Mass scan for 3d model.

I want to make a Spore-like building editor with ability to destroy it by separate part, and also I want to somehow create HP generator for it. To make it better and avoid some theoretical gameplay tricks, where player can put 100 sheets of iron in one, so that nobody could ever destroy his wall. I want to somehow scan a building for hollow places and create 3d array, so that HP will only generate from parts of building, where there are actually a mass: poligons, points, etc. When I could generate for every part its HP, according to HP of whole building. So in theoretical situation this 100 sheets will have HP as just one of them.

For now I have no idea, how to make this “scan”. Or, maybe there are a different smart ways to create this? Thanks!