What do you mean by the roof?

The roof of the building has been completed and reached the state of capping.

When the building is capped, it means that the main structure of the building has been completed, including the foundation, walls and floors of the building. After the roof is capped, construction workers can begin to decorate and decorate the interior and exterior of the house, such as installing doors and windows, decorating walls and floors, and installing water and electricity equipment.