Polycarbonate roofing sheets are a popular choice for everything from pergolas and lean-to roofs to carports, canopies and garden buildings. They're lightweight, durable and allow natural light into the space below, making them a practical alternative to traditional roofing materials for many projects.
However, once you've decided to use polycarbonate, there's another important decision to make: what thickness polycarbonate sheet do you need?
Multiwall polycarbonate roofing sheets are available in several thicknesses, and choosing the right one can affect the strength, insulation, appearance and overall performance of your finished roof.
In this guide, we'll look at the differences between 10mm, 16mm and 25mm polycarbonate sheets, where each thickness is commonly used and what you should consider before ordering.
What Thicknesses Do Polycarbonate Roofing Sheets Come In?
Polycarbonate roofing sheets are available in a wide range of thicknesses, but 10mm, 16mm and 25mm are three of the most common options used for domestic roofing projects.
The thickness isn't the only difference between them. As sheets become thicker, their internal multiwall structure can also change, providing different levels of rigidity and thermal performance.
As a general overview:
| Thickness | Typical Uses | Key Advantage |
|---|---|---|
| 10mm | Pergolas, canopies, smaller garden structures | Lightweight and economical |
| 16mm | Lean-tos, carports, verandas and general roofing | Excellent all-round option |
| 25mm | Garden rooms, conservatories and more substantial roofs | Improved rigidity and insulation |
There isn't one thickness that's automatically best for every roof. The correct choice depends on the structure you're covering, the supporting framework and the level of performance you need.
Is 10mm Polycarbonate Suitable for Roofing?
Yes. 10mm polycarbonate sheets can be used for a variety of roofing applications and are particularly useful where you want a lightweight and economical roofing material.
10mm sheets are commonly used for:
- Pergolas
- Covered seating areas
- Canopies
- Smaller lean-to roofs
- Garden structures
- DIY roofing projects
Their relatively low weight makes the sheets straightforward to handle and install, while the twinwall construction provides greater rigidity than a single solid sheet of similar weight.
For smaller outdoor structures where high levels of insulation aren't a priority, 10mm polycarbonate can provide a practical and cost-effective solution.
However, the supporting structure and glazing system must always be designed for the sheet being installed. You shouldn't simply choose a thinner sheet because it's cheaper without considering the requirements of the complete roof.
When Should You Use 16mm Polycarbonate Sheets?
For many general roofing projects, 16mm polycarbonate sheets provide an excellent middle ground between weight, rigidity, insulation and price.
They are commonly used for:
- Carports
- Lean-to roofs
- Verandas
- Pergolas
- Covered walkways
- Patio covers
- Larger garden structures
The increased thickness provides greater rigidity and improved thermal performance compared with thinner sheets, while remaining lightweight enough to handle relatively easily during installation.
This makes 16mm polycarbonate a particularly versatile choice.
If you're building a typical domestic polycarbonate roof and aren't sure whether you need the lightest or thickest option available, 16mm is often a sensible place to start your comparison.
That doesn't mean it's automatically suitable for every project. Rafter spacing, roof pitch, exposure and the glazing system being used all need to be taken into consideration.
What Are 25mm Polycarbonate Sheets Used For?
25mm multiwall polycarbonate sheets are generally chosen where improved rigidity and thermal performance are more important.
Typical applications include:
- Garden rooms
- Conservatory-style roofs
- Larger lean-to roofs
- Enclosed outdoor areas
- Carports
- Verandas
- More substantial polycarbonate roofing projects
The thicker multiwall construction creates additional air spaces within the sheet. These help improve thermal performance while creating a more substantial roofing panel.
For an open-sided pergola or simple canopy, that additional insulation may offer relatively little benefit. For a more enclosed space, however, it can become much more important.
This is why the intended use of the area beneath the roof should be considered alongside the size of the structure itself.
10mm vs 16mm vs 25mm Polycarbonate Sheets
If you're comparing the three most common thicknesses, it helps to look at their characteristics side by side.
| Feature | 10mm | 16mm | 25mm |
|---|---|---|---|
| Weight | Lightest | Lightweight | Heavier |
| Rigidity | Good | Increased | Highest of the three |
| Thermal performance | Basic | Improved | Better |
| Handling | Very easy | Easy | Manageable |
| Typical project | Smaller/light-duty roofs | General-purpose roofing | More substantial/enclosed roofs |
| Relative cost | Lower | Mid-range | Higher |
The important thing is not to assume that thicker automatically means better.
A 25mm sheet may provide improved insulation and rigidity, but those benefits may be unnecessary for a simple open pergola. Equally, choosing 10mm purely to reduce the cost of a more demanding roofing project may not provide the performance the structure requires.
The aim should always be to select the most appropriate polycarbonate sheet for the project, rather than simply the thickest or cheapest option.
Does Thicker Polycarbonate Provide Better Insulation?
Generally, yes.
Multiwall polycarbonate sheets contain internal chambers that trap air within the sheet. These air pockets help reduce heat transfer through the roof.
As the thickness and multiwall construction increase, thermal performance will generally improve.
