Multiwall Polycarbonate Glazing Sheet

4mm Twinwall Corotherm

4mm Twinwall Corotherm is a light weight, impact resistant polycarbonate sheet, suitable for side cladding only, not suitable for roofing.  It is guaranteed for 10 years.


  • Available in clear for maximum light transmission
  • Light weight glazing sheet
  • UV resistant for durability
  • Durable and hardwearing
  • Minimum condensation risk
  • Largely self-cleaning
  • 10 year warranty

ideal for

  • Cloches
  • Plant Houses
  • DIY Glazing Projects


Refer to the Corotherm installation guide and installation video for complete installation instructions.

Energy Efficiency - Relative U-Values*

Sheet Thickness (mm) Corotherm Single Glass Double Glass  Argon Filled Cavity
4mm (Twinwall)
6mm (Twinwall)




10mm (Twinwall)




16mm (Triplewall) 2.4 5.4 2.65  1.6
25mm (7Xwall) 1.6   -  2.65  1.6

*A Lower U-value indicates increased energy efficiency and thermal insulation 


  • Corotherm 4mm Twinwall is not suitable for roofing, side cladding only 
  • Make sure the clearly marked UV protected side of the sheet is facing outwards
  • Use only low modulus neutral cure sealant and cross-linked butyl flashing tape
  • Sheets cannot be joined top to bottom

Corotherm can be easily cut and will not crack or shatter.  When cutting parallel to the flutes a sharp knife can be used but when cutting across the flutes a fine toothed saw is required.  For cutting curves use a fine toothed jig saw.

Thermal Expansion
When installing Corotherm sheet it is important to allow a sufficient expansion gap at the top end of the sheet.  When drilling fixing holes an expansion allowance of 3mm around all fixings is required.  Do not fix or clamp sheets too tightly- leave room for thermal movement.

Corotherm can be easily and quickly washed with luke warm soapy water and a soft cloth or sponge.  Do not use brushes or sharp objects and avoid any abrasives or cleaners of high alkaline nature.

10 Year Warranty
This product is covered by a 10 year warranty. A replacement is provided free of charge if the product has failed due to a manufacturing defect, in normal climatic conditions within a 10 year period from the date of purchase.

Corotherm MUST be fixed and maintained in accordance with the manufacturer's instructions for the warranty to remain valid: re-erections or consequential damage costs are not included.



Open/close panel Customer service

Get in touch

Contact our customer service team