renovation
The act of fixing up and improving an existing building.
Renovation means fixing up or improving a building or space, usually to make it more modern, functional, or attractive. When a family renovates their kitchen, they might replace old cabinets, install new countertops, and update the appliances while keeping the basic structure of the room the same.
Renovation is different from building something brand new. If you tear down an old house and build a new one from scratch, that's new construction. But if you take that same old house and update the bathrooms, repair the roof, refinish the floors, and repaint the walls, that's renovation. You're working with what's already there, breathing new life into it.
Schools often undergo renovation during summer breaks, when workers might repaint classrooms, replace worn carpet, or modernize the library. Historic buildings get carefully renovated to preserve their character while making them safer and more comfortable for modern use. A renovated baseball stadium might get new seats and better lighting but keep its classic facade.