crumbling

describes a building that is old and falling into pieces

崩れかけた漆喰

describes plaster on a wall or ceiling that is breaking and falling off

崩れかけた遺跡

often used to emphasize the state of decay of an ancient structure

古代の建造物の崩壊状態を強調するためによく使われる

崩れかけた共同住宅

describes a poorly maintained apartment building that is falling apart

老朽化や放置により崩れかけている共同住宅。