How Thick Should My Polycarbonate Sheets Be?

Choosing the right polycarbonate sheet thickness largely depends on what you’re building and the type of polycarbonate you’re using.

A greenhouse, for example, has very different requirements from a conservatory or enclosed roof. Likewise, corrugated polycarbonate sheets can be much thinner than multiwall sheets because their profiled shape provides additional rigidity.

Keep reading for the typical polycarbonate thicknesses used in common roofing projects and how to choose between them.

What Thickness Polycarbonate Do I Need?

As a starting point, the following thicknesses are commonly suited to these types of projects:

Project	Typical polycarbonate thickness
Greenhouse	4mm–10mm multiwall
Pergola	10mm–16mm multiwall or corrugated polycarbonate
Carport	10mm–16mm multiwall or corrugated polycarbonate
Lean-to	10mm–16mm multiwall
Conservatory	25mm–35mm multiwall
Garden room or enclosed roof	16mm–35mm multiwall
Small canopy or porch	Around 4mm–6mm solid polycarbonate

What Else Affects the Thickness You Need?

Before choosing a sheet you'll also need to consider:

• Support spacing: Wider gaps between rafters, battens or purlins generally place more demand on the sheet.

• Roof size and exposure: Larger or more exposed roofs may require a more rigid sheet or closer support centres.

• Sheet construction: Corrugated, multiwall and solid polycarbonate behave differently, so their thicknesses can't be compared directly.

• Existing roof systems: Replacement sheets need to fit the glazing bars, fixings and other components already in place.

• Manufacturer span guidance: Always check the maximum permitted support centres for the exact sheet you are using.

With those factors in mind, you can then narrow down the most suitable thickness for your project.

Corrugated, Multiwall and Solid Polycarbonate - Which One?

Multiwall and corrugated are the most common polycarbonate choices for the roofing applications covered below.

While solid polycarbonate can also be used for roofing, it's generally heavier and more expensive than comparable corrugated or multiwall options, so it's less commonly chosen for everyday domestic roofs.

What Thickness Polycarbonate for a Greenhouse?

For most domestic greenhouses, 4mm to 6mm polycarbonate is a common choice.

These thinner multiwall sheets keep the glazing lightweight while allowing plenty of natural light into the greenhouse. 6mm polycarbonate offers greater rigidity than 4mm and is a popular middle ground for domestic structures.

For larger greenhouses, 10mm multiwall polycarbonate is another option where the frame is designed to accommodate it.

Alongside thickness, light transmission is particularly important for greenhouse glazing, so consider both when comparing sheets.

What Thickness Polycarbonate for Pergolas, Carports and Lean-Tos?

Pergolas, carports and lean-tos are all relatively simple, lightweight roof structures, so their polycarbonate requirements are usually similar.

For most domestic projects, 10mm or 16mm multiwall polycarbonate is a sensible choice, while corrugated polycarbonate is also commonly used where a simpler profiled roof is preferred.

In general, 10mm suits smaller roofs, while 16mm provides greater rigidity for larger structures.

The main distinction is how the space is used. Pergolas and carports are normally open-sided, whereas lean-tos may be more enclosed or used as semi-internal spaces.

Learn more about adding a roof to an existing pergola here.

What Thickness Polycarbonate for a Conservatory Roof or Other Enclosed Roof?

Conservatory roofs commonly use 25mm, 32mm or 35mm multiwall polycarbonate.

If you're replacing existing panels, the most important thing is to match the new sheets to the glazing bars and fittings the roof is designed to accept. A thicker sheet isn't automatically suitable if the existing system can't accommodate it.

Before ordering, check the thickness of your current panels and, where possible, the specification of the existing roof system.

Learn more about choosing polycarbonate for a conservatory roof replacement here.

Does Polycarbonate Thickness Affect Insulation?

Polycarbonate roofing offers very little meaningful insulation, regardless of thickness.

Multiwall sheets reduce heat transfer more effectively than solid or corrugated polycarbonate because of the air trapped within their internal chambers, and thicker multiwall sheets generally perform slightly better.

However, even thick multiwall polycarbonate shouldn't be treated as an insulating roof material. Thickness should therefore be chosen mainly according to the roof and glazing system rather than with the expectation that a thicker panel will make the space significantly warmer.

Does Thicker Polycarbonate Mean Stronger?

Usually, yes - within the same type of polycarbonate, a thicker sheet will generally be more rigid and able to span further without flexing (within the manufacturer's specs).

But thickness alone doesn’t tell you how strong a roofing sheet is. A corrugated sheet may be only around 1mm thick, while multiwall sheets are commonly 10mm, 16mm or more. Corrugated sheets get much of their strength from their profiled shape, while multiwall sheets get theirs from their internal structure.

So thicker generally means stronger when comparing like-for-like sheets, but you shouldn’t use thickness alone to compare corrugated and multiwall polycarbonate.

Where to next?

We hope this guide has helped you to decide on the best polycarbonate sheet to buy for your project. However, if you have any more questions, feel free to contact our award-winning customer services team on 01295 565565 or chat to us directly using the chatbox below. They will do their best to assist with any queries about roofing and roofing products you may have.

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