The drainage system to the east suggests that this wall might have been an exterior wall of the structure. The large tiles abutting the wall to the east tilt away from the wall towards the sewer drain. The section of the wall below the bricks is much less presentable/finished that the opus mixtum above, which suggests that the original floor level aligned with the bottom of the brick section (i.e. above the foundation).
NS wall on eastern side of F south