How to tell whether a building is マンション or アパート


Given a building, how to classify it as マンション or アパート?

Non-subjective set of criteria preferred.  
In particular, if there is any legal definition of these terms that would be
the best.

I used to think that the difference was subjective, but apparently it is not,
as this bank asks its customers to declare formally whether they live in a
マンション or アパート (among other options):

![Manshon/mansion or Apāto/apartment](https://i.stack.imgur.com/Paepo.png)




One way to distinguish is to look at the **materials** supporting the
building's structure:

  * Light structure with either: 
    * [Timber](https://en.wikipedia.org/wiki/Timber_framing#Japanese)
    * [Prefabricated](https://en.wikipedia.org/wiki/Prefabricated_building)
    * Light steel beams

... is often アパート.

  * Heavy structure with either: 
    * Heavy steel beams
    * [Reinforced concrete](https://en.wikipedia.org/wiki/Reinforced_concrete)
    * Steel framed reinforced concrete

... is often マンション.

As pointed out by @Chocolate, <http://house-on.com/onepoint01.html> adds a
`中高層（3階以上）` (=at least 3 floors) condition for being a マンション.

Better/other criteria welcome!

