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ANTI SAG SUPPORT FOR FLAT ROOFS (Slope <4°)
Flat Roof
On flatter roofs particular care must be paid to the management of deflection as water ponding can result as a consequence. A typical flat roof construction is depicted in the image above. This is applicable where the cladding used adequately restrains the top flange.
 
Application of cold rolled for slopes less than 4° 
• Purlins are installed as facing pairs. The section size is selected as normal from the load tables.
• Tube Struts are used as the bracing component and installed as shown.
• The struts specified by the table above are for managing distortion due to gravity loads. If uplift must be managed the number of struts should be obtained from the load tables.
 
Number of rows of struts per bay based on span
Purlin section Bay centres (m)
  Up to 6.1 Up to 7.5 Up to 9
All depths 1 2 3