Building Interiors

So today I learnt how to create building interiors, first I used a simple 3D rectangle and turned it into an editable mesh. I then began extrude inside to create rooms, Oh and to see what I was doing I cut the top of my rectangle by deleting the poly's.

I wanted to create a more complex structure to test my skills, so I decided to create two floors but I found that creating stairs was harder than I thought. To overcome that problem I duplicated the shape to get the right measurements and decided to create two floors separately the stairs were a lot easier when you have something to compare against.

This is a render of how I progressed, but I forgot to flip the normals so you can see through it.