I have a rather basic question that’s getting the best of me. I have just finished insulating my exterior walls in my basement using poly iso with a 2×4 wall interior to that. The house was built in 1938 located in Minneapolis.

I have an interior concrete block wall that basically divides my basement in half (sometimes called a strip footing which supports the first floor load). Considering this is an internal wall I was planning on simply installing 2×4’s flats so that the 3.5″ side is directly against this interior block wall. I have apprx a 11ft span then and 9ft span with an opening in between and would space the 2×4’s 16″ oc and finish with .50 drywall.

My questions is do I actually need to use a 2×2 top and bottom plate, in this application. Or would the vertical 2×4’s laid flat every 16″oc suffice? Ceiling is finished with sheetrock. The only thing reason I could think of using a top and bottom plate would be for fireblocking.