A half truss is a truss that covers only half of a full, symmetrical truss: it runs from the ridge or an existing wall down to one side and bears there. It is used where no full, symmetrical roof is needed.
Characteristics
Where a normal truss forms two roof planes that meet at the ridge, a half truss consists of only one sloping half. On the high side it is supported by the existing structure or by a portal or column; on the low side it rests on the wall plate. This creates a single sloping roof plane that carries the loads to two supports.
Half trusses are made in both timber and steel. Their sizing and pitch follow from the span, the roof covering and the required height on each side.
Applications
A half truss is used for a mono-pitch (lean-to) roof, for an extension built against an existing, taller wall, or at the side of a roof. It is a logical choice when one side connects to existing work and the other lands freely on a wall, such as a conservatory, garage or shed built against the house.
Related terms
- Truss
- Mono-pitch roof
- Purlin
- Wall plate
- Extension
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