Polycarbonate roofing sheets are available in several internal structures, with twinwall and triplewall being two of the most commonly used formats. Each has its own characteristics based on the number of internal chambers and the sheet thickness, which can influence rigidity, weight, light levels, and suitability for certain installations.

This guide explains the general differences between twinwall and triplewall multiwall polycarbonate to help you choose an option that works for your project.

Browse all polycarbonate sheet options here:
👉 https://polycarbonatex.co.uk/collections/multiwall-polycarbonate-sheets

What Is Twinwall Polycarbonate?

Twinwall polycarbonate contains two outer layers with a single row of internal chambers (flutes). It is commonly used for lightweight outdoor and garden structures.

Typical Characteristics of Twinwall

• Lightweight and easy to handle

• Allows high levels of natural light

• Often selected for smaller roofs and DIY builds

• Available in several thicknesses

Common Twinwall Thicknesses

• 4mm

• 6mm

• 10mm

Example sheet (10mm):
https://polycarbonatex.co.uk/collections/multiwall-polycarbonate-sheets/products/10mm-corotherm-multiwall-polycarbonate-roofing-sheet-clear

Typical Uses for Twinwall

Twinwall sheets are often chosen for:

• Greenhouses and cold frames

• Pergola covers

• Lean-to roofs

• Small canopies and sheds

Twinwall is generally suited to projects where low weight and brightness are priorities.

What Is Triplewall Polycarbonate?

Triplewall polycarbonate has three layers and two rows of internal chambers. This gives it a deeper structure than twinwall and can influence rigidity and shading depending on thickness and finish.

Typical Characteristics of Triplewall

• Deeper chamber structure

• More substantial feel compared to thinner twinwall sheets

• Can provide a more diffused light depending on finish

• Commonly used for larger installations

Common Triplewall Thicknesses

• 16mm

• 25mm

Examples:
16mm Clear – https://polycarbonatex.co.uk/collections/multiwall-polycarbonate-sheets/products/16mm-corotherm-multiwall-polycarbonate-roofing-sheet-clear
25mm Clear – https://polycarbonatex.co.uk/collections/multiwall-polycarbonate-sheets/products/25mm-corotherm-multiwall-polycarbonate-roofing-sheet-clear

Typical Uses for Triplewall

Triplewall is often selected for:

• Larger pergolas

• Garden rooms

• Covered walkways

• More enclosed structures

It is generally used where a more substantial sheet thickness is appropriate for the design.

Twinwall vs Triplewall: A General Overview

Choosing Between Twinwall and Triplewall

Twinwall May Be Suitable If:

• You’re working on a smaller or lightweight structure

• High light transmission is preferred

• Budget-friendly materials are required

• The roof span is modest

Triplewall May Be Suitable If:

• The structure is larger or more enclosed

• A deeper multiwall structure is preferred

• The project involves a roof used frequently throughout the year

• You want a sheet with more internal chambers

Both sheet types can work well in domestic projects depending on size, design, and desired brightness.

Installation Considerations

Regardless of sheet type, the following points apply to most multiwall polycarbonate installations:

• Allow space for thermal expansion

• Install with the UV-protected side facing outward

• Use glazing bars appropriate for the sheet thickness

• Tape sheet ends with solid tape (top) and breather tape (bottom)

  • Breather tape: https://polycarbonatex.co.uk/collections/multiwall-accessories/products/corotherm-multiwall-polycarbonate-sheet-breather-tape-10m

• Use fixings designed for multiwall polycarbonate

  • Fixing buttons: https://polycarbonatex.co.uk/collections/multiwall-accessories/products/corotherm-multiwall-polycarbonate-sheet-super-fixings-buttons-pack-of-10

Compatible accessories help support correct installation.

Browse Twinwall & Triplewall Polycarbonate Sheets

polycarbonatex.co.uk supplies a full range of multiwall polycarbonate sheets in various thicknesses and finishes, along with glazing bars, tapes, closures, and other accessories needed for installation.

👉 View the full range here:
https://polycarbonatex.co.uk/collections/multiwall-polycarbonate-sheets
👉 View accessories here:
https://polycarbonatex.co.uk/collections/multiwall-accessories