Question answered
Cleaning a conservatory roof
The short answer
Clean a conservatory roof with warm water, a mild non-abrasive cleaner and a soft brush on a long handle, working from the ground or the inside where you can. Avoid high-pressure jets, scourers and strong solvents, which scratch the surface and can force water past the seals. Never stand on the roof: glass and polycarbonate are fragile, and a fall through them is serious.
A conservatory roof stays clear with a soft brush, clean water and a safe way to reach it. The real risk is the roof itself, which is fragile, so how you get at it matters as much as what you use.
Getting at the roof without standing on it
The first rule is that the roof will not carry you. Polycarbonate flexes and glass can shatter, and neither warns you before it gives way. Do not lean a ladder on the sheets or kneel on the bars, even for a moment, and do not trust a roof just because it looks strong from below.
The safest methods keep both feet on the lawn. A long-handled soft brush or a water-fed pole reaches a good deal of a lean-to or Victorian-style roof from the garden. For the parts you cannot reach, a professional uses a roof ladder or crawl boards that spread the load across the bars, together with a plan for preventing a fall. Do not improvise that at height. If the roof sits under a first-floor window or has the house wall rising behind it, ask for help instead.
What to use and what to leave in the shed
Warm water with a little washing-up liquid, or a cleaner made for glazing, is enough for ordinary dirt. Work from the ridge down so the run-off carries the loosened grime away, and rinse well so residue does not dry into streaks. A microfibre cloth or a soft sponge keeps the surface from scratching, and a squeegee on a pole finishes glass neatly. Rinse the sponge often, because grit trapped in it is what scratches.
Leave out the pressure washer, the wire brush, the scouring pad and the bleach. A jet can drive water behind the cappings and into the glazing channel, where it turns up later as a drip. Polycarbonate scratches easily, and strong solvents can cloud it. Check the sheet maker's advice if you have it, and test any new cleaner on a small corner first before you commit the whole roof. A cleaner that leaves a haze on a test patch will leave one everywhere.
Moss, algae and the green line along the bars
Green growth settles where water lingers: along the bar edges, under the cappings and at the foot of the slope. On a conservatory roof the cause is usually shade from a tree or a wall, combined with a low pitch that drains slowly. Scrubbing it off without dealing with the shade only buys a few months.
Remove what you can with the soft brush and warm water, then look closely at the bar edges. Persistent growth beneath a capping can mean the seal has opened and is holding damp, and our page on conservatory bar cappings shows how to tell. Overhanging branches are worth cutting back, and the gutter at the foot of the roof should run clear so water does not sit against the sheets. Leaf litter in the valley between the conservatory and the house wall holds damp against the lower edge and feeds the same green line.
How often, and when cleaning is not enough
Cleaning a couple of times a year keeps a roof presentable, and more often under trees. Choose a dry, cloudy day, because direct sun dries the cleaner onto the surface in streaks. A roof left for years may need several passes before it comes clear, so do not judge the result from the first. Rinsing the inside face at the same time shows you which side the dirt is really on.
Cleaning can only restore a surface, not repair a failing one. Yellowed, chalky or crazed polycarbonate will not come clear, and a leak that appears after a wash belongs to the seals rather than to the water you used. Our guide to replacing individual conservatory roof panels shows when one sheet is the answer. Coated glass is worth reading about as well, in self-cleaning glass on a conservatory.
Paying someone to do it
MyBuilder gives typical UK prices for roof cleaning that start from around £300 (guide updated 21 August 2026), with higher figures for larger or harder-to-reach roofs. That is a general roof-cleaning number rather than a conservatory one, so the price on your own roof turns on its area, how it is reached and how much growth has built up. A roof with a wall behind it and no side access costs more to reach.
Ask whoever you hire how they will reach the roof, which cleaner they plan to use, and why. If the answer involves standing on the sheets or a pressure jet, look elsewhere. Our roof cleaning and moss removal service covers the house roof, and the conservatory roof replacement page explains what is involved if you decide the roof has had its day.
Conservatory roof cleaning: two quick answers
Will vinegar or bleach clear algae from polycarbonate?
Neither is a good idea. Bleach can discolour sheets and attack the rubber gaskets, and acids can mark the surface. Warm water, a mild cleaner and a soft brush are slower but safer. For the green line at the bar edges, repeat the brushing after a few dry days rather than reaching for something stronger.
Can I clean the inside of the roof as well?
Yes, and it is often easier. Use the same cloth and cleaner from a stable step platform. Water that runs down the inside on cold mornings may point to condensation or poor ventilation rather than a leak, which is worth sorting before you assume the seals have gone.
Tell us about your roof
Describe what is happening and we will call you back to arrange a visit.
- Photographs of what we find
- A written quote with one total price
- Or call 01903 299063
10-year workmanship guarantee, in writing.