This is both a “Code Question” as well as a “even if Code allows it, is it wise” question. The plan is for Phase 2 of the house expansion (which could affect the design of Phase 1 which is why I’m asking NOW these questions) is for a basement that is going to have a floor joist/plywood floor, does it need to have a concrete “base” for the floor, or can it be like in an unfinished crawlspace, crushed stone on top of polyethylene sheets.   The walls of the basement would be precast concrete (I am eschewing using PWF as I have learned that they are not as reliable as they once were as the chemicals used in PT wood is not as reliable to prevent rot and other issues as well).  For a PWF basement, it was always a wood floor installed, so can the same be true for a concrete wall basement?  

The house is located in WNY.  The floor will be insulated.  This would save on costs of the wood walls for a 2nd Floor (studs, sheathing, siding, etc) and having a one story building is not as unsightly as have a 70′ wide 2 story building.   

So either the building will have a 4′ crawlspace with two stories, or an 8′ basement with one story.  

Thanks all for your help.

Ken L