The trusses are then trucked to the site, where they are lifted into place with a crane. Truss fabrication has made roof construction more affordable than it used to be, but it has also made some of the most functional roof forms of the past much less functional. There's all that space up there. A truss roof compared to a roof framed with rafters. An attic truss.
Attic trusses create a cavity between the webs for a room.
The economy of the prefabricated truss comes in large part from its ability to minimize bearing walls by transferring loads to the outside walls of the house. Unfortunately, these webs make the area within the roof unusable as living space. There is a partial solution to this problem. But they are more expensive than standard trusses, and they still don't provide as much interior living space as their hand-framed counterpart. So most houses built today don't have the old roof space available for living purposes.