How to Install Polycarbonate Sheet End Closures
Polycarbonate sheet end closures are a small but essential part of any polycarbonate roofing system. They protect the open ends of the sheets, help keep the sealing tapes securely in place and provide a neat, professional finish.
When installed correctly alongside foil tape and breather tape, end closures help prevent dirt, insects and debris from entering the sheet flutes while still allowing moisture to drain naturally from the bottom of the sheet.
In this guide, we'll explain how to install PolycarbonateX sheet end closures correctly, where they should be fitted and the common mistakes to avoid to ensure your roof performs reliably for many years.
Before You Begin
Before fitting your sheet end closures, make sure the polycarbonate sheets have already been cut to their final size and any swarf has been removed from the internal flutes. Taking a few extra minutes to prepare the sheets correctly will help ensure the roofing system performs as intended.
This guide is written specifically for PolycarbonateX polycarbonate sheet end closures, which fit over the open ends of multiwall polycarbonate sheets. They work together with foil tape and breather tape to protect the sheet flutes from dirt, insects and moisture while allowing condensation to drain naturally.
Before starting, check that you have the correct end closures for your sheet thickness. End closures are manufactured to fit specific sheet sizes, so using the correct profile is essential for a secure fit.
It's also important to identify the top and bottom of every sheet before fitting the tapes and end closures. The top edge should always receive foil tape, while the bottom edge should always receive breather tape. Once the tapes have been applied, the end closures can be pushed fully onto the sheet to protect the tapes and provide a neat, professional finish.
Understanding How Sheet End Closures Work
Polycarbonate sheet end closures do much more than simply finish the edge of your roof. They play an important role in protecting the internal structure of the sheet and helping the roofing system perform correctly over time.
Multiwall polycarbonate sheets contain hollow flutes that run the full length of the sheet. If these open ends are left unprotected, dirt, insects and debris can enter the flutes, affecting both the appearance and performance of the roof.
The end closure fits securely over the top and bottom of the sheet, covering the sealing tape and protecting the exposed edge from everyday wear and weather.
At the top of the roof, the end closure sits over the foil tape, creating a durable barrier that helps prevent dirt and moisture entering the sheet.
At the bottom of the roof, the end closure protects the breather tape while still allowing condensation inside the sheet to drain naturally. This helps keep the internal flutes cleaner and reduces the risk of moisture becoming trapped within the sheet.
Although it's a simple component, the end closure plays an important part in creating a tidy, weather-resistant roofing system that's designed to last.
Step 1 – Fit the End Closures
Before fitting the end closures, check that the correct sealing tape has already been applied to both ends of the polycarbonate sheet. The top of the sheet should be sealed with foil tape, while the bottom should be sealed with breather tape. These tapes protect the internal flutes and are an essential part of the roofing system.
Once the tapes have been fitted, position the correct PolycarbonateX end closure over the edge of the sheet. The profile should slide evenly over both faces of the sheet, covering the sealing tape completely and forming a neat, secure finish.
Push the end closure fully onto the sheet until it is seated correctly along its entire length. It should fit snugly without leaving gaps, but it should never be forced into position.
Repeat the process for both the top and bottom of every polycarbonate sheet, checking that the correct end closure has been fitted to the correct sheet thickness before continuing with the roof installation.
Step 2 – Check the Fit
Once the end closure has been fitted, take a few moments to check that it has been installed correctly. A properly fitted end closure should sit evenly across the full width of the sheet, with no gaps between the profile and the polycarbonate.
Run your hand gently along the length of the end closure to make sure it is fully seated. If one section has not been pushed fully into place, remove the profile carefully and refit it rather than forcing it.
Check that the foil tape or breather tape is completely covered by the end closure. The tape should not be visible once the profile has been correctly installed, as the end closure is designed to protect it from the weather while giving the sheet a clean, professional finish.
Finally, inspect the end of the sheet to make sure there are no sharp edges, trapped debris or damage to the sealing tape. If everything looks correct, the sheet is now ready to be installed into the glazing bar system.
Common Sheet End Closure Installation Mistakes
Although sheet end closures are quick and easy to install, fitting them incorrectly can affect the appearance and long-term performance of your polycarbonate roof. Here are the most common mistakes we see and how to avoid them.
Fitting the End Closure Before the Sealing Tape
The foil tape or breather tape should always be applied before fitting the end closure. The end closure is designed to protect the tape, not replace it. Without the correct sealing tape, dirt, insects and moisture can enter the sheet flutes.
Using the Wrong End Closure
End closures are manufactured to suit specific polycarbonate sheet thicknesses. Always check that the profile matches your sheet before installation. A closure that's too small won't fit correctly, while one that's too large won't provide adequate protection.
Not Pushing the End Closure Fully Into Position
The end closure should be fitted evenly across the full width of the sheet until it is fully seated. If part of the profile is left loose, it may not protect the sealing tape correctly and can affect the finished appearance of the roof.
Damaging the Sealing Tape During Installation
When sliding the end closure onto the sheet, take care not to pull, crease or tear the sealing tape. If the tape becomes damaged, it should be replaced before the roofing sheet is installed.
Forgetting Which End of the Sheet Is the Top
The top edge of the sheet should always have foil tape beneath the end closure, while the bottom edge should always have breather tape. Mixing these up can affect the way condensation drains from the sheet.
Frequently asked questions
Do I need sheet end closures?
Yes. Sheet end closures help protect the sealing tapes, improve the appearance of the roof and provide additional protection to the exposed ends of the polycarbonate sheets.
Do end closures stop water entering the sheet?
End closures work together with foil tape and breather tape. The tapes provide the seal, while the end closures protect the tapes and provide a neat, durable finish.
Can I fit the end closures before applying the tape?
No. The sealing tape should always be applied first, followed by the end closure.
Do I need an end closure at both ends of the sheet?
Yes. A correctly installed polycarbonate sheet should have an end closure fitted to both the top and bottom edges.
Can I reuse old end closures?
If the existing end closures are damaged, loose or distorted, we recommend replacing them when fitting new polycarbonate sheets to ensure the best possible finish and performance.
Do end closures fit every sheet thickness?
No. End closures are designed for specific sheet thicknesses. Always select the correct profile for your polycarbonate sheets.
Should the end closure be sealed with silicone?
No. PolycarbonateX sheet end closures are designed to fit securely over the sheet and sealing tape without the need for silicone. Using silicone can interfere with drainage and make future maintenance more difficult.
How do I know if the end closure is fitted correctly?
A correctly fitted end closure will sit evenly across the full width of the sheet, completely cover the sealing tape and fit snugly against both faces of the polycarbonate sheet.
Need More Help?
Still unsure which sheet thickness is right for your project? Our UK team can help you check your requirements, calculate the materials you need or visualise how your finished roof could look.