Trusses are engineered frames that support a roof covering and transfer its load to the walls. They are typically made from timber, or sometimes steel, and are used instead of traditional cut rafters on many modern houses.
In UK housing, the most common type is the trussed rafter: a prefabricated timber frame of rafters, ceiling tie and internal webs joined with punched metal plates, designed and made by a specialist manufacturer. Trusses are quick to erect, but their internal webs leave little usable loft space unless attic trusses are specified. Points to watch include:
- trusses must not be cut or altered on site without the designer’s approval
- bracing and restraint straps are essential and must be installed as designed
- they are usually priced per truss from the manufacturer, with separate allowances for bracing and installation
Related terms: rafters, ridge, attic truss, wall plate.
