# Type of Framing For a Platform



## fj80 (Sep 1, 2017)

2012 IBC

This is more of a construction question than code, but still some code issues, so...

I'm designing a restaurant inside an existing building. As best I can tell the existing building is Type 2B: The existing structure that I can see is all steel but not fire-protected.

The restaurant booths will be set on a platform one step up (say around 6") from the main floor level. (This is being done simply as a design choice, not based on any requirements or existing conditions.)

All the new walls will be metal stud and drywall, but I'm trying to decide what to frame the platform out of. Since the building is most likely 2B, I believe I cannot use wood and must use some sort of metal floor framing. Is this assumption correct? I must use metal and not wood?

Second issue: Since the floor framing members are sitting on a concrete slab floor their entire length, they aren't spanning any distance and don't really need to be as deep as most floor joists. The metal floor joist sizes I find online are deeper than I need. I only need them to be around 3-1/2" to 5-1/2" inches, to get the approximately 6" step I want. What are some appropriate framing products for this situation that meet code for a 2B building?


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## fj80 (Sep 1, 2017)

Also- Is it acceptable to use metal wall studs on their edge as floor framing when they're resting on the concrete slab their entire length, i.e. not spanning any opening? I'm guessing they may not have enough strength in that axis since they're designed to support loads in their normal vertical orientation in a wall.


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## steveray (Sep 1, 2017)

18 GA. steel studs? Should come in 3-5/8" and 5.5" You might look under Sleepers and such under 601 I believe....If you are not "spanning", you might get away with it...

They moved it to it's own floor section now:

SECTION 805
COMBUSTIBLE MATERIALS IN
TYPES I AND II CONSTRUCTION
805.1 Application. Combustible materials installed on or
embedded in floors of buildings of Type I or II construction
shall comply with Sections 805.1.1 through 805.1.3.
Exception: Stages and platforms constructed in accordance
with Sections 410.3 and 410.4, respectively.
805.1.1 Subfloor construction. Floor sleepers, bucks and
nailing blocks shall not be constructed of combustible materials,
unless the space between the fire-resistance-rated floor
assembly and the flooring is either solidly filled with noncombustible
materials or fireblocked in accordance with Section
718, and provided that such open spaces shall not extend
under or through permanent partitions or walls.
805.1.2 Wood finish flooring. Wood finish flooring is permitted
to be attached directly to the embedded or fireblocked
wood sleepers and shall be permitted where cemented
directly to the top surface of fire-resistance-rated floor assemblies
or directly to a wood subfloor attached to sleepers as
provided for in Section 805.1.1.


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## fj80 (Sep 1, 2017)

Thank you! So if you used wood sleepers and a plywood subfloor for the platform, what type of non-combustible material would one typically use to solidly fill the void between the sleepers?


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## steveray (Sep 1, 2017)

Mineral wool or fiberglass insulation work as fireblocking....Isn't it amazing that Toyota and Jeep guys can get along?


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## fj80 (Sep 1, 2017)

steveray said:


> Mineral wool or fiberglass insulation work as fireblocking....Isn't it amazing that Toyota and Jeep guys can get along?


Hahaha! It's because we're not talking about trucks. We've found our common ground- buildings!

So if I understand the code correctly- It is allowable to build the platform out of wood 2x- sleepers on the concrete slab on grade, fill the voids with mineral wool or fiberglass insulation, and put a plywood subfloor and wood finish flooring over the top?


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## Francis Vineyard (Sep 1, 2017)

fj80 said:


> Hahaha! It's because we're not talking about trucks. We've found our common ground- buildings!
> 
> So if I understand the code correctly- It is allowable to build the platform out of wood 2x- sleepers on the concrete slab on grade, fill the voids with mineral wool or fiberglass insulation, and put a plywood subfloor and wood finish flooring over the top?


Shouldn't it be glass fiber?


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## khsmith55 (Sep 1, 2017)

Another note, if the buildings sprinklered check with your FPE on the "limits" of concealed combustible construction.


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## fj80 (Sep 2, 2017)

Francis Vineyard said:


> Shouldn't it be glass fiber?


I believe that mineral wool has the better fire-resistance of the two...


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## fj80 (Sep 2, 2017)

khsmith55 said:


> Another note, if the buildings sprinklered check with your FPE on the "limits" of concealed combustible construction.


The building is not sprinklered, but good point for future projects. Thanks!


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## steveray (Sep 5, 2017)

A typical exemption for omitting sprinklers in NFPA 13 is filling the cavities as well.....


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