SPRING SAVINGS 10% off your glazing bars when you buy your polycarbonate from us! Use BAR10 at checkout.

Polycarbonate Buyers Guide

Guide to choosing your Multiwall Polycarbonate Sheets

Here at the Glazing Shop we want to help you make the right choices. If you have a question that isn't answered in the following guide, please contact us for more information on 01536 446395.

This guide looks at structured polycarbonate sheets as opposed to solid ones. Structured sheets are made from layered polycarbonate walls, and cavities (knows as flutes.) These structures give additional strength whilst keeping the weight of the sheets more manageable. They also increase thermal insulation and the thicker the sheet, and more walls and cavities it has, the more thermally insulating it is.

Polycarbonate sheets are used for a wide variety of applications. There is a large range of thicknesses and a variety of colours which offer different benefits depending on your project/application. With this in mind there are a number of things to take into consideration when looking for the right polycarbonate sheeting.

1. Sheet Thickness

Basically the thicker the sheet the stronger and more rigid it is. It can therefore achieve greater spans between supports and its impact resistance is increased. The maximum recommended unsupported spans for structured roofing polycarbonate are:

10mm polycarbonate        600mm

16mm polycarbonate        900mm

25mm polycarbonate        1050mm

35mm polycarbonate        1200mm

NB: Please bear in mind that you also need to consider any limitations of the supports and glazing bars when constructing your roof. These may require centres to be smaller.

The different thicknesses have various physical structures i.e. the number of polycarbonate walls and their design or structure changes. 

The structure of our polycarbonate sheets are as follows:


As the sheets get thicker you also have the added benefits of lower U-values. The U-value is the amount of heat transferred or conducted through a material. The lower the U-value the better the insulation performance will be.

The light transmission is also reduced as the sheet thickness increases. If you take clear polycarbonate as an example this reduces from 82% on 4mm to 50% transmission with 35mm.

For more technical information please see the specification sheets in our brochures section.

2. Application

Certain sheet thicknesses naturally suit certain applications. You wouldn’t overspend on 25mm polycarbonate sheets to glaze a greenhouse when 4mm or 6mm would do the job. Equally you couldn’t use 4mm  on a conservatory roof as you would not get the spans or insulation benefits.

Popular applications for each thickness are as follows:

4mm & 6mm Polycarbonate

These twinwall polycarbonate sheets are generally used for Greenhouse glazing. 4mm sheets and 6mm sheets are much safer and easier to handle than glass. They are also lighter weight, stronger and have better thermal insulation. They are also sometimes used internally for point of sale boards. We will cut these to the sizes you need but they can also be easily trimmed down on site.

10mm Polycarbonate

10mm twinwall polycarbonate sheets are mostly used for open structures like car ports and canopies where high degrees of thermal insulation are not required. They are best suited to those with smaller spans and centres between the glazing bars. They are a very cost effective and lightweight sheet. 


16mm Polycarbonate

16mm polycarbonate is known as triple wall as the sheet is constructed with three walls and two chambers in between. This is the most popular polycarbonate sheet thickness for carports and canopies. It is sometimes used in smaller conservatories that are generally not heated i.e. utility areas.


25mm polycarbonate

25mm polycarbonate has an 'X' Structure and is a very strong, high quality glazing material. With excellent insulation properties, it is used primarily in conservatories, orangeries & atriums. It is also a popular choice for high end canopies or commercial projects. You also have the additional colour choice of dual tints including Heatguard and Bronze Opal at this thickness.


32mm polycarbonate

Used in conservatory roofs, this is a very strong and thermally efficient sheet. In terms of performance 32mm polycarbonate falls between 25mm & 35mm.

This sheet is not so commonly used nowadays. Most people prefer the higher specification 35mm sheet which is often more cost effective. Heatguard and Bronze Opal colour choices are also available at this sheet thickness.


35mm polycarbonate

35mm polycarbonate was specifically created for use in conservatory roofs.  This is the strongest and most thermally efficient sheet in our range.

This roof sheet range has the added benefit of a wide range of colours (including Heatguard and Bronze Opal.) This allows you to tailor the amount of light and heat in your room. Depending upon its position and the level of sun it gets. 


3. Colour

When choosing the colour of your polycarbonate your first thought will probably be aesthetics. How do I want it to look? There are however, other things you will want to take into consideration.

You may want want to consider the level of light you want to allow in. You may also want to consider the level of heat you want to retain or block. The different polycarbonate sheeting colours offer varying degrees of light transmission and insulation. This range allows you, in conjunction with the sheet thickness, to really tailor the effect you are trying to achieve.

For more technical information please see the specification sheets in our brochures section.

Clear multi-wall polycarbonate

Clear multi-wall polycarbonate lets the maximum amount of light shine through. It also allows the maximum of heat to build up and is an excellent choice for darker, colder spots.

Perfect for greenhouse glazing in thinner 4mm and 6mm sheets.

Opal-tinted multi-wall polycarbonate

Opal-tinted multi-wall polycarbonate is a great all-rounder. Similar in appearance to the opacity of an opal light bulb, it allows diffused softer light through. It helps to reduce heat build-up in one area, reducing the creation of hot spots.

Its tinted appearance provides just the right amount of privacy while still maintaining a light and bright space. Often used on car ports to camouflage the leaves and debris that may fall on the roof.

Bronze-tinted multi-wall polycarbonate

Bronze-tinted multi-wall polycarbonate is good for particularly bright spots where you may want less light to pass through. It helps to reduce heat build-up, keeping rooms cooler.

Popular for wooden carport roofs or pergolas. Ideal where brown glazing bars are used

Heatguard polycarbonate

Heatguard polycarbonate is a special double extrusion with a grey outer and an opal inner. This dual tint polycarbonate is especially suited to very sunny south facing conservatories.

The outer layer reflects and repels heat helping to keep the conservatory cooler than with standard glazing. The opal interior keeps it looking light and bright. It can appear somewhat like a ceiling at night as artificial light reflects off it.

This colour option is available for 25mm, 32mm and 35mm polycarbonate sheets.

Bronze Opal polycarbonate

Bronze Opal polycarbonate is again a double extrusion or dual tint sheet with a bronze outer and an opal inner. Suited to sunny conservatories, the outer layer reflects light and repels heat to a slightly lesser degree than Heatguard. It has 8% light transmission as opposed to the 7% in Heatguard.

The opal interior again keeps it looking light & bright as artificial light is bounced around the room. It again gives a ceiling like appearance at night. This polycarbonate sheeting is a more popular choice for brown conservatories. These dual tint sheets are available in 25mm, 32mm and 35mm polycarbonate sheet thicknesses.

For your peace of mind, all of our multiwall polycarbonate carries a Ten Year Limited Manufacturers Warranty. This guards against discolouration, loss of light transmission and/or loss of strength due to weathering. For full warranty information please choose from the relevant links below.

Marlon st Polycarbonate Sheet Warranty

Sunlite Polycarbonate Sheet Warranty