This is a simple procedural building generator I put together recently whilst getting to grips with Houdini. The building dimensions are all parametrised, as is the roof slope angle, the type of main doors and whether external windows and access doors are present. The width of the main door can be tweaked independently of the building width. The access door and windows cut through the volume of the walls so as to function correctly. I'm also assigning appropriate materials to the resulting surface.
Its relatively simple at the moment but my intention is to take this further and potentially package it up as a Houdini Digital Asset that can be tweaked live in the Unreal Editor via the Houdini Engine plugin.