Procedural building from spline...help

Hello everyone!
I’m working an actor that builds builidings from a Spline. The general idea is to make different shape buildings form a closed spline. Once you draw the spline the wall, the windows and the doors are set in place but I’m having a problem. I don’t know how to make a gable roof out of the very same spline. I want to recreated an old city so I don’t have the GIS system to use the CityEngine but I do have an AutoCAD drawing with shapes of the buildings so I asume the spline tool is the best thing to use.

Any ideas? or Anything that already exists that could do the very same thing?

Sounds like a job for Houdini