Is it possible to design a building as its own model?

I’m not much of a designer myself, but I’m seeing that most things seem to suggest building structures of BSP objects.
I’m also seeing that people are saying that StaticMeshes offer better performance than just using BSP for design, so I suppose my question should be is it desirable to design a structure in a modelling program then import it into UE4?

Yes, it is preferable to make the model in a 3D program. If budget is an issue Blender3D is free and there are plenty of tutorials for it.

Also. For something like a building, if it is just a set piece that is viewed from the outside it could just be one object, but if you intend to go into it, it should be separate pieces. If you make the components separately and import them individually and assemble them in UE4 you can reuse them as well.

You can use static mesh instancing for the duplicate parts.

Okay, that makes sense, and yeah. I get that it’s a necessity with how light mapping works and everything.

I just can’t understand why I’d want to use BSP’s over models as a single person working on a project. I’m sure there’s some utility I’m losing out on, but I just can’t wrap my mind around it.

Use BSP’s sparingly and more or less to simply map out your initial level design. You want as few BSP’s as possible in your finished project, replacing them with static meshes.

Like said. BSP’s are good for testing out the space. It’s called blocking out a level. But it’s just for testing, after you get the space how you like it you replace the BSP’s with meshes.