![]() This was provided by diagonal braces that were either 150 x 25 mm solid bracing cut in between rafters, or continuous bracing fixed below the rafters for roof plane bracing, and bracing from the ridge board at the gable ends to an internal wall top plate for the roof space bracing. Hipped roof construction does not require additional bracing but gabled roofs require both roof plane and roof space bracing. Purlins, typically 75 x 50 mm and fixed across the rafters, were spaced at 760-900 mm centres depending on the roof cladding. Rafters were birdsmouthed over the top plate and extended beyond the wall framing to create the eaves. Ridge boards were 25 mm (1") wide with a depth dependent on the rafter size. Rafters were typically (ex.) 100, 125 or 150 x 50 mm depending on span, and spaced at 900 or 450 mm centres. On-site framing of gabled roofs generally used couple-close construction - that is, where each pair of rafters are tied at their bases by ceiling joists to prevent spreading. ![]() ![]() The introduction of NZS 3604 in 1978 gave specific requirements for rafter, purlin and ceiling joist sizes and spacing. Skillion or exposed rafter roofs were framed up on-site.Īs with wall framing, roof framing timber was often green or wet, which could lead to shrinkage problems and sagging where long spans were not supported until the timber dried. ![]() Off-site roof framing consisted of prefabricated timber trusses, while on-site roof framing consisted of a framework of rafters, ridgeboard or a ridge beam, underpurlins and underpurlin struts, and collar ties and cleats. The roof could be constructed on- or off-site. ![]()
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