I think it depends on what the additional buildings will be--will they be living spaces? A cafeteria? It's hard to say without knowing what the buildings will be. If actual "dwellings" (as defined by HMDA) are being constructed, i would call that a purchase. If the buildings being built are just 'support' buildings for the facility, it sounds more like "improving the real property on which the dwelling sits"--home improvement.
I'm fixin' to fix that.