Traditional Cut Purlin Roof

A traditional cut timber roof incorporating a collar for lateral restraint purlins for rigidity and struts to distribute some of the load to an internal load bearing wall.

Traditional cut purlin roof.

They span from the wallplate to the ridge board providing a platform for the underlay battens and tiles. For example an 8 x 4 under purlin would support the center of a row of 6 x 2 rafters that in turn would support 3 x 2 roof purlins to which the roof cladding was fixed. The overall construction of a traditional cut roof is to ensure that the load of the roof is evenly transmitted to the walls below. This roof shown on a previous page is a good example of a traditional cut roof with dormers.

It has a timber purlin on each slope built into the gable ends. In traditional timber truss construction purlins rest on the principal rafters of the truss. From the 1970s onwards most low rise domestic pitched roofs have been formed with trussed rafters. A cut roof this is the traditional method of cutting the timber on site and building up the roof using rafters ridge boards joists and purlins etc the exact details being determined by the size of roof size of timbers etc.

A truss roof using factory made trusses which are delivered to site complete and just erected. The roof support system is a ridgepole and either rafters which run perpendicular from the top of the walls to the ridge or purlins which run parallel to the ridge.