When designing your roof you need to be aware of the spanning capabilities of each thickness of sheet, in other words the maximum width of each sheet you should use. Lower thicknesses of polycarbonate sheet are not as strong or rigid when compared to thicker sheets, so the allowed unsupported spans are less.

To make things easier we have given the recommended maximum spans of each thickness of polycarbonate sheet below:

The maximum recommended spans by sheet thickness are:

10mm Twinwall polycarbonate                 600mm centres

16mm Triplewall polycarbonate               900mm centres

25mm  Multiwall polycarbonate               1050mm centres

35mm Multiwall polycarbonate               1200mm centres

Other important considerations:

If your roof uses self support roof bars you must also take into account the spanning capabilities of the glazing bars you are using and their recommended centres over a range of lengths. The table shows the recommended spans our self support glazing system for polycarbonate and glass. 

If you have a rafter supported roof you must also take into account the length of the sheets. If they are very long it would be wise use additional purlins or noggins and use fixing buttons for extra security.

You must also consider if the area is exposed or in a coastal location. Narrower spans must be used in those circumstances and you must choose glazing bars that are suitable.

Additionally, if the roof is an open structure like a canopy you should keep your centres down around 600mm for all sheet thicknesses and often 500mm for glass.

If in doubt give us a call on 01536 446395 and we will be able to help and advise you further.