Porches ?

[loftus49]

How does one create a porch ... no walls just a platform and roof?

[harbinger]

I would wall it off as it were a regular room, then go to Room Creation mode, double-click inside the "room", then delete the walls I won't be using around the porch.
The nifty thing about doing it this way is that you can easily create simple columns by splitting and resizing the wall segments. Or you can lower the height of the wall if your porch will be surrounded by a stoop.