Polycarbonate roofing sheets are popular for pergolas, lean-to roofs, verandas, carports and garden structures because they are strong, lightweight and allow plenty of natural light through. Like any outdoor surface, however, they can accumulate dirt, algae, leaves and environmental debris over time.

Cleaning polycarbonate sheets properly helps maintain their clarity, extend their lifespan and keep your outdoor structure looking its best. The key is using the correct cleaning method so you don’t damage the protective UV layer or the surface of the sheet.

In this guide, we explain the safest way to clean polycarbonate roofing sheets, the tools you should use, and the common mistakes to avoid.

Helpful resources mentioned in this guide:

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

Cut-to-size multiwall 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 Cleaning Polycarbonate Sheets Matters

Over time, outdoor roofs collect dust, pollen, leaves and algae. If these contaminants are left to build up, they can reduce light transmission and affect the overall appearance of the structure.

Regular cleaning helps to:

• Maintain clear light transmission
• Prevent algae or moss build-up
• Protect the UV coating on the sheet
• Extend the lifespan of the roofing system
• Keep gutters and drainage areas clear

Fortunately, polycarbonate roofing sheets are very easy to maintain when cleaned correctly.

How Often Should Polycarbonate Roofs Be Cleaned?

Most polycarbonate roofs benefit from cleaning twice per year.

A typical maintenance schedule might include:

Spring cleaning
Remove winter debris and dirt accumulation.

Autumn cleaning
Clear leaves and organic material before winter weather arrives.

Roofs located near trees may need more frequent cleaning to prevent leaf build-up.

What You Need to Clean Polycarbonate Roofing

Before starting, gather the following materials:

• Warm water
• Mild washing-up liquid
• Soft sponge or microfibre cloth
• Soft brush or extendable brush
• Garden hose

Avoid using abrasive tools or harsh chemicals, as these can scratch the surface of the sheets.

If you need replacement accessories while maintaining your roof, you can find them here:

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

Step-by-Step Guide to Cleaning Polycarbonate Sheets

Step 1 – Remove Loose Debris

Start by removing leaves, twigs and loose dirt from the roof surface.

This can usually be done using:

• A soft brush
• A leaf blower
• Gentle rinsing with a hose

Removing loose debris first prevents scratching the surface during washing.

Step 2 – Prepare a Gentle Cleaning Solution

Mix a small amount of mild washing-up liquid with warm water.

This solution helps break down dirt, pollen and organic residue without damaging the sheet surface.

Avoid strong chemicals such as:

• Solvents
• Bleach
• Abrasive cleaners

These can damage the UV protective layer on the sheet.

Step 3 – Wash the Sheets Gently

Use a soft sponge or cloth to clean the sheets with the warm soapy water.

Work gradually across the roof surface, gently removing dirt and residue.

Always wash along the direction of the sheets, not across them, to reduce the risk of scratching.

Avoid applying excessive pressure while cleaning.

Step 4 – Rinse With Clean Water

Once the sheets have been cleaned, rinse the roof thoroughly using a garden hose.

Rinsing removes any remaining soap residue and helps restore the sheet’s clarity.

Ensure water flows downwards and into the gutter system.

Step 5 – Check Roof Accessories

While cleaning the roof, it’s a good opportunity to inspect the roofing accessories.

Look for signs of wear such as:

• Damaged glazing bars
• Loose fixings
• Worn breather tape
• Missing end caps

Replacement accessories can be found here:

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

If glazing bar end caps are missing or damaged, replacements are available here:

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

Cleaning Algae or Moss From Polycarbonate

Roofs located in shaded or damp environments may develop algae or moss over time.

To remove algae:

1. Use warm soapy water and a soft brush

2. Gently scrub the affected area

3. Rinse thoroughly with clean water

Avoid harsh algae removers or pressure washing, as these can damage the sheet surface.

Maintaining good drainage and regular cleaning helps prevent algae growth.

Can You Use a Pressure Washer on Polycarbonate?

Pressure washers are not recommended for polycarbonate roofing.

High-pressure water can:

• Damage sealing tapes
• Force water into multiwall chambers
• Lift trims or flashing
• Damage sheet surfaces

If a pressure washer must be used, it should be on the lowest setting and directed carefully.

However, a simple hose and sponge are usually sufficient for cleaning.

Avoid These Common Cleaning Mistakes

Many cleaning issues occur because of incorrect tools or chemicals.

Avoid the following:

Using abrasive sponges
These can scratch the sheet surface.

Using solvent-based cleaners
These can damage the polycarbonate material.

Using harsh chemicals
Bleach or industrial cleaners can degrade the protective coating.

Pressure washing the sheet edges
This can force water into the multiwall chambers.

Walking directly on the sheets
Polycarbonate sheets are strong but should not be used as walking surfaces.

What If Polycarbonate Sheets Become Cloudy?

If polycarbonate sheets become cloudy, it may be caused by:

• Dirt build-up
• Internal condensation
• Water inside the multiwall chambers

Cleaning often restores clarity if the issue is surface dirt.

If moisture has entered the chambers, replacement sheets may be required.

Replacement sheets can be ordered here:

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

Preventing Future Dirt Build-Up

To reduce cleaning frequency, consider these preventative steps:

• Keep nearby trees trimmed
• Clear gutters regularly
• Remove leaves before they decompose
• Rinse the roof occasionally with a hose

These simple maintenance steps help keep your roof clean and clear year-round.

Maintaining the Entire Roofing System

Cleaning the sheets is only part of roof maintenance.

You should also check:

• Glazing bars
• Flashing
• Fixings
• Sealing tape
• End closures

Proper maintenance ensures the roof remains watertight and structurally sound.

Accessories for maintenance and repairs can be found here:

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

Ordering Replacement Sheets

If a sheet becomes damaged or worn over time, replacing it is straightforward.

Many homeowners choose cut-to-size polycarbonate sheets to simplify installation and reduce waste.

Order cut-to-size sheets 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 roofing sheets are easy to maintain when cleaned properly. Using warm soapy water, a soft cloth and gentle rinsing will keep your roof clear, bright and looking its best.

Regular cleaning prevents debris build-up, protects the UV coating and ensures your roofing system performs well for many years.

With simple maintenance twice a year, a polycarbonate roof can continue providing light, protection and durability for decades.