Short answer: clean a conservatory roof from the ground or a stable stepladder, never from the roof itself. Use a soft brush or sponge on an extendable pole, lukewarm water and a mild detergent. Avoid abrasive pads, solvents and strong alkaline cleaners, particularly on polycarbonate, and don't blast seals or sheets with a pressure washer. Clear the gutters at the same time. If algae or dirt is inside the flutes of polycarbonate sheets, cleaning the surface won't shift it.
Safety first: never climb on the roof
Conservatory roof panels and glazing bars aren't designed to take a person's weight. Kneeling or leaning on them can crack panels, and falls through or from conservatory roofs cause serious injuries. Work from the ground with a pole. For the parts you can't reach safely, use a professional with proper access equipment. Don't lean a ladder against the conservatory frame or gutter either, because that can damage them.
Pick your day: clean on a mild, dry, still day. Wind makes poles hard to control, and cleaning in strong direct sun can dry soap onto the surface before you rinse it off. Some polycarbonate manufacturers specifically advise against applying cleaners in direct sunlight.
What you'll need
- An extendable pole with a soft-bristled brush or sponge head
- A bucket of lukewarm water with a little mild washing-up liquid
- A hose, or a second bucket of clean water, for rinsing
- Soft cotton or microfibre cloths for anything within reach
- Gloves and eye protection, because dirty water runs down the pole
Step by step
- Remove loose debris. Gently brush or hose off leaves and twigs first. Dragging grit across the surface is what causes scratches.
- Wet the roof. A rinse with lukewarm or cold water softens dirt and bird droppings.
- Wash gently. Work in sections with soapy water and light pressure, following the direction of the glazing bars.
- Rinse thoroughly. Rinse off all detergent with clean water so it doesn't leave a film.
- Do the inside. Clean the inside of the roof the same way, with less water. Move furniture and blinds out of the way first.
Cleaners and tools to avoid
- Abrasives. Scouring pads, wire wool and gritty powders scratch both glass and polycarbonate.
- Solvents and strong chemicals. Polycarbonate manufacturers warn against solvents, petrol-based products and high-alkaline cleaners, which can damage the sheet or its protective coating. If in doubt, test a product on a hidden corner or check the sheet manufacturer's guidance.
- Squeegees and sharp tools on polycarbonate. Some manufacturers advise against squeegees and blades on polycarbonate, because trapped grit can scratch it. Squeegees are fine on glass.
- Bleach on glass roofs. Bleach can damage coatings and seals, and it isn't needed for routine cleaning.
Should you use a pressure washer?
It's best not to. A high-pressure jet can force water past gaskets and top caps and into the frame, cause leaks, and loosen seals that were otherwise sound. Polycarbonate manufacturer guidance warns that a jet held close to a sheet can damage or even tear it. If you do use one, keep it on a low setting with a wide fan nozzle, stand well back and never aim at the seals, joints or flashing. For most roofs, a hose and a soft brush do the job.
Polycarbonate vs glass roofs
Polycarbonate
Polycarbonate is softer than glass and scratches more easily, so gentle tools and mild soap matter most here. Multiwall sheets have hollow channels, called flutes, running down their length. On a well-fitted roof the ends are sealed with tape and end closures to keep dirt and insects out. Cleaning the outside surface won't reach inside the flutes.
Glass
Glass is more forgiving. Warm soapy water works well, and you can use a squeegee from the top down to avoid streaks. Many people clean a glass roof once or twice a year, more often under trees.
Self-cleaning glass
Self-cleaning glass has a coating on the outer pane that uses daylight to break down organic dirt. It also makes rain spread out as a sheet instead of forming droplets, which helps wash the loosened dirt away. It still benefits from a rinse with clean water during long dry spells, and from a gentle clean if dirt builds up. Avoid abrasives and harsh chemicals that could damage the coating, and check the glass manufacturer's care advice before using any cleaning product on it.
Don't forget the gutters
Conservatory gutters collect leaves, moss and silt from the conservatory roof and the house roof above. When they block, water can overflow back into the frame and look like a roof leak. Clear them from a stable position on the ground or a stepladder that isn't resting on the conservatory, and check the outlet and downpipe run freely. If a gutter sags, leaks at the joints or keeps overflowing, see our page on conservatory guttering repair.
When dirty flutes mean it's time for new panels
Green or black streaks running down inside polycarbonate sheets usually mean moisture, algae or insects have got into the flutes, often because the end tape or closures have failed. This dirt is sealed inside the sheet and can't be reached by cleaning the outside. Trying to flush it out isn't reliable and can make things worse. Once flutes are badly stained, or the sheets have yellowed and turned brittle with age, the practical fix is usually replacing the affected panels. If most of the roof is affected, a conservatory roof replacement may make more sense. Moss and dirt sitting on failing seals can also be a sign that a conservatory roof seal repair is due.
When to call a professional
If you can't reach the whole roof safely from the ground, if cleaning shows up cracks, slipped sheets or perished seals, or if water is getting in, it's time for a professional. Cleaning is often a good moment to spot problems early. If you're in Liverpool, a call to our local conservatory roof repair service is an easy way to be put in touch with an independent roofer who can take a look. You can also read more about conservatory roof repairs near you on our homepage.
Frequently asked questions
Can I use a pressure washer on my conservatory roof?
It isn't recommended. A high-pressure jet can force water past seals and gaskets, cause leaks, and damage polycarbonate sheets. A hose and a soft brush on an extendable pole are safer for most roofs.
What is the best thing to clean a polycarbonate conservatory roof with?
Lukewarm water with a mild detergent such as washing-up liquid, applied with a soft brush, sponge or cloth, then rinsed off. Avoid abrasives, solvents and strong alkaline cleaners.
How do I get the green out of my polycarbonate roof?
Green on the surface can usually be washed off gently. Green inside the flutes is sealed within the sheet and generally can't be cleaned out, so badly affected sheets are normally replaced.
Does self-cleaning glass ever need cleaning?
Occasionally. The coating works best with daylight and rain, so a rinse with clean water helps during long dry spells. Heavier dirt may need a gentle clean with products suitable for coated glass.
How often should a conservatory roof be cleaned?
Many homeowners clean it once or twice a year and clear the gutters after autumn leaf fall. Roofs under trees or near busy roads may need it more often.
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