Purlins typically 75 x 50 mm and fixed across the rafters were spaced at 760 900 mm centres depending on the roof cladding.
Purlin spacing for metal roofing nz.
Metalcraft roofing s structural division manufactures metalcraft super span shortened to mss purlins and girts for the new zealand construction market and the pre engineered garages and sheds market segment.
It often depends on the wideness thickness and the types of roofing materials the climate it has to withstand and many other factors.
When the radius of curvature is close to the minimum the purlin spacing should be reduced to the end span distance for each gauge and profile.
The purlin spacings should be limited to the lower of the trafficable limitations and design wind load with the capacity of the structure.
April 2012 nz metal roof and wall cladding code of practice table of contents v 2 2 page 3 table of contents 1 1 0 table of contents 2 0p erformance 3 0 construction load 4 0 d esign 5 0f lashings 6 0p enetrations 7 0i nstallation 8 0 roof drainage 9 0 plastic roof lighting 10 0 pressed metal tiles.
Mss purlins and girts are available in a variety of sizes and gauges cut to length and prepunched to suit a variety of applications.
New zealand metal roofing manufacturers inc.
Fastener patterns on nzs 3604 buildings should be consistent throughout the roof excluding top and bottom rows.
Purlins are non pressure treated 1 x 4 x 12 lumber that is installed on to the roof in a specific layout pattern and screw pattern.
The adjustable cleat can be rotated up to 15 degrees from normal to accommodate the change in angle from vertical portal to the roof slope of the rafter.
For the lighter material such as lightweight aluminum the common spacing length is 4 inches of clear gap.
It should be noted that timber purlins for metal roof cladding are minimum 70mm x 45mm h1 2 18 moisture content and that battens used previously for tiles must not be used.
This result should be referenced to the wind load span design graphs.
For a fuller explanation of this refer to the nz metal roof and wall cladding code of practice.
Where the end purlin spacing is less than 800mm an adjustable end brace with a bolted end cleat is available as twisting of the end cleat is not practical.
If a design quotes wind speed in m s ask for a roof plan showing design loads and purlin spacing apply serviceability loads for pierce fastened products ultimate loads for clip fastened profiles.
The purpose of the purlins is to provide a solid foundation for the metal roofing panels and trim to be screwed to.
Roof bracing hipped roof construction does not require additional bracing but gabled roofs require both roof plane and roof space bracing.
Do all roofing projects require purlins.
