Finished basement wall - Double top plate acts as fire blocking

[Tbcf]

Hello,

I want to frame a section of wall at perimeter of basement. Per code, the untreated stud cannot touch concrete wall, so I plan to put the studs 1 inch away from basement concrete wall. Also per code, fire blocking is required for that 1 inch gap.

My plan is: put a treated 2x4 that is parallel to and touches concrete wall as 1st top plate. Then put 2nd untreated 2x4 top plate 1 in away from concrete wall. It means the 2 plates overlap only 2.5 in.

Does my plan satisfy both structural requirements for wall as well as fire blocking requirement?

Or should I replace treated 2x4 by 2x6? Cost is one issue but I am afraid it will interfere with other pipes.

If it is ok to use 2x4, how should I nail them considering that the two plates overlap only 2.5 in?

Thanks.

 

[Mr. Inspector]

Nonstructural walls only need one top plate. No openings at all allowed between wall and ceiling

 

[steveray]

Can you put a rip of drywall on the ceiling before you frame the wall? That works nicely.....