Polycarbonate roof FAQs

What thickness polycarbonate sheet should I use for a pergola roof?

For most garden pergolas, 16mm multiwall polycarbonate offers the best balance of strength, light transmission and insulation.

  • 10mm works well for small canopies, lean-tos and budget-friendly designs.

  • 16mm is the most popular for pergolas and outdoor structures.

  • 25mm provides superior insulation for enclosed garden rooms or winter-use spaces.

If you’re unsure which thickness is right for you, feel free to contact our team for advice.

Do multiwall polycarbonate sheets turn yellow over time?

High-quality multiwall sheets, like our Corotherm range, include a UV-protected outer layer. This protective coating prevents yellowing, clouding, and surface degradation.

As long as the sheet is installed with the UV-treated face outward, it will retain clarity and performance for many years.

Can I cut polycarbonate roofing sheets myself?

Yes. Multiwall polycarbonate can be cut using common tools such as:

  • A circular saw with a fine-tooth blade

  • A jigsaw

  • A fine-tooth handsaw

Tips:

  • Keep the protective film on while cutting

  • Support the sheet fully to prevent vibration

  • After cutting, seal open flutes with breather tape and fit end closures to prevent moisture ingress

What pitch does a polycarbonate roof need?

A minimum pitch of 5° is recommended for multiwall polycarbonate roofing. This helps:

  • Ensure proper water run-off

  • Prevent pooling

  • Reduce the risk of leaks

  • Maintain material warranty requirements

Some glazing systems may require more than 5°, so always check the manufacturer’s installation guidelines.

How long do multiwall polycarbonate sheets last?

Multiwall polycarbonate is a durable, long-life roofing material.
With correct installation and maintenance, it can provide reliable service for many years.

Most reputable brands offer warranties covering:

  • Light transmission

  • Weather resistance

  • UV performance

  • Structural integrity

This gives a strong indication of expected lifespan.

Do polycarbonate sheets provide good insulation?

Yes. Multiwall sheets outperform single-skin plastics and traditional glass because the internal chambers trap air and reduce heat transfer.

Typical insulation levels:

  • 10mm – basic insulation

  • 16mm – ideal for pergolas and outdoor rooms

  • 25mm – high insulation, suitable for enclosed spaces

If you want warmth retention in a garden room or office, 25mm is the best choice.

Can you walk on a polycarbonate roof?

No. Polycarbonate sheets are not designed to support body weight. Walking directly on them can cause:

  • Cracking

  • Bowing

  • Damage to glazing bars

If access is required for maintenance, always use:

  • Crawl boards

  • Platforms

  • Edge protection

These spread the load safely across the supporting structure.

How is delivery handled for polycarbonate sheets?

We use specialist couriers experienced in transporting large, lightweight materials.

Delivery information:

  • Dispatched from Chesterfield, UK

  • Typical lead time: 3–5 working days

  • Delivery charge shown at checkout

  • Larger sheets may require assistance unloading upon arrival

You will receive tracking updates and estimated delivery windows once your order has been dispatched.

How do I stop condensation inside polycarbonate sheets?

Condensation is normal because the internal chambers hold air. To minimise moisture build-up:

  • Seal the top edge with aluminium foil tape

  • Seal the bottom edge with breather/vent tape

  • Fit end closures to allow moisture to escape

  • Ensure the roof has a minimum 5° pitch

  • Avoid sealing the bottom edge with solid tape (it traps moisture)

Correct ventilation is the most important factor.

Which colour polycarbonate sheet is best?

The best colour depends on the application:

  • Clear – maximum light transmission

  • Opal (white) – softer, diffused light; reduces glare

  • Bronze – reduces brightness; ideal for sunny gardens

  • Heat-reflective / solar-control – reduces heat build-up in enclosed spaces

For pergolas, clear or bronze are the most popular.

What is the maximum sheet length for polycarbonate roofing?

Multiwall polycarbonate sheets are available in lengths up to around 7 metres, depending on thickness and manufacturer.

However, for ease of installation and reduced delivery constraints, most customers choose lengths between 2m and 5m.

Do I need glazing bars for multiwall polycarbonate roofing sheets?

Yes. Sheets must always be supported and joined using:

  • H-section glazing bars or

  • Snap-fix glazing bar systems

These provide:

  • Correct support

  • Expansion allowance

  • Weatherproof seals

  • Safe fixing points

Never screw polycarbonate sheets directly through the surface without the correct system.

How do I allow for thermal expansion?

Polycarbonate expands and contracts with temperature. To prevent buckling or cracking:

  • Leave a 3–5mm expansion gap in glazing bars

  • Use fixing buttons with oversized holes

  • Never over-tighten fixings

  • Install sheets with the UV-protected face outward

Your glazing bar system will provide exact expansion guidelines.

Can polycarbonate sheets be cleaned easily?

Yes. Cleaning is simple:

  • Use warm water mixed with mild detergent

  • Use a soft sponge or cloth

  • Rinse thoroughly with clean water

  • Avoid solvents, aggressive chemicals or abrasive pads

  • Do not use high-pressure washers close to sheet edges or joints

Regular cleaning helps maintain clarity and UV protection.

Are polycarbonate sheets noisy in the wind?

Correctly installed sheets should be quiet. Noises usually come from:

  • Sheets not being fixed securely

  • Too much expansion due to tight fixings

  • Inadequate support spacing

  • Poor-quality glazing bars

Using a proper glazing bar system and following installation spacing prevents rattling.

Can I use polycarbonate sheets for a carport roof?

Yes — multiwall polycarbonate is ideal for carports because it is:

  • Lightweight

  • Strong

  • UV-resistant

  • Impact-resistant

  • Easy to install

16mm and 25mm sheets are normally recommended depending on structure size.

What accessories do I need with polycarbonate roofing?

Typical accessories include:

  • Glazing bars

  • Breather tape

  • Aluminium foil tape

  • End closures

  • Fixing buttons

  • Wall flashing tape

  • Screws & washers

Accessories ensure the roof is watertight, supported and condensation-controlled.

How long does installation take?

A standard pergola or lean-to roof using multiwall polycarbonate usually takes:

  • 2–4 hours for DIY

  • 1–2 hours for experienced installers

Larger roofs or enclosed garden rooms may take longer.

Can polycarbonate sheets be used vertically as cladding or screens?

Yes. Multiwall polycarbonate can be installed vertically:

  • As privacy screens

  • As greenhouse glazing

  • As shed windows

  • As lightweight wall panels

Just ensure edges are sealed and the UV-protected face points outward.

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