From shape to solid

Question

Hello! 
 Is there a possibility to make a one solid from several shapes which probably make closed object? The example picture is below: 
 
 I've tried "Stitch Surfaces", converting to surfaces, "Union Feature", "Unite Solids", "Create Region"... Nothing helped, maybe I was doing it not exacly how I should. What is more interesting - I managed to convert similar object via "Stitch". But it is only one exception. The rest of the buildings is not so easy. Any ideas? I would be very grateful if you could help me.

Ron Jones · Answer

Hi Piotrass, 
 You could try using Extrude Mesh Volume . Here is an video example I made using roof surfaces and a foundation shape similar to those in your image. All items are extruded to the same elevation. This created a single mesh volume from the items extruded.

Ron Jones · Answer

If you follow the method I suggested you end up with a "water tight" mesh volume. This can then be converted to a smart solid via Convert to Solid . You can also simplify the mesh first with the Cleanup Mesh tool.