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)
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word-choice nuances definitions
How to tell whether a building is マンション or アパート
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!
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One other distinction I've encountered in translating real estate-related
materials is that アパート generally refers to smaller buildings with multiple
units, but one owner for the whole building, whereas マンション generally refers to
larger buildings with multiple units, where each unit might be owned
individually. In this case, the difference between an アパート vs. a マンション is not
too dissimilar from the distinction in English between an "apartment" and a
"condominium".
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2018-04-11T18:08:50.010
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Yes, I had this issue clarified today by a native Japanese speaker. If you own
a condo, you should call it “マンション” but if you are renting an apartment in a
large building, that is an “アパート.”
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