How to Install Polycarbonate Fixing Buttons
Polycarbonate fixing buttons provide a simple and effective way of securing multiwall polycarbonate sheets directly to timber rafters. When installed correctly, they hold the sheet firmly in place while still allowing it to expand and contract naturally as temperatures change.
Unlike glazing bar systems, fixing buttons secure the sheet through pre-drilled fixing points using a screw, rubber sealing washer and PVC cover cap. This makes them a popular solution for smaller roofing projects, cold frames, shelters and simple timber-framed structures.
In this guide, we'll explain how PolycarbonateX fixing buttons work, how to install them correctly and the common mistakes to avoid, helping you achieve a secure, weather-resistant installation without damaging your polycarbonate sheets.
Before You Begin
Before installing PolycarbonateX fixing buttons, make sure your roof structure has been completed and the polycarbonate sheets have already been cut to their final size. Any swarf should be removed from the internal flutes, the correct sealing tapes should be applied and the sheet end closures should already be fitted.
This guide is written specifically for PolycarbonateX fixing buttons used to secure multiwall polycarbonate sheets directly onto timber rafters. Unlike glazing bar systems, fixing buttons secure the sheet through individual fixing points, making correct positioning and drilling especially important.
Before fitting the fixing buttons, check that every timber rafter is straight, securely fixed and provides adequate support beneath the sheet. It's also important to confirm the recommended fixing positions before drilling any holes.
Finally, remember that polycarbonate expands and contracts as temperatures change. The fixing holes must always be drilled slightly larger than the screw diameter to allow the sheet to move naturally. This is one of the most important parts of the installation and helps prevent unnecessary stress on the sheet once it's installed.
Understanding How Polycarbonate Fixing Buttons Work
Polycarbonate fixing buttons are designed to secure multiwall polycarbonate sheets directly to timber rafters without restricting the natural movement of the sheet. Although each fixing button is made up of just a few components, every part has an important role in creating a secure, weather-resistant fixing.
PVC Cover Cap
The white PVC cover cap provides a neat, professional finish while protecting the screw head from the weather. Once the fixing has been tightened correctly, the cap clips into place to help keep water and dirt away from the fixing.
Rubber Sealing Washer
Beneath the cover cap is a flexible rubber sealing washer. As the fixing is tightened, the washer compresses against the surface of the polycarbonate sheet to create a weather-resistant seal. It should be compressed just enough to form the seal without crushing the sheet.
Fixing Screw
The screw passes through the centre of the fixing button and into the timber rafter below, securing the sheet firmly to the roof structure. Always use the recommended screw length for your roof construction to ensure a secure fixing.
Oversized Fixing Hole
One of the most important parts of the installation is the oversized fixing hole. The hole drilled through the polycarbonate sheet should always be larger than the diameter of the screw. This allows the sheet to expand and contract naturally as temperatures change while remaining securely fixed to the roof.
Together, these components create a strong, weather-resistant fixing that holds the sheet securely while allowing the natural thermal movement required by multiwall polycarbonate roofing.
Step 1 – Mark & Drill the Fixing Holes
Before drilling any holes, position the polycarbonate sheet on the roof and check that it is correctly aligned with the supporting timber rafters. Once you're happy with its position, mark the centre of each fixing point directly above the rafters.
Always use a sharp drill bit suitable for plastics and support the sheet properly while drilling. Drill slowly and allow the drill bit to cut cleanly through the sheet without forcing it, as excessive pressure can damage the polycarbonate.
One of the most important parts of the installation is drilling an oversized fixing hole. The hole should always be larger than the diameter of the fixing screw to allow the sheet to expand and contract naturally as temperatures change. If the hole is drilled too small, the sheet can become restricted, increasing the risk of stress cracking or distortion over time.
After drilling, remove any swarf or plastic shavings from around the hole and from inside the sheet flutes before continuing with the installation. Leaving debris behind can affect the appearance of the roof and reduce the effectiveness of the sealing system.
