How to Install Polycarbonate Roofing [The Right Way]

Polycarbonate roofing is one of the most popular choices for conservatories, carports, pergolas, greenhouses, and garden rooms in the UK.

It’s lightweight, durable, UV-resistant, and lets in plenty of natural light—making it a great alternative to glass or traditional roofing systems. Polycarbonate roofing sheets are versatile and effective in providing protection from the elements while allowing natural light to penetrate into various spaces such as conservatories, patios, and greenhouses.

But how do you install polycarbonate roofing properly?

At Roofing Newcastle, we’ve installed hundreds of polycarbonate roofs across the North East. In this guide, we’ll show you how to install polycarbonate roofing step by step, with all the tools, materials, and know-how you’ll need to get a clean, long-lasting finish.

What You’ll Need

Before you begin, gather the following tools and materials:

Tools:

• Safety Glasses
• Tape measure
• Cordless drill or screwdriver
• Fine-tooth saw or jigsaw (if cutting panels)
• Spirit level
• Marker pen
• Safety goggles and gloves

Materials:

• Polycarbonate roofing sheets (solid or multiwall)
• Glazing bars or H profiles
• End caps
• Fixing buttons or screws with rubber washers
• Closure tape (breathable or anti-dust)
• Flashing tape (if sealing to walls)
• Wall flashing or apron flashing (if required)
• Glazing system (to accommodate thermal expansion and contraction)

Tip: Make sure your sheets are UV-protected on one side, and that side faces outward (check the printed film).

Preparing for Installation

Before starting the installation process, it’s essential to prepare the site and ensure you have all the necessary tools and materials. Begin by clearing the area of any debris and ensuring the roof surface is clean and dry. Check for any damage or weaknesses in the structure that might affect the installation. Reading and following the manufacturer’s instructions for specific installation requirements is crucial to avoid any mistakes.

Safety should be a top priority. Wear safety glasses and gloves to protect yourself from potential hazards during the installation process. Use a sturdy ladder or scaffolding to access the roof safely. Additionally, check the weather forecast and avoid installing polycarbonate roofing sheets during wet or windy conditions to ensure a smooth and safe installation process.

Measuring and Planning

Measuring and planning are critical steps in the installation process. Start by measuring the roof area carefully to ensure accurate cuts and plan the layout of the polycarbonate sheets. Take into account any overlaps or gaps that might be necessary. Creating a sketch of the layout can be incredibly helpful as a guide during the installation.

Consider the size and shape of your roof when planning the layout, and measure the polycarbonate sheets to ensure they fit the roof area perfectly. Plan for any necessary cuts or modifications to the sheets, and double-check all measurements and the layout before starting the installation process. This careful planning will help avoid mistakes and ensure a smooth installation.

Step-by-Step: How to Install Polycarbonate Roofing

Step 1: Prepare the Roof Structure

Polycarbonate roofs require a strong, stable framework—usually made from timber or aluminium.

Ensure the rafters or beams are:

• Properly spaced (typically 600mm centres for 10mm twinwall polycarbonate)
• Level and securely fixed
• Sloped for water drainage (minimum 5° pitch recommended)

A gentle slope helps water run off and prevents pooling on the sheets.

Step 2: Measure and Cut the Polycarbonate Roofing Sheets

Measure the span of your roof and cut the polycarbonate roofing sheet to size.

• Use a fine-tooth saw or jigsaw to make clean cuts
• Cut with the protective film still on the sheet
• Remove any dust or debris from the flutes before installation
• Seal cut ends with closure tape:
• Breathable tape on the bottom (to allow moisture to escape)
• Foil tape on the top (to keep dust and insects out)

Step 3: Position the Sheets

Lay your sheets across the rafters with the flutes running vertically (in the direction of the slope). This helps water drain properly. Proper positioning of the sheets ensures optimal light transmission, which is beneficial for structures like greenhouses.

• Leave a 2–3mm expansion gap between sheets
• Allow 5mm overhang at the gutter end
• Make sure the UV-protected side is facing up

Step 4: Fix the Sheets in Place

Use glazing bars or H-section profiles to join the polycarbonate panels and hold them securely in place.

• Glazing bars should be fixed to rafters using screws
• Fixing buttons or screws with rubber washers can be used to secure sheets independently
• Don’t overtighten—leave room for thermal expansion
• Always pre-drill holes in the polycarbonate to prevent cracking

Important: Only drill in the flat sections between the flutes—never through the flutes themselves.

Step 5: Fit End Caps and Closure Profiles

Seal the edges of the polycarbonate roof sheets using:

• End caps for neatness and water run-off
• Closure profiles at the bottom of the sheet to prevent insects and debris entering the flutes

This step helps extend the life of your roof and keeps it looking tidy.

Step 6: Install Flashing (If Needed)

If your roof connects to a wall (e.g. conservatory or lean-to), you’ll need to install wall flashing:

• Use aluminium or lead flashing to seal the join
• Apply flashing tape underneath for added waterproofing
• Seal any exposed joints with appropriate silicone or sealant

This prevents water ingress where the roof meets the house or wall. While metal roofing is known for its durability, polycarbonate roofing offers benefits such as light transmission and impact resistance.

Tips for Proper Installation

To ensure a successful installation, follow these tips:

• Always adhere to the manufacturer’s instructions for specific installation requirements.
• Use the correct fasteners and materials for the job to ensure a secure fit.
• Ensure a watertight seal between the flashing and trim to prevent leaks.
• Regularly inspect the roof for any signs of damage or wear, and address any issues promptly to maintain the integrity of the roof.
• Use a silicone sealant to seal gaps and joints effectively.
• Apply a UV-resistant coating to the polycarbonate sheets to prevent discolouration and degradation over time.

By following these tips, you can ensure a successful installation and extend the lifespan of your polycarbonate roofing sheets, keeping your structure protected and looking great for years to come.

Maintenance Tips

Once installed, polycarbonate roofing is low-maintenance, but here’s how to keep it in top shape:

• Clean twice a year with warm water and mild soap
• Avoid abrasive sponges or harsh chemicals
• Check seals and fixings regularly
• Remove debris and leaves from gutters and edges

Can You Install Polycarbonate Roofing Yourself?

Yes—many homeowners install polycarbonate sheet roofing as a DIY project, especially on smaller structures like pergolas or greenhouses.

However, for larger or more complex roofs—like conservatories or carports—it’s often better to hire a professional.

At Roofing Newcastle, we offer professional installation for polycarbonate roofing systems of all sizes, ensuring they’re secure, leak-free, and built to last.

Final Thoughts

So—how do you install polycarbonate roofing?

With the right tools, solid planning, and a few careful steps, it’s a straightforward process. You’ll end up with a lightweight, weather-resistant, and attractive roof that lasts for years. When using thinner sheets, ensure closer support spacing to avoid sagging and ensure a stable installation.

But if you’d prefer peace of mind with professional installation, get in touch with Roofing Newcastle today. We’ll help you choose the right polycarbonate system and install it safely, efficiently, and to the highest standards.