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Common features of roofs, valleys and hip offer design and aesthetical benefits, but provide a potential weak spot within a truss rafter construction. Always construct in accordance with the approved design.
Diminishing trusses for a valley formation begin with a double full truss at the bottom of the sequence.
100mm x 25mm is fixed to the adjoining roof to support the node points of the diminishing trusses.
Diminishing trusses are fixed twice into the adjoining rafters using 75mm galvanised nails, then;
Splayed battens are placed against the diminishing truss on every adjoining rafter and fixed.
Exterior grade timber board placed between the trusses to support the GRP valley system.
Size and position of the timber would be determined by the GRP valley manufacturer.
Box gutters to be formed using external grade ply.
Minimum step height is 50mm.
Provide a minimum of 150mm deep kerb.
Hipped roofs formed using truss rafters with diminishing mono pitched trusses should be supported by a girder truss.
Birds mouth cuts should not exceed 1/3 of the depth of the hip tree.
Angle ties should be used at the corner to prevent the wall plates from spreading.
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