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Most detailed definition I could find:

床下とは
建物の床の下。えん（縁）のした。

Picture from google:

enter image description here

Example:

その大雨で床下30センチまで水につかった。
The heavy rain flooded my house up to 30cm below the floorboards.

However, what I don't understand from the above is:

Does the water rise within 30cm distance of the wooden floorboards (upper limit) or 30cm above the cement floor (lower limit, like on the picture)? Does 床下 refer to the whole space? In any case, what exactly happens in the example sentence?

senshin
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user12127
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3 Answers3

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Upper limit.

Though 床下【ゆかした】 stands as a noun by itself, it literally means "under-floor". Therefore, 床下30センチ always means "-30cm from the floor level". 床 in this phrase is understood as the floorboards you live upon. If you want to tell you have 30cm deep water in the space between the base and the floorboards, you have to say 床下に30センチ (so that you grammatically treat 床下 as a noun).

Similarly, 床上【ゆかうえ】 is used for "above the floor level" as well.

Or more generally, there are lots of words with ～上/下 that means "(distance) above/below X".

  • 桁上【けたうえ】/桁下【けたした】 above/below the girder (see the pic)
  • 股上【またがみ】/股下【またした】 (of bottom wear) rise / below the crotch
  • 地上【ちじょう】/地下【ちか】 above/below ground
  • 氷点下【ひょうてんか】 below freezing (= minus degree Celsius)

enter image description here

EDIT

"床下 + number" is possibly open to two ways of interpretation (see the comments)... But at least I've found a J-E dictionary entry that says:

床下10センチまで水につかった
The flood waters rose to within ten centimeters of the floor of his house.

broccoli forest
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  • Hmm, now I am not so sure about what I wrote I was pretty sure in my answer…. – Tsuyoshi Ito Jan 05 '16 at 12:09
  • @TsuyoshiIto えっマジですかこれ…床下… – broccoli forest Jan 05 '16 at 12:18
  • 正直なところ、自信がなくなってきました。そもそも厳密さが要求される場面ではこんな言い方はしないのではないかという気も……。 – Tsuyoshi Ito Jan 05 '16 at 12:24
  • @TsuyoshiIto 確かに今ググってみましたが、「床下○○センチ浸水」とかあんまり出てこないですね…みんな大体「地盤から○○センチ浸水」といってるようです – broccoli forest Jan 05 '16 at 12:30
  • 床下の空間の高さがわからない状況で床から水面までの距離を言うのは不自然だと思います。 – h2so5 Jan 05 '16 at 12:31
  • あと「床下浸水○○センチ」というのは確かに＝浸水深だと思います – broccoli forest Jan 05 '16 at 12:32
  • @h2so5 確かに客観的な測定では不自然ですね。「あと何センチ上がったら床が浸かる（ところだった）！」っていう気持ちでないと出ないかもしれません。 – broccoli forest Jan 05 '16 at 12:34
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    「床下30センチまで水に浸かった」と書くと、「30センチの床下浸水」＝「地面から30センチ」をイメージします。でも「床下5センチまで水が来た」って書くと、「床から5センチ」と感じてしまう。面白いですね。 – marasai Jan 05 '16 at 12:35
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    @broccoliforest 床下が60センチもあれば「半分も浸水している！」ってなるんですけど、上の写真みたいに一般的には床下ってそんなに高くないので30センチも水面から離れているとあまり浸水していないように感じますね。 – h2so5 Jan 05 '16 at 12:46
  • @h2so5 現行建築基準法だと床下高は45cm以上だそうで、45cmを越えると床上浸水扱いなんだそうで。それを考えると大した高さじゃないみたいですね。浸水の経験がないのでわからないですが、床下に水が侵入すること自体は珍しくないんでしょうか。 – broccoli forest Jan 05 '16 at 12:54
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I am pretty sure that 床下30センチ in your sentence means 30 centimeters above the ground, with additional information that it is below the floor level. It does not mean 30 centimeters below the floor level (that is, the distance from the floor level was 30 centimeters), which would be 床の30センチ下.

床下 means the space under the floor, as in 床下に収納スペースがある家 (a house with an underfloor storage).

Note/Warning/Excuse. I was pretty sure when I posted this answer, but I am no longer sure. I admit that I could not find evidence that my interpretation was correct. broccoli forest’s answer proves that at least some people interpret it differently from what I wrote above. Maybe my interpretation is simply wrong, or maybe the sentence is ambiguous.

Tsuyoshi Ito
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I understand the sentence, “床下30センチまで水につかった” implies that the water below the floor came up to 30 centimeters high from the ground. I casted this question to several members of English speaking circle I'm with to monitor other's view. The answer was unanimously 'the height from the ground.' Reason? It’s easier to fathom the depth of water from the ground than measuring the length of gap between the crest and floor level by creeping into 'below-floor.'

Yoichi Oishi
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