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.  For example, old houses such as a Cape with a 10-in-12 roof or a French Colonial with a 12-in-12 roof can accommodate living space in the attic.  There's all that space up there.Why not live in it? 

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. Trusses do this with a multitude of web members, the diagonal braces that connect the chords of the truss together.

Unfortunately, these webs make the area within the roof unusable as living space.  There is a partial solution to this problem.  You can build the roof with attic-storage trusses, which have webs configured to keep a portion of the attic open. 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.

The paradox of truss-built roofs.

There is a nostalgia for the old roof forms, such as the bungalow or Cape, that say "I am a house" so clearly.  Many people love the look of such a home, with its dormers and its cottage charm.  Others like the feel of the rooms created within, with their cozy sloped ceilings, window alcoves, and nooks and crannies.  But sadly, the economical roof-construction techniques of today have actually made these economical houses of yesterday more expensive to build than their standard, two-story, truss-roofed offspring.
This is one of the reasons that houses today look bigger.  The roof typically sits above all the living space, rather than incorporating some of it.  In an attempt to mimic older house forms, you will often see new homes with these same roof shapes and dormers, but when you get inside, you discover that the dormers are just there for show and aren't accessible from anywhere.  Because the roof contains no living space, the footprint of the house has to increase to accommodate the same square footage on the main level.  As a result, the house that was supposed to look like a cottage often turns into a much bigger, more rambling, ill-proportioned house.

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