

Sue


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## cda (May 11, 2013)

Might check through this section

Chapter 7 - Fire and Smoke Protection Features

722


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## mark handler (May 11, 2013)

Start with 2010 CBC Section 712 Horizontal Assemblies

To Comply With That Section the engineer or contractor needs to provide a assembly per Table 720.1 (3) Minimum Protection For Floor And Roof Systems or the Generic fire-resistance ratings (those not designated as PROPRIETARY* in the listing) in the GA 600 Fire resistive manual, or a UL design number

Or if the engineer can per 721.6 Wood assemblies. Use the calculations and procedures by which the fire-resistance ratings of wood assemblies are established by calculations, using Table 721.6.2(1) Time Assigned To Wallboard Membranes.


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## mark handler (May 11, 2013)

717.1 General. Fireblocking and draftstopping shall be installed in combustible concealed locations....

717.2 Fireblocking. In combustible construction, fireblocking shall be installed to cut off concealed draft openings (both vertical and horizontal) and shall form an effective barrier between  floors, between a top story and a roof or attic space.

717.2.2 Concealed waH spaces. Fireblocking shall be provided in concealed spaces of stud walls and partitions, including furred spaces, and parallel rows of studs or staggered studs, as follows: 1. Vertically at the ceiling and floor levels....

717.2.3 Connections between horizontal and vertical spaces. Fireblocking shall be provided at interconnections between concealed vertical stud wall or partition spaces and concealed horizontal spaces created by an assembly of floor joists or trusses, and between concealed vertical and horizontal spaces such as occur at soffits, drop ceilings, cove ceilings and similar locations.

And many more locations.....

There are exceptions, but they need to show you why they qualify for the exceptions, not you provide them the exceptions


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## Oldfieldguy (May 12, 2013)

I'm confused. Is this new or existing construction. I am somewhat sure that no fire-resistive separation is required between a Group B and Group U. The original poster mentioned the 1991 UBC. That requires me to walk to my archive library, which is shed in the backyard.


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## mark handler (May 12, 2013)

Oldfieldguy said:
			
		

> I am somewhat sure that no fire-resistive separation is required between a Group B and Group U. .


You might want to relook at IBC 2009 table508.4


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## Alias (May 13, 2013)

Oldfieldguy said:
			
		

> I'm confused. Is this new or existing construction. I am somewhat sure that no fire-resistive separation is required between a Group B and Group U. The original poster mentioned the 1991 UBC. That requires me to walk to my archive library, which is shed in the backyard.


Sorry for the confusion.  Contractor mentioned '91 UBC and I found the info there.  What he needed was a code sections from 2010 CBC for the horizontal assembly.

Sue


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## Alias (May 13, 2013)

mark handler said:
			
		

> Start with 2010 CBC Section 712 Horizontal Assemblies To Comply With That Section the engineer or contractor needs to provide a assembly per Table 720.1 (3) Minimum Protection For Floor And Roof Systems or the Generic fire-resistance ratings (those not designated as PROPRIETARY* in the listing) in the GA 600 Fire resistive manual, or a UL design number
> 
> Or if the engineer can per 721.6 Wood assemblies. Use the calculations and procedures by which the fire-resistance ratings of wood assemblies are established by calculations, using Table 721.6.2(1) Time Assigned To Wallboard Membranes.


Mark -

Thank you!

Contractor is from out of town and had questions/comments.  He will be providing 1 hr. protection to the top of wall between occupancies and draft stopping even though it is not on the plans.  Nice to hear a contractor take pride in the craftmanship.

I have invited him to join the Forum.

Sue


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