Any tips on how to create/design a multi-floored level?

Hi! So basically, I’m working on a free-roam simulation which is basically just traversing throughout my school. My school has 4 floors on the main building sight and has different sectors or pavilions that are connected to the ground floor of the main sight. I’m quite new at game design as well as UE4(few months experiment) and this is my first solo large scale project so I want to get some basic level design tips before I get started. So far, I have the basic construction models (walls, doors, ceilings, floors, stairs, etc.) as well as a replicated map of the school which I plan to use as reference. I was thinking of possibly creating different maps and dividing the school up per floor or section or just create all flat floors and simulate a teleportation when moving between floors on the stairs. I’m only thinking of how I’ll do this on precedent of my knowledge and like I said, I only a grain of salts worth about anything game design and UE4 related. I have no idea if this is the way to begin the creation of a full scale building in Unreal and I REALLY appreciate all tips, comments, or criticism. Thanks so much!