Once every fixing hole has been drilled and cleaned, the sheet is ready for the fixing buttons to be installed.
Step 2 – Install the Fixing Buttons
With all of the fixing holes drilled, you're ready to install the PolycarbonateX fixing buttons.
Place a fixing button over each pre-drilled hole, ensuring the rubber sealing washer sits flat against the surface of the polycarbonate sheet. Insert the fixing screw through the centre of the button and into the timber rafter below.
Using a screwdriver or cordless drill set to a low torque setting, tighten the screw until the rubber sealing washer forms a weather-resistant seal against the sheet. The washer should compress slightly, but it should never be crushed or forced hard against the polycarbonate.
Avoid over-tightening the fixing. Polycarbonate sheets need to expand and contract as temperatures change, and excessive pressure can place unnecessary stress on the sheet around the fixing hole. The sheet should remain secure while still being free to move naturally within the oversized hole.
Repeat the process for each fixing button, checking regularly that the sheet remains flat against the roof structure without distortion. Once every fixing has been installed, clip the white PVC cover caps firmly into place to protect the screw heads and provide a neat, professional finish.
Before considering the installation complete, check that every fixing button sits evenly on the sheet, every cover cap is securely clipped into position and the sheet remains flat with no signs of stress around the fixing holes.
Common Fixing Button Installation Mistakes
Although PolycarbonateX fixing buttons are quick and easy to install, incorrect installation can reduce the performance and lifespan of your polycarbonate roof. Here are the most common mistakes we see and how to avoid them.
Drilling the Hole Too Small
The fixing hole should always be larger than the diameter of the fixing screw. Polycarbonate expands and contracts as temperatures change, and an oversized hole allows this natural movement to occur without placing unnecessary stress on the sheet.
Over-Tightening the Screw
The rubber sealing washer only needs to compress enough to create a weather-resistant seal. Tightening the screw too much can distort the sheet, crush the washer and increase the risk of stress cracking around the fixing point.
Drilling Too Close to the Edge of the Sheet
Fixing holes should be positioned with sufficient clearance from the edge of the sheet. Drilling too close to the edge can weaken the sheet and increase the likelihood of cracking during installation or thermal movement.
Leaving Plastic Swarf Around the Hole
After drilling, always remove any plastic shavings from the surface of the sheet and from the internal flutes. Leaving swarf behind can affect the appearance of the roof and may prevent the sealing washer from sitting correctly.
Forgetting to Fit the PVC Cover Cap
Once the fixing has been tightened correctly, always clip the white PVC cover cap into position. The cap protects the screw head from the weather while giving the installation a clean, professional appearance.
Taking your time during installation and checking each fixing as you work will help ensure your PolycarbonateX roofing system remains secure, weather-resistant and able to accommodate natural thermal movement for many years.
Frequently asked questions
What are polycarbonate fixing buttons used for?
Polycarbonate fixing buttons are used to secure multiwall polycarbonate sheets directly onto timber rafters. They provide a weather-resistant fixing while allowing the sheet to expand and contract naturally.
Why does the fixing hole need to be oversized?
Polycarbonate naturally expands and contracts as temperatures change. An oversized hole allows this movement to occur without placing stress on the sheet around the fixing point.
How tight should the fixing button be?
The screw should be tightened until the rubber sealing washer forms a weather-resistant seal against the sheet. It should never be tightened so much that the washer is crushed or the sheet becomes distorted.
Can I use ordinary screws without fixing buttons?
No. Polycarbonate fixing buttons are designed to distribute pressure evenly across the sheet while providing a weather-resistant seal. Ordinary screws alone can damage the sheet and are not recommended.
Can fixing buttons be used with glazing bars?
No. PolycarbonateX fixing buttons are designed for roofing systems where the sheets are fixed directly to timber rafters. Rafter-supported glazing bar systems secure the sheets using glazing bars instead.
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.