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1 Hour roof ceiling assembly in existing building

imasayer

Member
Joined
Mar 29, 2013
Messages
4
Location
Billings
Good day folks,

Long time reader, first time poster so please forgive me if I am putting this in the wrong place or if this information has been covered before. Did a search but couldn't find anything.

I am currently working on a tenant improvement project in a 3 story building. The stairs were never rated. We are replacing the doors and the walls are cmu, so no issue there, but I am struggling with the roof/ceiling assembly. The problem is that I don't know what the roof assembly is between the steel deck and the single ply membrane. Every UL assembly I can find requires gyp or cement board over the the steel deck. Anyone aware of a 1-hour assembly that does not require this?

What I know about the assembly is: 3' steel trusses @ 60" O.C., 1 1/2" steel deck, some amount of some kind of insulation, and single ply membrane.

The building is 3- story, 34,000 sf, B & A-3 Occupancy (non-seperated)

Thank you for any help! (and for all the help I have found in the past!)
 
Question #1: Why do you need to know the roof assembly construction?

Question #2: What is the existing construction type?

Question #3: Is the total building area 34,000 sq. ft., or is that the floor area of the largest story?

Question #4: What percent of the story area is the Group A-3 occupancy?

As for finding out about the roof assembly, you can have a core sample taken by a roofing consultant/contractor or the manufacturer of the roofing membrane. If the roof is still within warranty, the roofing membrane manufacturer may have the details of the roof assembly in their records.
 
Question #1: Why do you need to know the roof assembly construction?

Question #2: What is the existing construction type?

Question #3: Is the total building area 34,000 sq. ft., or is that the floor area of the largest story?

Question #4: What percent of the story area is the Group A-3 occupancy?

As for finding out about the roof assembly, you can have a core sample taken by a roofing consultant/contractor or the manufacturer of the roofing membrane. If the roof is still within warranty, the roofing membrane manufacturer may have the details of the roof assembly in their records.
Hi RLGA,

Because all of the 1 hour roof/ceiling assemblies I find require gypsum board or cement board over the steel deck. Looking for help on this question specifically.

#2 - Type II-B construction. Sprinkled.
#3 - Total building - average 11,00- sf/floor
#4 - I don't remember the percentage - but I know it was less than 100 sf over the percentage to make it accessory to the B occupancy. The building is small enough that it didn't make it a huge difference do call it an "A".
 
Thank you!

I am rating the stair only.
But why are you rating the ceiling/roof assembly?

Shafts do not typically require enclosure at the top. See IBC Section 713.5, which directs you to 707.5.

707.5 Continuity
Fire barriers shall extend from the top of the foundation or floor/ceiling assembly below to the underside of the floor or roof sheathing, slab or deck above and shall be securely attached thereto. Such fire barriers shall be continuous through concealed space, such as the space above a suspended ceiling. Joints and voids at intersections shall comply with Sections 707.8 and 707.9.
Exceptions:

  1. Shaft enclosures shall be permitted to terminate at a top enclosure complying with Section 713.12.
  2. Interior exit stairway and ramp enclosures required by Section 1023 and exit access stairway and ramp enclosures required by Section 1019 shall be permitted to terminate at a top enclosure complying with Section 713.12.
 
But why are you rating the ceiling/roof assembly?

Shafts do not typically require enclosure at the top. See IBC Section 713.5, which directs you to 707.5.

707.5 Continuity
Fire barriers shall extend from the top of the foundation or floor/ceiling assembly below to the underside of the floor or roof sheathing, slab or deck above and shall be securely attached thereto. Such fire barriers shall be continuous through concealed space, such as the space above a suspended ceiling. Joints and voids at intersections shall comply with Sections 707.8 and 707.9.
Exceptions:

  1. Shaft enclosures shall be permitted to terminate at a top enclosure complying with Section 713.12.
  2. Interior exit stairway and ramp enclosures required by Section 1023 and exit access stairway and ramp enclosures required by Section 1019 shall be permitted to terminate at a top enclosure complying with Section 713.12.
You couldn't see it, but I smacked my forehead. I knew this.... just had the wrong thing in my head.

Thank you for waking me up gents!
 
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