also: かいま
noun
space between floors; inter-story space
Architectural term referring to the void or gap between the structural floors of a building, often housing mechanical systems or providing insulation.
このビルの階間には配管が通っている。
Pipes run through the space between the floors of this building.
階間の断熱材が老朽化している。
The insulation in the inter-story space has deteriorated.
Compound of 階 (kai, 'floor, story') and 間 (kan, 'space, interval'). The reading かいま is a less common kun'yomi variant.