Polycarbonate Carport Roofing

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1.   Polycarbonate sheet, trimmed and taped.

2.   Glazing bars to join the sheets.

3.   F Section to finish and secure the edges.

4.   Fixing buttons to secure larger sheets between the bars.

5.   Sheet closure for the bottom edge.

6.   Foilband flashing (polycarbonate compatible) to seal the top against a wall.

7.   Guttering.


10mm structured polycarbonate is the material for an open sided carpot or pergola, there is little point in choosing the extra cost of 16mm or thicker.  For a conservatory, choose the thickest you can afford giving extra insulation.  Use the widest sheet you can comfortably handle, this will reduce the number of glazing bars required keeping costs down.  It is very easy to underestimate the size and difficulty of handling sheets particularly in windy conditions.


We recommend rafters at 600mm or 700mm centres depending on the width of sheet used (maximum width 1830mm or 2100mm).  This will support the sheet on both edges and twice in between.  F Section is used to start and finish the carport and glazing bars used to connect the sheets.  Fixing buttons are used on the support rafters between the glazing bars.  Decide which sheet you would like then check available widths.  Ideally we would suggest your Timber to be at 610mm centres (10mm Twinwall or Borg) or 700mm centres (all other polycarbonate).


PVCu corrugated sheets are normally fixed to purlins. Screw down bars do not work on purlins.  Though not recommended by manufacturers, snap down bars can be used to cross purlins, Timber rafters would be better, then any bar can be used and with more fixings. The important point here is the number of fixings points holding your roof down.  E.g a 3m projection with purlins may only have 4 fixings points per bar, imagine a sudden gust of wind underneath that. Better too many fixings than not enough.


The manufacturers minimum recommended pitch is 5degrees, to cover adequate drainage, this is a fall of 265mm over 3000mm. This is a minimum, we would recommend a fall of 500mm.


Both ends of the polycarbonate sheet should be taped to stop dust and insects entering the flutes.  Breather tape should be used at the bottom allowing air as it expands and contracts to exit and enter the flutes.  Nick Gray supplies sheets trimmed and taped free of charge.

Please visit our ebay shop for photographs and sheet comparisons.




A roof supporting beam that runs from top too bottom, the slope.

A roof supporting beam that runs horizontal, sometimes supporting rafters or  
running between them.

Glazing bar   
Joins two sheets of polycarbonate together.

Self supporting   
Acts as a rafter as well, needing no support.

Timber supported 
Needs to sit on a timber support. Snap down has an aluminium base which is screwed onto the timber and has  a plastic snap on capping, though not recommended this bar can be used crossing purlins particularly when replacing corrugated sheet. Screw down bar has a rubber base and can only be used on a rafter. The capping is aluminium and screwed into the rafter. This is the stronger and more professional method suitable for all thickness’s of polycarbonate.

Edge bar            
A bar used on the sides to finish off with polycarbonate on one side only.
Sometimes an adapted main bar and not always available from every manufacturer.

Edge trim            
Converts a main snap down bar into an edge bar.

F section            
Used instead of an edge bar. Useful with its leg that can be used down or up if against a wall. Plastic  or aluminium depending on thickness.

Breather tape   
Put on the bottom of the sheet allowing  air in and out of the flutes as it expands and contracts while  keeping dust and insects out.

Plastic U section with a drip that protects the breather tape and stops water running up the underside of the sheet.

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