This means a thicker sheet can be particularly useful when roofing a more enclosed space such as a garden room or conservatory-style structure.
For open structures such as pergolas and carports, insulation is usually much less important because the space underneath isn't being heated.
It's therefore worth asking a simple question:
Do you need the roof primarily to provide shelter and daylight, or will the space underneath also need improved thermal performance?
The answer can help determine whether paying for a thicker sheet is worthwhile.
Does Thicker Polycarbonate Mean a Stronger Roof?
A thicker multiwall sheet will generally provide increased rigidity, but sheet thickness alone doesn't determine the strength of a polycarbonate roof.
The complete roofing system also depends on factors including:
- Rafter spacing
- Supporting framework
- Glazing bars
- Roof pitch
- Sheet dimensions
- Fixings
- Local weather exposure
- Correct installation
This is particularly important on larger roofs or structures in more exposed locations.
Always follow the relevant manufacturer's span tables and installation guidance rather than selecting sheet thickness based on appearance alone.
What Is Multiwall Polycarbonate?
Rather than being one solid piece of plastic, multiwall polycarbonate contains multiple layers connected by internal ribs.
When viewed from the end, you can see channels running through the sheet.
This construction provides several advantages. It keeps the sheet lightweight while increasing rigidity and creating insulating air spaces within the panel.
Different products may be described as:
- Twinwall
- Triplewall
- Multiwall
Twinwall sheets have two outer layers connected by internal ribs, while other multiwall designs incorporate additional internal layers and more complex structures.
This allows manufacturers to increase performance without creating an excessively heavy roofing sheet.
What Colour Polycarbonate Sheet Should I Choose?
Once you've chosen the appropriate thickness, you'll also need to decide which colour or finish is right for your project.
Polycarbonate roofing sheets are commonly available in clear, bronze and opal, with some ranges also offering additional tinted options.
Clear Polycarbonate
Clear polycarbonate allows the greatest amount of natural daylight through the roof.
It's a popular option for:
- Lean-to roofs
- Pergolas
- Canopies
- Carports
- Covered walkways
- Areas where maintaining natural light is important
If your main priority is creating a bright space underneath the roof, clear sheets are usually the obvious starting point.
Bronze Polycarbonate
Bronze polycarbonate has a tinted appearance that helps soften incoming sunlight and reduce glare.
It's particularly popular for:
- Pergolas
- Verandas
- Patio covers
- Outdoor seating areas
- South-facing structures
The bronze tint also creates a warmer appearance that can work particularly well alongside timber frames.
Opal Polycarbonate
Opal polycarbonate provides a more diffused light rather than allowing direct sunlight through the roof.
This can help create a softer and more evenly lit space underneath.
Opal sheets are worth considering where you want:
- Reduced glare
- More privacy
- Diffused daylight
- A softer appearance beneath the roof
The best option ultimately depends on how much light you want underneath the structure and the appearance you're trying to achieve.
What Thickness Polycarbonate Should I Use for a Pergola?
For many pergolas and covered seating areas, 10mm or 16mm polycarbonate sheets may be suitable.
10mm sheets provide a lightweight and economical option, particularly for smaller structures, while 16mm sheets offer additional rigidity.
The correct choice will depend on the size and design of your pergola, the spacing between supports and the glazing system being used.
For larger pergolas or more exposed locations, it's particularly important to check the manufacturer's recommended spans before deciding which sheet to use.
What Thickness Polycarbonate Should I Use for a Carport?
16mm polycarbonate is a popular option for carports because it provides a useful balance between rigidity, weight and cost.
However, carports can vary considerably in size and design.
A small carport with closely spaced supports has very different requirements from a large structure spanning several metres. The correct sheet thickness should therefore be selected alongside the supporting framework rather than independently from it.
For larger or more substantial structures, 25mm sheets may also be considered where compatible with the roofing system.
What Thickness Polycarbonate Should I Use for a Lean-To Roof?
Both 16mm and 25mm polycarbonate sheets are commonly considered for lean-to roofing.
For an open-sided lean-to or patio cover, 16mm may provide everything you need.
For a more enclosed structure where improved insulation is desirable, 25mm multiwall sheets may be more appropriate.
As with any polycarbonate roof, the sheet must be compatible with the glazing bars and supporting structure being used.
What Accessories Do I Need for Polycarbonate Roofing Sheets?
The sheets themselves are only one part of a complete polycarbonate roofing system.
Depending on the design of your roof, you may also require:
- Glazing bars
- Side flashing
- F-sections
- Sheet closures
- Breather or anti-dust tape
- Aluminium sealing tape
- Fixing buttons
- Wall flashing
- Suitable fixings
Using compatible accessories is important because polycarbonate expands and contracts as temperatures change.
A correctly designed glazing system allows for this movement while helping keep the roof secure and weather-resistant.
Before ordering, it's therefore worth planning the complete roofing system rather than calculating the number of sheets alone.
Common Mistakes When Choosing Polycarbonate Sheets
Choosing polycarbonate roofing isn't particularly complicated, but a few common mistakes can cause unnecessary problems.
