Choosing Width of Polycarbonate Roof Sheets

When it comes to roofing, the precision in selecting the right materials can make or break the functionality and aesthetic of your project. Twinwall Polycarbonate Sheets, known for their durability and versatility, are a popular choice for roof glazing.

However, picking the right width for these sheets is not a one-size-fits-all decision. Factors such as sheet thickness, the location and specifics of your project, and the pitch of your roof all play crucial roles.

This guide explores these different variables to help you make an informed decision.

Section 1: Critical Factors for Selecting Sheet Width

Selecting the ideal width for Twinwall Polycarbonate Sheets involves several key considerations:

  • Sheet Thickness: Determines the spanning capability and overall structural integrity.
  • Type of Rafter Support: Influences the feasibility and strength of the roofing.
  • Thermal Expansion and Contraction: Ensures longevity and durability.
  • Ease of Installation: Affects the practicality and safety of the installation process.
  • Safety: Paramount in ensuring a risk-free installation and maintenance.

Section 2: Importance of Sheet Thickness

The thickness of your polycarbonate sheets is a vital factor in determining their suitability for your project. As a rule of thumb, the thicker the twinwall sheets the wider you can span. However, there should be a general limit of 1050mm in most applications.

  • Thinner Sheets (6mm, 10mm):
    • More economical but require more support (rafter support at 450-600mm).
    • Suitable for lower-budget projects but may compromise on strength.

  • Thicker Sheets (16mm, 25mm):
    • Can span wider areas (700mm – 1050mm), reducing the need for numerous rafters.
    • Ideal for projects where longevity and strength are priorities.

  • Cost vs. Durability: While thicker sheets might be more expensive upfront, they could save costs in the long run due to fewer structural supports needed and increased durability.

Section 3: Understanding Rafter Support Types

The structure of the rafters is an essential aspect to consider when choosing your polycarbonate sheets.

  • Timber Rafters:
    • More affordable and offer a traditional aesthetic.
    • Require more maintenance and are less durable compared to aluminum.

  • Aluminium Rafters:
    • More expensive but provide better strength and require little to no maintenance.
    • Offer consistent quality and are less prone to warping or damage.

  • Combining Materials: Sometimes, a combination of timber and aluminum can offer a balance between cost-effectiveness and durability. 

Section 4: Expansion and Contraction Challenges

Polycarbonate sheets expand and contract with temperature changes, which must be considered when selecting the width.

  • Thermal Dynamics: Allowing space between each sheet for thermal expansion and contraction is crucial to prevent warping.
  • Maximum Width Recommendations: Generally, it’s advised not to exceed 1050mm in width to accommodate these changes.
  • Special Considerations: In areas with less sunlight exposure, wider sheets might be feasible, but consulting with experts is advised. Learn more about Thermal Dynamics in Roofing.

Section 5: Installation Ease and Safety

The width of the polycarbonate sheets directly impacts the ease of installation and safety.

  • Manageable Sizes: Narrower sheets are easier to handle and install, especially in windy conditions.
  • Installation Challenges with Wider Sheets: Wider sheets can be unwieldy and increase the risk of accidents or damage.
  • Safety Precautions: Using the correct tools and safety equipment is critical when installing these sheets. Discover more about Safe Installation Practices.

Section 6: Choosing Width for Solid Polycarbonate Sheets

While this guide primarily focuses on twinwall sheets, it’s worth noting the differences with solid polycarbonate sheets.

  • Solid Sheets: Offer clearer visibility and better impact resistance but require closer rafter spacing (400mm – 600mm).
  • Structural Considerations: Additional supports like noggins or curved rafters can increase the width for solid sheets.
  • Professional Consultation: Always advisable to consult with a structural engineer for precise requirements


Selecting the right width for Twinwall Polycarbonate Sheets is a nuanced decision that impacts the effectiveness, durability, and safety of your roofing project.

By considering factors such as sheet thickness, rafter support, thermal dynamics, installation ease, and safety, you can ensure a successful implementation. Remember, while this guide provides a comprehensive overview, consulting with professionals for specific advice tailored to your project is always recommended.

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If you're planning a roofing project and need further assistance or have questions, don't hesitate to reach out to our team. For more resources and guidance, explore our blog.

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