Several of the houses in Twinbrooks are like this. They used a special building tool to create them. Press CNTRL-SHIFT-C to bring up console. On console, type in "placefriezes on" (without the quotes). This changes the foundation tool in build mode to place friezes instead - basically just like the foundation, except placed on top of walls instead of on the ground. While it's turned on, you can't place foundations on the ground though, you have to turn it back off first (with "placefriezes off"). If you forget how to spell it in the game, you can type "help" in the console to see it listed.