We recently purchased a house that was built in the 1930's. The 2nd floor has never been framed out. There is some rough plumbing done with the thought of being finished. The whole house is brick. Every 4 feet there is the face of 2x10 set into the brick flush to the floor as if they were going to attach trim to.
My question is do I fur out 2x4 on the exterior walls? Do I insulate the exterior walls with foam board and add insulation between studs? Do I allow an air gap between brick and just frame around brick walls? Do I use treated wood on the exterior? I would like to add electrical and in one portion the sink and shower may be against exterior wall so then do I use 2x6's? I am not sure if even need to insulate the exterior.
That was an old house and since there is no picture, according to your description, it seems the bricks looks like a wall in a castle. Maybe if possbile keep the brick wall as it is cause it may look great just few restoration on it.