How to Apply Polycarbonate Breather Tape & Foil Tape
Applying breather tape and foil tape correctly is one of the most important steps when installing a polycarbonate roof. Although these tapes are small and often overlooked, they play a vital role in protecting the internal flutes of the sheet and helping your roof perform correctly for many years.
Foil tape seals the top of the sheet, preventing dirt, dust and insects from entering the flutes. Breather tape is fitted to the bottom of the sheet, allowing condensation to drain naturally while still helping to keep insects and debris out.
In this guide, we'll explain where each tape should be fitted, why both tapes are needed and the correct installation method to help keep your polycarbonate roof clean, dry and performing at its best.
Before You Begin
Before applying any sealing tape, make sure your polycarbonate sheets have been cut to their final size and all swarf has been removed from the internal flutes. Small plastic shavings left inside the sheet can trap moisture and dirt, so it's important to clean them out before sealing the ends.
Take a moment to identify the top and bottom of each sheet. The side with the UV protective layer should always face upwards once installed, making it much easier to identify which edge will become the top and which will become the bottom.
Before applying either tape, ensure the ends of the sheet are clean, dry and free from dust. Sealing tape adheres best to a clean surface, helping to create a long-lasting seal that protects the internal flutes.
Finally, make sure you have both types of tape ready before you begin. Although they may look similar, foil tape and breather tape perform completely different jobs and should never be fitted interchangeably.
Understanding the Difference Between Foil Tape & Breather Tape
Although foil tape and breather tape are often supplied together, they perform two completely different jobs. Using both tapes correctly is essential for protecting your polycarbonate sheets and helping them perform as intended.
Foil Tape
Foil tape is always fitted to the **top** of the polycarbonate sheet. Its purpose is to create a complete seal across the open flutes, preventing dirt, dust, insects and moisture from entering the sheet from above.
Because the top of the roof is exposed to rainfall, leaves and airborne debris, creating a fully sealed barrier at this end of the sheet is essential for keeping the internal flutes clean.
Breather Tape
Breather tape is always fitted to the bottom of the polycarbonate sheet. Unlike foil tape, it isn't completely sealed. Instead, it contains a special breathable membrane that allows condensation trapped inside the sheet to escape while still helping to prevent insects and dirt from entering the flutes.
This controlled airflow is important because small amounts of condensation can naturally form inside multiwall polycarbonate sheets as temperatures change. Breather tape allows this moisture to drain away rather than becoming trapped inside the sheet.
Why Both Tapes Are Needed
Foil tape and breather tape are designed to work together as a complete sealing system. Foil tape protects the top of the sheet from contamination, while breather tape allows the bottom of the sheet to breathe and drain correctly.
Using only one type of tape, or fitting them in the wrong positions, can reduce the performance of the roofing system and may lead to dirt, insects or trapped moisture inside the sheet over time.
Step 1 – Apply the Foil Tape
The first stage of sealing your polycarbonate sheet is to apply the foil tape to the top edge of the sheet. This creates a complete barrier that prevents dirt, dust, insects and moisture from entering the internal flutes from above.
Before applying the tape, make sure the end of the sheet is clean, dry and free from dust. The tape will only bond correctly if it is applied to a clean surface.
Starting at one side of the sheet, carefully position the foil tape so it completely covers every flute. Press the tape firmly onto the end of the sheet, working steadily across its full width to ensure a continuous seal.
Once the tape has been applied, run your finger or a clean plastic applicator firmly along its entire length to ensure it is fully bonded. Pay particular attention to the outer edges of the sheet, making sure there are no gaps where dirt or insects could enter.
The foil tape should completely seal the top edge of the sheet before the end closure is fitted.
Step 2 – Apply the Breather Tape
Once the foil tape has been fitted to the top of the sheet, the next step is to apply breather tape to the bottom edge.
Unlike foil tape, breather tape is specially designed to allow condensation inside the polycarbonate sheet to escape while still helping to prevent dirt, dust and insects from entering the flutes. This allows the sheet to breathe naturally and helps keep the internal chambers cleaner over time.
