Platform or stage with stairs

I don't know if this is a modding request or not. Or if it will be possible  to make. But I want to ask. I want to build a platform on the second floor and add stairs to it. I tried half walls and you can't add floors on top of them. I want to do a living room one the platform so it looks a little more realistic. And I think it would be cool. Even if it's an object that you can add stair to.