First, a great way to find out what objects are called, is to load into a place in the game that you know uses them, and start double clicking them and reading what their Base ID's are.
As for exterior houses? What kind of houses do you want? A cabin, like a village home, or a large house like in Whiterun or Riften? Let me load up the ol' (Brand new) CK here...
Ah, if you go to the object window, look in World Objects> Static> Architecture> Farmhouse. That has a lot of house type stuff in it. Other than that, poke around under Architecture and you should find what you want.
