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Roof trusses

Span (truss span)

The span of a truss is the distance it covers between its supports, normally measured from the outside of one bearing wall to the outside of the other.

Also known as span, truss span, overall span, clear span, span length

Span is the first figure in any truss design, together with pitch and loads. It decides the truss type, member sizes and web pattern: short spans suit simple king post trusses, while longer spans need fink, fan or girder arrangements.

Truss makers usually quote the overall span (out to out of the bearings). The clear span, between the inside faces of the walls, is what gives the free room width below.

Apex (ridge) Nail plate Top chord Web Bottom chord Heel Overhang Span
The parts of a typical fink (W) roof truss. Every joint is held by a nail plate.
Related terms
Truss typesRoof trusses come in many shapes, such as fink, mono, attic, scissor and girder trusses, each suited to a different roof form, span or use of the roof space. Fink trussA fink truss is the standard pitched roof truss, with internal webs arranged in a W; it is the most widely used truss type for houses. Girder trussA girder truss is a strengthened, often multi-ply truss that carries the load of other trusses or of a point load.
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