roof installation begins
The first roof materials, including its cladding or supporting understructure, are fixed during initial construction.
Installation of a structure's roof begins when the first materials belonging to the roof, including cladding and understructure, are affixed into place during the initial construction phase. This does not include commencement of work on a new roof for an existing structure, or any kind of roof renovation.
The first installed material can belong to the roof understructure, so the event can precede placement of the outer covering. Materials delivered to the site have not yet been affixed in place.
Roof renovation begins concerns work on an existing roof. This event concerns initial roof construction and has a separate installation endpoint.