Roofing Installation Tips

Polycarbonate Roofing – Installation Advice & Best Practices

When installing polycarbonate roofing, doing it right matters. Proper installation not only ensures weather-tight performance and structural strength, but also maximises the life and looks of your panels. Below are our top tips to guide you through planning, preparing, and installing with confidence.

Framework & Planning

Ensure a solid framework: Glazing bars alone cannot support the weight of polycarbonate sheets. Always install on a sturdy timber rafter structure.
Rafter size: With a 50 mm glazing bar width, we recommend rafters 50–60 mm wide to ensure proper support.
Roof pitch: Maintain a minimum pitch of 10° (around 175 mm fall per metre). Lower pitches risk water pooling and poor runoff.
Sheet overhang: Extend sheets no further than 150 mm; most installations use 50–100 mm for stability and aesthetics.
Allow for thermal expansion: Leave 3 mm clearance on each side of your sheets to accommodate natural expansion and contraction.
Sheet width calculation: Include 7.5mm per side for glazing bars when measuring your panels.

Preparing Your Polycarbonate Sheets

Protective film: Lift 50 mm of the protective film on either side of each sheet during installation. Only remove the film completely after sheets are fitted.
UV protection: Multiwall Polycarbonate is UV-protected on one side—ensure this side faces upwards towards sunlight.
Aluminium Tape: Apply to the top exposed ends to reflect heat and block moisture.
Anti-Dust Tape: Apply to the bottom exposed ends to keep debris and insects out of the sheet cells.

Installing Glazing Bars & Panels

Align glazing bars: Centre each bar on your rafter and ensure it is fully supported along its length.
Drill fixing holes: Drill through the centre of the aluminium base between the toothed legs.
Fixing holes should: Sit for No. 5 wood screws, be 75 mm from each end, be spaced no more than 400 mm apart
Attach bars: Screw the aluminium base firmly using suitable wood screws.
Position sheets: Place polycarbonate sheets onto the glazing bar bases carefully.

Securing the Sheets

PVC top caps: Push the top cap legs into the aluminium base slots, working top to bottom for a firm seal. Do not use a rubber mallet.
End sides: If sheets have exposed left and right sides, finish with an Aluminium F-Section, slotting the sheet between the prongs. Screw the F-Section into the rafter or wall as appropriate.
Glazing bar end closure: Use a PVC F-Section with snapdown cap to seal exposed ends of glazing bars

Sheet End Closures & Silicone

Fitting closures: Trim Sheet End Closures to size if necessary. Some installers fit closures to the sheets before positioning.
Seal edges: Run a bead of silicone along the top edge for a secure seal. Slide and tap the closure into place.
Leave ventilation: Avoid excessive silicone—panels must breathe to reduce condensation.

Fixing Buttons & Plastic End Caps

Drill holes: Make holes 2 mm wider than the fixing button shank to allow thermal movement.
Button spacing: Fit at 300 mm intervals and no closer than 50 mm from cut edges.
Do not overtighten: Push the cover cap into place and optionally apply a small amount of silicone around the screw top.
Plastic end caps: Fit to the front (and back if required) of glazing bars for a neat finish.

Additional Notes

Guttering: You may fashion your own guttering system if required. Note: We do not supply guttering items—they must be sourced separately.
Maintenance: Inspect sealants, closures, and fixings regularly, especially after storms or seasonal changes. Clean sheets with mild soap and soft cloth; avoid abrasive cleaners.

Following these basic steps ensures your polycarbonate roof is secure, weatherproof, and long-lasting while reducing the risk of leaks, noise, or condensation.