3. Frame construction

Traditional framing is made up of systems that transfer loads to fixed points, evenly spaced in two flat directions called "span" and "bay" (or center-to-center distance).

Most of the roofs on today's and older buildings consist of flat surfaces arranged in simple combinations: horizontal slabs, gable roofs, pitched roofs and so on.

The roof structure is generally made up of a superimposition of different wooden or steel parts:

• trusses, supporting structure ;

• purlins, supported on the truss ;

• rafters, nailed to purlins ;

• battens or battens for roofing support.

As seen in §