wide, large
宏 centers on spaciousness and breadth: something wide, large, or expansive in scope.
宏 combines 宀 (roof) with 厷, which likely contributes the sound and may suggest something broad or extended under a roof.
Under a wide roof 宀, the space 厷 stretches out broadly, like a large hall.
For コウ, imagine a wide, open courtyard (こうてい) under the roof: こう -> コウ, and the space feels large and expansive.