Plywood over metal decking?

[Yankee Chronicler]

It is structural gyp board.

No, it's not. It's a Portland cement product.

Link to the brochure with rated floor-ceiling assemblies. None shown on M deck -- they're all on steel C-joists.

https://www.usg.com/content/dam/USG_Marketing_Communications/united_states/product_promotional_materials/finished_assets/fire-acoustics-manual-SCP100.pdf

 

[steveray]

I'd argue that the plywood is allowed as a floor finish and the floor likely does not need to be 1 hour rated....

 

[Yankee Chronicler]

I'd argue that the plywood is allowed as a floor finish and the floor likely does not need to be 1 hour rated....

What's the 1-hour rated floor-ceiling assembly, and the subfloor component of that?

I agree -- if the plywood is the "finished" floor, it is allowed. If it's the subfloor and part of the rated assembly, it's not allowed.

 

[bill1952]

What's the occupancy of the building?

 

[steveray]

What's the 1-hour rated floor-ceiling assembly, and the subfloor component of that?

I agree -- if the plywood is the "finished" floor, it is allowed. If it's the subfloor and part of the rated assembly, it's not allowed.

I'm arguing the floor/ ceiling does not need to be rated as I do not know that "utility rooms" need to be rated even though the OP does:

I know the utility rooms have to be 1 hour rated including the lid.

 

[classicT]

I'm arguing the floor/ ceiling does not need to be rated as I do not know that "utility rooms" need to be rated even though the OP does:

I'm not sure why they are required to be rated per the OP. Perhaps incidental use (Sec. 509).

 

[Yankee Chronicler]

I'm arguing the floor/ ceiling does not need to be rated as I do not know that "utility rooms" need to be rated even though the OP does:

The OP stated that the utility room requires a 1-hour rated enclosure. Unless he changes that, I don't see anything productive to be gained by making suggestions that don't incorporate that as a parameter.