Common Polycarbonate Roofing Questions

Accurate measurements are one of the most important parts of ordering polycarbonate roofing. Measure the finished roof area carefully, including the overall width and the slope length from the wall towards the gutter edge.

Always measure the actual roof structure rather than relying on old measurements, drawings or estimates. This helps ensure the correct sheet sizes and accessories are ordered first time.

Before ordering, you will usually need:

• Roof width
• Roof slope length
• Required sheet thickness
• Sheet colour
• Number of sheets required
• Glazing bar and accessory requirements

Having these details available will make it much easier to select the correct products for your project.

Yes. Polycarbonate sheets can be supplied in custom sizes where standard sheet dimensions are not suitable for your roof.

When ordering cut-to-size sheets, always provide accurate measurements and consider how the sheets will fit within the glazing system, including allowances for glazing bars, flashings and thermal movement.

This depends on your roof dimensions, available sheet sizes and the installation method being used.

Using fewer sheets can reduce the number of joints, but larger sheets must still be suitable for handling, installation and allowing for natural expansion and contraction.

Incorrect measurements can result in sheets or accessories not fitting correctly.

Before ordering, always double-check measurements and make sure you understand how the roofing system is assembled.

Yes. Many homeowners and installers successfully fit polycarbonate roofing systems themselves when the correct materials and installation methods are followed.

The key factors are accurate measurements, correct sheet orientation, suitable accessories and allowing for natural expansion and contraction.

The UV protected side of the sheet must face upwards towards the sky.

Most multiwall polycarbonate sheets have protective film markings to identify the correct side before installation. Installing the sheet the wrong way around can reduce its long-term performance and lifespan.

Yes. Polycarbonate naturally expands and contracts as temperatures change.

The roofing system must allow for this movement by using suitable glazing bars, fixings and installation methods. Restricting thermal movement can place unnecessary stress on the sheets.

No. Polycarbonate sheets are not designed to support body weight and should never be walked on.

Always use suitable access equipment and follow safe working practices when installing roofing materials.

Yes. A complete polycarbonate roofing system normally requires suitable glazing bars, fixing methods, sealing tapes, end closures and flashings depending on the design of the roof.

Using the correct accessories helps ensure the roof remains secure, weather resistant and performs correctly over time.

A complete polycarbonate roofing system normally requires more than just the sheets themselves.

Depending on the design of your roof, you may need glazing bars, fixing buttons, sealing tapes, end closures, flashings and other finishing components to ensure the roof is secure and weather resistant.

Glazing bars are used to join and support polycarbonate sheets while allowing the sheets to expand and contract naturally with temperature changes.

They also help create a weather-resistant connection between sheets and provide a neat finished appearance.

H sections are used to join polycarbonate sheets together along their length.

They are commonly used where a single sheet is not long enough to cover the full roof slope and two sheets need to be connected together.

Sealing tapes help protect the internal flutes of multiwall polycarbonate sheets.

Foil tape is normally fitted to the top edge to prevent contamination entering the sheet, while breather tape is used at the lower edge to allow condensation to escape.

Fixing buttons are commonly used to secure sheets to supporting structures and provide a neat, weather-resistant fixing point.

They should be installed correctly to hold the sheets securely while still allowing for normal thermal movement.

Flashings help create a weather-resistant seal where the roof meets walls, edges or other structures.

Correctly fitted flashings help prevent water entering around the perimeter of the roof and provide a professional finished appearance.

We recommend carrying out regular visual checks at least once or twice a year.

Spring and autumn are ideal times to inspect your roof, allowing you to identify any issues caused by winter weather and prepare the roof for heavier rainfall.

Polycarbonate sheets should be cleaned using clean water, a mild detergent and a soft cloth or sponge.

Avoid abrasive materials, harsh chemicals and pressure washers, as these can damage the surface of the sheets and reduce their lifespan.

Some condensation inside multiwall polycarbonate sheets can be completely normal.

The sheets are designed with internal air chambers, and moisture can naturally form when warm air meets colder surfaces.

Excessive condensation, dirt or insects inside the sheet flutes may indicate an issue with sealing tapes, end closures or drainage.

The best way to maximise the lifespan of your roof is to use the correct installation methods, inspect the system regularly and replace damaged components when required.

Keeping sheets clean, ensuring drainage remains clear and checking fixings and seals will help maintain long-term performance.

Signs that your roof may need attention include leaks, damaged sheets, loose components, blocked drainage, excessive condensation or visible movement within the roofing system.

Identifying problems early can help prevent more extensive repairs later.

Yes. Many problems can be resolved by replacing individual components rather than the complete roof.

Depending on the issue, this may include replacing sheets, fixings, sealing tapes, flashings or other accessories.

A leaking polycarbonate roof is not always caused by the sheet itself. Water can enter through several areas including flashings, glazing bars, fixings, sealing tapes or drainage points.

The best approach is to inspect the complete roofing system to identify the actual cause before replacing components.

Small amounts of condensation inside multiwall sheets can be normal, but visible water, dirt or insects inside the flutes may indicate an issue with the sealing system.

Check the foil tape, breather tape, end closures and drainage paths to ensure moisture can escape correctly.

Polycarbonate naturally expands and contracts as temperatures change. Some movement is expected as part of normal operation.

Excessive movement may indicate incorrect installation, insufficient allowance for expansion or issues with glazing bars and fixings.

Discolouration can be caused by dirt, algae, incorrect cleaning methods, ageing or damage to the sheet surface.

Cleaning the sheets correctly should always be the first step before considering replacement.

Polycarbonate sheets should be considered for replacement when they have significant cracks, damaged edges, loss of performance or problems that cannot be corrected through maintenance.

In many cases, replacing an individual sheet or component can restore the roof without requiring a complete replacement.

Start by inspecting the most common problem areas:

• Glazing bars and seals
• Fixing buttons
• Flashings
• Sealing tapes
• Sheet condition
• Gutters and drainage

Identifying the cause first will help avoid unnecessary repairs or replacement of components that are still working correctly.