In the previous post I talked about the roof cutoff properties. The same mansard roof from that example can be made using the shape editing tools and are available when you select a flat roof (must be flat). These tools were introduced more recently (Pleistocene) and represented an initial foray into some new manipulation tools. It doesn't enable super sexy curvy like the 2010 concept modeling tools can but something great for roofs and floors with drains. Using these one can also create most roof shapes including some interesting saddle shapes.
Below are the basic steps for the Mansard:
Click the image below for a video of the complete process:
BTW These 1st generation tools can also model 1st generation stealth aircraft like the F117.
Now that the 2010 conceptual modeling tools are out I need to try modeling the second generation F22 before Zach over at Buildz beats me too it.