How Thick Should My Polycarbonate Sheets Be?

Roof Sheets
How Thick Should My Polycarbonate Sheets Be?

Polycarbonate is a highly versatile roofing material that boasts durability, longevity, and resilience in a range of environments. Having exploded in popularity over the last couple of decades, thanks to its affordability coupled with a straightforward installation process, it can be found on thousands of lean-tos, greenhouses, and outbuildings across the country.

However, there are a few things to know about polycarbonate roof sheets to get the most out of utilising them in your project. One of the most crucial is understanding the importance of sheet thickness. This guide aims to help make the decision of choosing the correct thickness a little simpler. We’ll look at some of the thickness options available and the best choice for some of the most common projects that these sheets are used for.


What Thicknesses Can Polycarbonate Sheets Come In?

Let’s start by having a look at the main thicknesses available. There are several different ones to choose from, ranging from very thin to extremely thick, with greater thicknesses utilising features such as internal walls or chambers that help to make them robust and resilient while allowing them to remain lighter in weight.

Below are the most common thickness options available. Note that the majority of manufacturers will produce sheets in these thicknesses to ensure compatibility with other products and accessories.

  • 4mm – 6mm range (thin)
  • 10mm – 16mm range (medium)
  • 25mm – 35mm range (thick)

Why Is Thickness So Important When It Comes to Polycarbonate Sheeting?

Polycarbonate is popular due to its relative strength when compared to cost and ease of installation. However, if the wrong thickness is used, problems can happen. As a rule of thumb, the larger the project and the more complex the build, the thicker the sheeting will need to be.

Failing to adhere to thickness requirements may well result in damage to the roof or the building as a whole in the long run. Certain thicknesses may also be the only products that possess or lack certain features. For example, certain dimensions may boast UV-resistant properties – this is a must for conservatories but may not be needed when building a greenhouse.

What Builds Require Slim Sheets?

4mm and 6mm are the most common examples of slim polycarbonate sheets. They are very flexible and can be cut with simple tools such as knives. They are simply too thin to be used effectively on larger exterior structures but are ideal for use on indoor projects in particular.

A popular use for these sheets is when replacing broken or damaged interior glazing, particularly those found on doors and interior windows between rooms and/or corridors. The simple yet effective sheets allow virtually the same amount of light in and are also available with other features such as opaque surfaces and added UV resistance. 

You can also use these slimmer sheets when building or renovating a greenhouse. Bear in mind that greenhouse glass requires UV-friendly rays or else your plants won’t grow properly. It is vital for projects like this that you check the properties and features of your glazing beforehand.

What Builds Require Medium Sheets?

10mm – 16mm is the most common medium sheet size range. It’s perfect for use on a wide range of structures, with lean-to’s one of the most common. These structures need a roof that is strong but not too heavy, which rules out a lot of roofing alternatives. Even some sheeting types will be unsuitable if your lean-to is quite small and lightly built.

Polycarbonate, on the other hand, is resilient and long-lasting, without any of the more advanced installation techniques required when it comes to other roofing materials. They are the perfect match for lean-to’s, offering shelter from the worst of the elements including rain, snow, and hail, while still allowing the contents within the lean-to to remain in an exterior environment. 

What Builds Require Thick Sheets?

Thicker sheets should most certainly be used on structures where frequent residential use is expected. The most common example would be in a conservatory. These days, there are variations of 25mm, 32mm, and 35mm sheets that have been designed specifically for use on conservatory roofs.

While it is possible, as with smaller thicknesses, to use polycarbonate sheets as a ‘fix’ to replace broken or damaged glass panels, it is recommended to keep conservatory and similar roofs as consistent as possible. If you plan to use polycarbonate on your conservatory roof, then the whole roof should ideally be replaced and fitted with relevant accessories.



4mm – 6mm (thin)

Interior glazing, greenhouses & other smaller garden buildings

10mm – 16mm (medium)

Lean to’s & carports

25 – 35mm (thick)

Conservatories, extensions & commercial settings

How Thick Do Polycarbonate Sheets Need to be For Greenhouses?

Polycarbonate is the ideal material for greenhouses. They are strong and durable, but still lightweight enough to make installation simple whilst allowing a good deal of light transmission. But is there an ideal thickness?

Well, it largely depends on your type of greenhouse. The first factor to keep in mind is how much weight the frame of your greenhouse can hold – this will typically also be directly proportional to the size of the greenhouse. The thicker the frame the thicker the sheets can be. 

Next, the thickness of the sheets will depend on whether you are opting for solid sheets or twinwall. The key difference between the two, of course, is their weight and inherent strength. Solid sheets, being heavier, will need to be thinner – with recommended sheets being 3 – 6mm. As for twinwall, this can be extended to 10mm under the right circumstances.

On average, however, 6mm is the go-to. This size of the sheet is a mid-range of equal parts strength and low weight. Most 6mm sheets also boast impressive impact resistance. Essential for protecting your plants from hail and other falling debris.

What If I’m Replacing a Glass Panelled Polycarbonate Roof?

If you are doing a simple swap over, replacing damaged glass panes with polycarbonate, then choosing thickness is simple. Just match your polycarbonate to your glass. If your panes were originally 6mm then 6mm polycarbonate will be your best bet. This will save you significantly more time and money.

What Colour Polycarbonate is Best for Greenhouses?

The colour of your sheet is the biggest contributing factor the light transmission, inarguably the most important aspect when building a greenhouse. As you might expect, clear polycarbonate is what most would recommend – offering the most transparency which all types of pants and vegetables will need.

However, for certain plants like spider plants, ferns and bamboo, which require less light to grow you may find that swapping out some of your clear sheets for shad

Is Thicker Polycarbonate Harder to Install?

As you may well be assuming, thicker polycarbonate tends to be larger, and thus more cumbersome when it comes to handling. In short, yes – thicker sheets are usually harder to install than thinner ones. However, this difference will most likely prove a lot less noticeable than you may think.

This is because thicker polycarbonate sheets usually utilise a multiwall build. This unique design can be seen at the cross-section of your polycarbonate sheet, where you’ll find multiple ‘chambers’ between the two (or three) flat faces on either side of your sheet.

This sandwich-like design uses more flat surfaces with additional chambers, resulting in greater thickness. It also, however, leaves a lot of air and space within the sheet, making it more hollow and thus lighter. Overall, while you may need longer, more specialised fixings (most of which should be available under the same brand as your sheets), there shouldn’t be too much more involved in installing your thicker sheets successfully.

Final Thoughts

Polycarbonate sheets benefit from being one of the most versatile roofing materials available, but as you will hopefully now be aware, the thickness of these sheets is incredibly important and will have an impact on the durability and longevity of the roof they are used on.

We hope this guide has helped you in figuring out the right polycarbonate sheet thickness for you. However, if you are still unsure it is always better to play it safe and opt for thicker sheets. Whilst they can be more difficult to handle, they also provide the most protection over the longest lifespans.

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 help assist with any queries about roofing and roofing products you may have.

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