These include:
- Choosing sheet thickness based purely on price
- Assuming the thickest sheet is always the best option
- Ignoring recommended support spacing
- Buying sheets before planning the glazing system
- Mixing incompatible sheets, glazing bars and accessories
- Forgetting to allow for thermal expansion
- Choosing a tint without considering how much daylight you want below
- Failing to check the manufacturer's installation guidance
Planning the complete roof before ordering can help avoid many of these issues.
Which Polycarbonate Thickness Is Right for Your Project?
For smaller, relatively simple structures where insulation isn't a major concern, 10mm polycarbonate can provide an economical and lightweight roofing solution.
For general-purpose domestic roofing, 16mm polycarbonate offers a useful balance of rigidity, thermal performance and affordability, making it suitable for a wide variety of projects.
Where improved insulation or a more substantial multiwall sheet is required, 25mm polycarbonate may be the better choice.
However, these are general guidelines rather than fixed rules.
Your supporting structure, rafter spacing, roof dimensions and glazing system should always be considered before deciding which sheet thickness to purchase.
Frequently Asked Questions
Is 10mm polycarbonate thick enough for a roof?
10mm polycarbonate can be suitable for smaller canopies, pergolas and other lightweight roofing applications when installed on an appropriately designed supporting structure. Always check the manufacturer's recommended support spacing and installation requirements.
Is 16mm polycarbonate better than 10mm?
Neither is automatically better. 16mm polycarbonate generally provides increased rigidity and improved thermal performance, while 10mm sheets are lighter and can be more economical. The best option depends on the type of roof you're building.
Is 25mm polycarbonate worth it?
For more enclosed spaces or projects where improved thermal performance and rigidity are important, 25mm polycarbonate can be worth the additional cost. For a simple open-sided canopy or pergola, the extra insulation may be unnecessary.
What is the best thickness of polycarbonate for a pergola?
10mm and 16mm polycarbonate sheets are commonly considered for pergolas. The appropriate thickness depends on the size of the roof, supporting framework, rafter spacing and manufacturer's recommendations.
What thickness polycarbonate should I use for a carport?
16mm polycarbonate is a popular general-purpose option for carports, although the correct thickness depends on the design, dimensions, support spacing and exposure of the structure.
Does thicker polycarbonate let in less light?
Light transmission isn't determined by thickness alone. The internal structure and colour of the sheet also affect how much light passes through it. Clear, bronze and opal sheets of the same thickness can therefore produce noticeably different lighting conditions below the roof.
Can I cut polycarbonate roofing sheets?
Polycarbonate sheets can generally be cut to size using suitable tools and methods, but the manufacturer's cutting and installation instructions should always be followed. Once cut, exposed multiwall sheet ends also need to be correctly sealed or vented as required by the roofing system.
Can you walk on polycarbonate roofing sheets?
You should not walk directly on unsupported polycarbonate roofing sheets. If access is required during installation or maintenance, appropriate crawl boards or other safe access methods should be used in accordance with the manufacturer's instructions and relevant working-at-height requirements.
Explore Trusted Polycarbonate Roofing Sheets
At Trusted Building Supplies, we offer a range of Trusted Polycarbonate Roofing Sheets designed to provide a cost-effective solution for domestic and trade roofing projects.
Our range includes:
- 10mm polycarbonate roofing sheets
- 16mm polycarbonate roofing sheets
- 25mm polycarbonate roofing sheets
- Clear, bronze and opal options
- Glazing bars and joining profiles
- Sheet closures and end profiles
- Sealing and breather tapes
- Flashing and installation accessories
Whether you're covering a pergola, building a carport or creating a new lean-to roof, choosing the correct sheet thickness and compatible accessories will help you create a durable, practical and professional-looking finish.
Related Guides
- Corotherm vs Trusted Polycarbonate Roofing Sheets: Which Should You Choose? (Coming Soon)
- Clear vs Bronze vs Opal Polycarbonate Sheets (Coming Soon)
- How to Install Polycarbonate Roofing Sheets (Coming Soon)
- Polycarbonate vs PVC Roofing Sheets: What's the Difference? (Coming Soon)
Why Choose Trusted Building Supplies?
Trusted Building Supplies is a family-owned independent builders' merchant supplying high-quality building materials to customers across the UK. We work with leading manufacturers and trusted suppliers to offer competitive prices, fast nationwide delivery and expert advice to help you choose the right products with confidence.
Whether you're a homeowner taking on a garden roofing project or a trade professional completing a larger installation, we're here to support you every step of the way.
Information Notice
This guide has been written by Trusted Building Supplies to provide general information and practical guidance for homeowners, DIYers and trade professionals. Every roofing project is different, so product suitability, structural requirements and installation methods should always be considered before work begins.
Always follow the latest manufacturer's installation guidance, recommended span tables and relevant building requirements. Seek advice from a suitably qualified professional if you're unsure about the structural design, installation or suitability of any roofing product for your project.
Last Reviewed: August 2026