For larger spans and thinner walls, this can topple the walls. Rafters have a tendency to flatten under gravity, thrusting outwards on the walls. The space between each truss is known as a bay. Trusses usually occur at regular intervals, linked by longitudinal timbers such as purlins.
This is an example of a 'double roof' with principal rafters and common rafters.Ī timber roof truss is a structural framework of timbers designed to bridge the space above a room and to provide support for a roof. Key: 1: ridge beam, 2: purlins, 3: common rafters. Two king post trusses linked to support a roof.
