Polycarbonate roofing is a popular choice for pergolas, lean-to roofs, verandas and carports because it is lightweight, durable and allows natural light through. However, one common concern is noise during heavy rain.

If your polycarbonate roof sounds loud or echoey when it rains, don’t worry — this is a common issue and can usually be improved with a few adjustments. In this guide, we explain why polycarbonate roofs can be noisy and how to reduce or eliminate the sound.

Helpful resources mentioned throughout this guide:

Multiwall polycarbonate accessories
https://polycarbonatex.co.uk/collections/multiwall-accessories

Cut-to-size polycarbonate sheets
https://polycarbonatex.co.uk/products/cut-to-size-multiwall-polycarbonate-sheet

Glazing bar end caps
https://polycarbonatex.co.uk/collections/multiwall-accessories/products/corotherm-multiwall-polycarbonate-sheet-glazing-bar-end-cap

Delivery policy
https://polycarbonatex.co.uk/pages/delivery-policy

Why Polycarbonate Roofs Make Noise in the Rain

Polycarbonate sheets are lightweight, which means they can amplify the sound of raindrops hitting the surface.

Several factors influence how noisy a roof becomes:

• Sheet thickness
• Roof structure
• Rafter spacing
• Installation quality
• Surrounding environment

Thinner sheets and poorly supported roofs tend to produce more noise.

1. Sheet Thickness and Noise Levels

One of the biggest factors affecting noise is the thickness of the polycarbonate sheet.

Thinner sheets (4mm–6mm)

• More flexible
• Vibrate more when rain hits
• Produce louder noise

Thicker sheets (10mm–16mm+)

• More rigid
• Absorb impact better
• Reduce vibration
• Quieter during rainfall

Solution

If noise is a concern, upgrading to thicker multiwall sheets can significantly reduce sound levels.

Order cut-to-size sheets here:

https://polycarbonatex.co.uk/products/cut-to-size-multiwall-polycarbonate-sheet

2. Rafter Spacing and Structural Support

If the rafters supporting the roof are spaced too far apart, the sheets will flex more during rainfall.

This flexing increases vibration, which creates noise.

Solution

• Reduce rafter spacing if possible
• Ensure glazing bars are aligned with rafters
• Add additional support where needed

Better structural support reduces movement and helps dampen sound.

3. Glazing Bars and Fixings

Glazing bars play an important role in securing the sheets and reducing movement.

If glazing bars are:

• Loose
• Poor quality
• Incorrectly installed

…they can allow the sheets to move slightly, increasing noise levels.

Solution

• Ensure glazing bars are properly installed
• Replace worn or loose components
• Use high-quality glazing systems

Replacement accessories can be found here:

https://polycarbonatex.co.uk/collections/multiwall-accessories

If glazing bar end caps are missing or damaged, replace them here:

https://polycarbonatex.co.uk/collections/multiwall-accessories/products/corotherm-multiwall-polycarbonate-sheet-glazing-bar-end-cap

4. Roof Pitch and Water Flow

The pitch of the roof affects how rainwater interacts with the surface.

A steeper roof allows water to run off quickly, reducing the impact time of each raindrop.

A flatter roof can cause water to sit longer on the surface, increasing noise.

Solution

Ensure your roof has a pitch of at least 5°, with slightly steeper angles improving water runoff and reducing noise.

5. Insulation and Under-Roof Structures

Adding insulation or a structure beneath the roof can help absorb sound.

For example:

• Timber beams
• Fabric canopies
• Ceiling panels

These elements reduce the echo effect and make rainfall sound less intense.

6. Sheet Colour and Finish

Polycarbonate sheets are available in different finishes, which can influence how light and heat are managed.

Some finishes, such as opal or tinted sheets, can slightly reduce glare and soften the impact of rainfall noise.

While the difference is not dramatic, it can contribute to a more comfortable environment.

7. Loose Components and Vibration

Noise can sometimes come from loose components rather than the sheets themselves.

Check for:

• Loose glazing bars
• Loose fixings
• Unsecured trims
• Gaps in the roofing system

Solution

Tighten or replace any loose components to reduce vibration.

Compatible accessories are available here:

https://polycarbonatex.co.uk/collections/multiwall-accessories

8. Environmental Factors

The surrounding environment can also affect noise levels.

Factors include:

• Open areas with no sound barriers
• Large roof surfaces
• Nearby walls that reflect sound

Adding elements such as fencing, plants or structures can help absorb sound and reduce noise levels.

9. Upgrading Your Roofing System

If noise is a major concern, upgrading your roofing system can make a significant difference.

Consider:

• Switching to thicker polycarbonate sheets
• Improving rafter spacing
• Installing higher-quality glazing bars
• Adding insulation or internal structures

These improvements can transform the overall performance of the roof.

10. Maintenance to Reduce Noise

Regular maintenance helps ensure the roof performs properly and remains quiet.

Maintenance tasks include:

• Checking glazing bars and fixings
• Ensuring tapes are intact
• Cleaning the roof
• Inspecting for movement or damage

Well-maintained roofs tend to produce less noise.

When to Replace Polycarbonate Sheets

If the sheets are old, thin or damaged, replacing them may be the best solution.

Signs replacement may be needed include:

• Excessive flexing
• Visible cracks
• Persistent noise despite adjustments
• Poor overall performance

Replacement sheets can be ordered here:

https://polycarbonatex.co.uk/products/cut-to-size-multiwall-polycarbonate-sheet

Delivery information can be found here:

https://polycarbonatex.co.uk/pages/delivery-policy

Conclusion

Polycarbonate roofs can sometimes be noisy during rain, but this is usually due to sheet thickness, structural support or installation factors. By choosing thicker sheets, improving support and ensuring the roofing system is installed correctly, noise can be significantly reduced.

With the right adjustments, a polycarbonate roof can provide a comfortable, quiet outdoor space while still delivering excellent durability and natural light.