Fire rating for concrete deck?


Working on an existing renovation project in NYC that requires a 1-hr fire rating between occupancies. There is an existing 5 1/2" concrete slab between the floors requiring the separation - can't seem to find in code whether this might be an acceptable separation as most of the data I'm seeing seems to show we should be above 1 hr with that thickness of concrete.  Would love to keep the ceilings exposed if possible.

Anyone have any experience with this?

Oct 12, 18 2:46 am
Non Sequitur
What does your architect think?
Oct 12, 18 6:05 am

Look through the UL material for a similar assembly.  5 1/2" of concrete is certainly going to be good for one-hour if two pieces of 5/8" drywall are.

Oct 12, 18 8:07 am

Do you have drawings for the original building? the only thing that can foil your plans is if the steel is or was designed to be too close to the edge of the slab.  Otherwise the UL listings is a commonly accepted means of determining the fire resistance ratting of an assembly provided you know the design of the slab.

Over and OUT

Peter N

Oct 12, 18 8:26 am

Look at NYC Building Code Section 720. More precisely, TABLE 720.1(3)

Oct 12, 18 8:26 am

Zbig is correct.  Spent lots of time back in the day pouring through UL and searching the web for this info, before stumbling across 720 (where were you then Zbig?)

Oct 12, 18 1:45 pm
t a z

There is no UL listing for a poured in place concrete slab, only slab on metal deck.

State and municipal building codes throughout the country regulate the fire resistance of the various elements and assemblies comprising a building structure. Structural frames (columns and beams), floor and roof systems, and load bearing walls must be able to withstand the stresses and strains imposed by fully developed fires and carry their own dead loads and superimposed loads without collapse for the specified duration. The 2006 International Building Code (IBC) (1) contains prescriptive requirements for building elements in Section 720. This section contains tables describing various assemblies of building materials and finishes that meet specific fire endurance ratings. The tables in the 2006 IBC are compatible with the tables in ACI 216.1 except for the provisions for the use of high strength concrete columns found in ACI 216.1-07. 

Oct 12, 18 2:13 pm
t a z

P.S. For existing concrete structures you need to know concrete type and cover thickness.


... yeah... what does your architect think?

Oct 12, 18 4:25 pm

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