When installing polycarbonate glazing sheets, it is essential to allow for thermal expansion and contraction. Like most building materials, polycarbonate expands in warm weather and contracts as temperatures fall. Failing to allow for this movement can lead to stress on the sheet, noise, distortion, or damage to the glazing system.
How Much Do Polycarbonate Sheets Expand?
As a general rule, polycarbonate roofing sheets can expand or contract by approximately 3mm per metre of sheet length in both directions as temperatures change.
This movement must be accommodated during installation to ensure long-term performance.
How Omega Glazing Bars Allow for Movement
All Omega glazing bar systems are designed to allow for the natural expansion and contraction of polycarbonate roofing sheets. The glazing bar caps can move with the sheet, helping to accommodate thermal movement while maintaining a secure and weatherproof installation.
This is one of the key advantages of using a purpose-designed polycarbonate glazing system.
Securing the Polycarbonate Sheet Correctly
To prevent the sheet from creeping down the roof as it expands and contracts, each sheet should be mechanically fixed at one end only.
The recommended fixing point is normally:
- At the wall plate on lean-to roofs
- At the ridge on pitched roofs
Positioning the fixing at these locations allows the screws to be concealed beneath the flashing for a neat, professional finish.
Important Fixing Tip
When fixing polycarbonate glazing sheets, always oversize the fixing hole by 3mm to allow for thermal movement around the fixing point.
This simple step helps prevent stress cracking and allows the sheet to expand and contract freely.
Best Practice for Polycarbonate Roof Installations
To ensure the best performance from your polycarbonate roofing sheets:
- Allow 3mm expansion per metre of sheet length
- Use glazing bars designed for thermal movement
- Fix each sheet at one end only
- Oversize fixing holes by 3mm
- Ensure adequate expansion gaps around all edges
- Follow the glazing bar manufacturer’s installation recommendations
By allowing for expansion and contraction during installation, your polycarbonate roof, conservatory roof, canopy, veranda, or lean-to roof will remain secure, weatherproof, and looking its best for many years to come.
