In this sentence (from [here](https://nhkeasier.com/story/2660/))

> このビルは２０階建てで、地下は２階まであります。

the building has 20 floors. Are there 2 basements (perhaps in addition to the
20 floors), or is it that floors up to (まで) the second one are underground
(which there are not in the photograph, it is rather a building on stilts)?
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2019-03-29T09:39:37.490
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question
nuances particle-まで
Why まで in this sentence?
First, まで can mean "even" or "so far as" with a nuance of the info being
surprising or unexpected. It's a bit like さえ in that regard.

Second, it helps to know that basements are unusual in Japan, even in larger
buildings.

Third, even if you don't know that Japanese buildings are counted from the
ground up, 地下 has a は topic marker after it. That は tells you the ２階 only
pertain to the 地下 and are independent of the other 20階.

Together, this gets you a 20-floor building that even has 2 levels underground
(for a total of 22 floors).
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2019-03-29T12:30:41.177
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* n階建て usually refers to the number of floors above the ground (including the first/ground floor).
  * In legal jargon, 階数 refers to the total number of floors including basement floors.

So this sentence usually means the building has 20 floors _above the ground_ ,
plus two basement floors, i.e., there are 22 floors/階数 in total. If you want
to be more specific, you can say 地上20階建て ("20 floors above the ground").

(～まである is a common way to say "to reach ～". It has no exclamatory tone.)
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answer