Before applying the tape, make sure the bottom edge of the sheet is clean, dry and free from dust. Position the breather tape so it completely covers the open flutes, ensuring there are no gaps along the width of the sheet.
Press the tape firmly into place using even pressure across its entire length. Avoid stretching the tape during installation, as this can affect how it sits on the sheet and reduce the quality of the seal.
Once fitted, check that every flute is covered and that the tape is fully bonded to the sheet. The breather tape should then be protected by fitting the PolycarbonateX sheet end closure over the edge of the sheet.
When installed correctly, the breather tape allows condensation to drain naturally while protecting the inside of the sheet from contamination, helping your polycarbonate roof remain cleaner and perform as intended for many years.
Check Your Work Before Installing the Sheets
Before fitting the polycarbonate sheets into the glazing bar system, take a few moments to inspect the sealing tapes. Correctly applied tape is essential for protecting the internal flutes and ensuring the roof performs as intended.
Check that the foil tape completely covers every flute along the top edge of the sheet. There should be no gaps, wrinkles or areas where the tape has lifted away from the polycarbonate.
Next, inspect the breather tape on the bottom edge. It should be firmly bonded across the full width of the sheet, covering every flute without being stretched or damaged during installation.
Finally, make sure the PolycarbonateX sheet end closures have been fitted over both tapes. The end closures protect the tapes from damage while providing a neat, professional finish.
Taking a few minutes to carry out these final checks before installing the sheets can help prevent problems later and gives you confidence that your roofing system has been prepared correctly.
Common Sealing Tape Installation Mistakes
Although applying sealing tape is a simple task, small mistakes can affect the long-term performance of your polycarbonate roof. Here are the most common issues we see and how to avoid them.
Fitting the Tapes the Wrong Way Around
Foil tape should always be fitted to the top of the sheet, while breather tape should always be fitted to the bottom. Reversing the tapes can prevent condensation from draining correctly and may allow dirt or moisture to become trapped inside the flutes.
Applying Tape to Dirty or Wet Sheets
Sealing tape bonds best to clean, dry polycarbonate. Applying tape to dusty or damp surfaces can reduce adhesion and increase the risk of the tape lifting over time.
Leaving Gaps Over the Flutes
The tape should completely cover every flute across the width of the sheet. Even small gaps can allow dirt, insects and moisture to enter the internal chambers.
Stretching the Breather Tape
Breather tape should be applied naturally without pulling or stretching it. Stretching the tape can affect how it sits on the sheet and reduce the quality of the seal.
Forgetting the End Closures
Sealing tape should always be protected by fitting the correct PolycarbonateX sheet end closures. The end closures help protect the tape from damage and provide a neat, professional finish.
Frequently asked questions
Why do I need two different types of tape?
Foil tape and breather tape perform different jobs. Foil tape seals the top of the sheet to prevent dirt and insects entering the flutes, while breather tape allows condensation to drain naturally from the bottom of the sheet.
Can I use foil tape on both ends of the sheet?
No. The bottom of the sheet should always use breather tape so that condensation can escape from the internal flutes.
Can I use breather tape on the top of the sheet?
No. Breather tape is only designed for the bottom edge of the sheet. The top should always be sealed with foil tape.
Do I apply the tape before fitting the end closures?
Yes. The sealing tapes should always be applied first, followed by the PolycarbonateX sheet end closures.
Should I remove the protective film before applying the tape?
Remove only enough protective film to expose the edge of the sheet where the tape will be applied. Leave the rest of the protective film in place until the roof has been installed to help prevent scratches.
What happens if I fit the tapes the wrong way around?
The sheet may not drain condensation correctly, increasing the risk of moisture, dirt and insects becoming trapped inside the flutes. If the tapes have been fitted incorrectly, they should be replaced before the sheets are installed.
How long do the sealing tapes last?
When installed correctly and protected by the PolycarbonateX sheet end closures, quality sealing tapes are designed to provide many years of reliable performance as part of the complete roofing system.
Can I replace damaged sealing tape?
Yes. If the tape becomes damaged, contaminated or starts to lift, it should be removed and replaced before the roofing sheet is installed.
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.