Selecting the appropriate polycarbonate sheet thickness is an important part of planning a roofing or glazing project. Different thicknesses can influence rigidity, light levels, and sheet suitability for particular applications.

This guide explains what sheet thickness means in multiwall polycarbonate and outlines which options are commonly used for UK projects such as pergolas, canopies, garden rooms, and walkways.

Why Polycarbonate Sheet Thickness Matters

Multiwall polycarbonate sheets are produced in several thicknesses, typically between 4mm and 25mm. Thinner sheets are often used where maximum light transmission and low weight are preferred, while thicker sheets may offer increased rigidity and deeper internal chambers.

Choosing a suitable thickness helps ensure the sheet is appropriate for the project’s design requirements.

Understanding Multiwall Polycarbonate Structure

Multiwall polycarbonate sheets contain internal chambers (flutes). As thickness increases:

• Internal chamber depth typically increases

• Sheet rigidity changes

• Light transmission and shading characteristics vary

This internal structure makes multiwall polycarbonate adaptable for a range of installations.

Common Polycarbonate Thicknesses and Their Uses

4mm Multiwall Polycarbonate Sheets

4mm polycarbonate is generally used for lightweight projects and glazing where maximum light transmission is required.

Typically used for:

• Greenhouses

• Cold frames

• Small glazing projects

• Vertical glazing

6mm Multiwall Polycarbonate Sheets

6mm sheets provide a slightly more substantial option and are commonly used in lightweight roofing and small canopy designs.

Typical uses:

• Small canopies

• Cold frame roofs

• Lightweight lean-to roofing

10mm Multiwall Polycarbonate Sheets

10mm sheets are widely used for outdoor roof structures.

Often selected for:

• Pergolas

• Carports

• Covered walkways

• General outdoor roofing

16mm Multiwall Polycarbonate Sheets

16mm sheets offer deeper multiwall chambers and are commonly used where additional rigidity and shading options are preferred.

Common uses:

• Garden rooms

• Larger pergolas

• Conservatory-style roofs

25mm Multiwall Polycarbonate Sheets

25mm sheets provide the deepest chamber structure in the range and are typically selected for enclosed structures.

Typically used for:

• Garden rooms

• Enclosed patio areas

• Conservatory-style structures

• Larger spans, depending on design

Light and Solar Control Options

Alongside thickness, finish influences light and shading.

• Clear – high levels of natural daylight

• Opal – diffused light and reduced brightness

• Bronze / Bronze Opal – tinted options for lower light levels

• Heat-reflective finishes – help reflect a portion of solar energy

Browse the full finish range here:

Installation Considerations

Correct installation supports performance and longevity. Key considerations include:

• Allowing for thermal expansion

• Installing with the UV-protected face outward

• Using glazing bars appropriate for sheet thickness

• Sealing open flutes with breather tape (bottom) and aluminium tape (top)

• Adding suitable end closures and flashings

Compatible accessories can be found here:
👉 Accessories for Multiwall Polycarbonate

Accessories for a Complete System

Helpful components for multiwall polycarbonate installations include:

• Glazing bars:
  

• End closures:
  

• Breather tape:
  

• Side flashings:
  

These accessories are designed to support correct fitting and edge protection when used with multiwall polycarbonate sheets.

Choosing a Suitable Thickness

When selecting sheet thickness, consider:

• Size of the structure

• Desired light levels

• Whether the area is enclosed or open

• Project budget and design

Checking the requirements of your specific structure or consulting manufacturer guidelines can help ensure a suitable choice.

Browse Multiwall Polycarbonate Sheets

polycarbonatex.co.uk supplies a range of multiwall polycarbonate sheet thicknesses and compatible accessories for complete roofing systems.