R2 HighRise Type IB Construction

[jar546]

Can you lay down non-fire rated plywood over the concrete slab of a high-rise so they can install hardwood floors? I only see approval for wood sleepers in 805

 

[RLGA]

That's one of the problems with building codes: they cannot provide all of the possible prescriptive methods of accomplishing the same result.

The intent of Section 805 is to limit voids under combustible flooring. If a subfloor was adhered directly to the concrete floor, then I see that as being no different than a subfloor attached to sleepers constructed in accordance with Section 805.1.1.

 

[jar546]

That's one of the problems with building codes: they cannot provide all of the possible prescriptive methods of accomplishing the same result.

The intent of Section 805 is to limit voids under combustible flooring. If a subfloor was adhered directly to the concrete floor, then I see that as being no different than a subfloor attached to sleepers constructed in accordance with Section 805.1.1.

I agree with you because you can use sleepers but have to use blocking but plywood would eliminate blocking.

 

[steveray]

Directly applied? I'd say yes and agree with Ron....Void space is the concern with concealed combustibles...No air, no fire...

 

[Paul Sweet]

804.1 exempts wood flooring. I don't see any limit on the thickness of wood flooring, so the plywood could be considered part of the flooring. 805 only applies where you have voids, as RLGA and steveray pointed out..

 

[classicT]

804.1 exempts wood flooring. I don't see any limit on the thickness of wood flooring, so the plywood could be considered part of the flooring. 805 only applies where you have voids, as RLGA and steveray pointed out..

I agree with the principal of what you are saying, I just wouldn't go so far as to say plywood underlayment can be considered part of the flooring. Under that statement, it would appear that you'd accept plywood sheathing on bar-joists as a floor assembly because "the plywood could be considered part of the flooring".

What I'd say is that 805.1.1 permits the wood members (sleepers, bucks, and nailing blocks) for the attachment and support of floor finishes, so long as there is no concealed space wherein fire may propagate.

805.1.1 Subfloor Construction
Floor sleepers, bucks and nailing blocks shall not be constructed of combustible materials, unless the space between the fire-resistancerated 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.

 

[steveray]

If the plywood is spanning the structural framing it is structural....Methinks you won't find a finish flooring that will span 5'...And if you do I will still call BS....If you remove it do I fall to my death? If yes, it is structural....My litmus test

 

[Paul Sweet]

ClassicT, I should have said 'finish flooring".

 

[jar546]

If the plywood is spanning the structural framing it is structural....Methinks you won't find a finish flooring that will span 5'...And if you do I will still call BS....If you remove it do I fall to my death? If yes, it is structural....My litmus test

Instead of putting the plywood or finished wood flooring on sleepers, they are planning on attaching the plywood directly to the concrete slab of whatever story they are working on.

 

[steveray]

So, not structural so it meets construction type, so to common sense out a solution not spelled out in 602 or 3(?) i would liken it to very closely spaced sleepers.........What's the diff?