併設
へいせつ joint establishment (esp. schools of different levels or different courses of study); establishment as an annex (e.g. of a school)
Why it means this
併 (together) + 設 (establish) — setting something up as an attached facility — a shop with a café, a school with a nursery (保育園を併設する).
Breakdown
Each character links to its full entry — origin story, stroke order, and readings.