The short answer
A conservatory roof is cleaned from outside with a soft brush or water-fed pole and a mild, non-abrasive cleaner, reached by standing on the lawn, a tower or a platform, and never by walking on the glazing. Glass and polycarbonate both mark easily, so high-pressure jets, harsh chemicals and stiff brushes are avoided. Heavy green growth, and the gutters and seals beneath it, need the most attention.
Why nobody should walk on a conservatory roof
Glass cracks under a point load and polycarbonate flexes, sometimes enough to pop out of its glazing bars. Both can look sound from the garden and still fail under a knee or a boot. A fall through a conservatory roof is a serious injury, and the repair is far more expensive than the clean.
For that reason the job is planned around reach, not footing. A water-fed pole with a soft brush head can clear most roofs from the ground. Where the roof is too deep or the pitch too awkward, a low tower or a properly boarded platform puts the cleaner beside the glazing instead of on it. Our guide to access for roof cleaning sets out how each option works and what it does to the price.
If you have been told a conservatory roof can simply be "walked over with crawl boards", ask who is taking responsibility for that. We do not put weight on glazing.
Glass and polycarbonate need different treatment
Glass is hard but still shows swirl marks if grit is dragged across it. A soft brush, plenty of clean water and a gentle detergent are enough for most staining. Rinsing well matters, because dried cleaner leaves streaks that show up in low sun.
Polycarbonate is softer. Its surface can be scratched by abrasive pads, and some solvents cloud it or weaken it over time. Pressure washing is a particular risk, because a jet can force water into the hollow channels inside multiwall sheets, where it can sit and grow algae from within. Once that happens, the sheet will not look clean from outside however carefully it is washed.
Frames, seals and gaskets
Dirt gathers along the glazing bars, in the gaskets and in the cills. A soft brush gets in there without lifting seals. If a gasket is perished or a cap has lifted, cleaning will expose it, and it is better found than hidden.
Green growth, moss and what collects in the gutters
Conservatory roofs gather a green film, particularly along the lower edge and on any panel shaded by a tree or a neighbouring wall. Moss follows in the corners where the glazing meets the house, and in the valley gutter if there is one. Left to build, it holds water against the seals, and the weight of wet moss and leaf litter adds load to a frame built with much lighter loads in mind.
Clearing the gutters comes first, because standing water carries growth back onto the glass. Along the abutment against the house, the flashing or lead strip should be checked for gaps at the same visit. You will often find a loose edge long before any water comes into the room.
The lessons from tile roofs carry over only in part. How moss builds up and holds water is described in our answer on moss lifting roof tiles, but glazing responds to very different cleaning methods, so the two jobs are kept apart.
What conservatory roof cleaning typically costs
Cleaning a conservatory roof by itself does not have a published price that we can cite, so the figures here are only a guide to the wider market. MyBuilder's 2026 roof cleaning guide puts whole-roof cleaning at from about £300, with flat roofs at £300 to £600 and soft washing at about £15 to £20 per m². A small conservatory is a small area, but access is usually the larger part of the price, because a tower or a boarded platform costs more to set up than the cleaning itself.
Your own figure comes after we have seen the roof, and it covers the washing, the access and any repair. If the structure needs work, we discuss that with you first and never add it without your agreement.
If the roof is clad in a hard, flat material rather than glass, see our answer on cleaning a flat roof, which deals with membranes instead.
When cleaning will not be enough
Cleaning improves a conservatory roof that is basically sound. It cannot fix glazing that has aged. The Eco Experts put the typical life of a glass or polycarbonate conservatory roof at about 10 to 15 years, and HomeBuilding gives around 10 years for polycarbonate. Panels that are yellowed, crazed, cloudy inside the channels or leaking at the seals are usually past a clean.
Replacement is a bigger decision. MyBuilder's 2026 conservatory roof guide puts polycarbonate at £2,000 to £5,000, glass at £3,000 to £8,000 and a solid roof at £5,000 to £10,000, with structural reinforcement at £500 to £2,000. According to Homebuilding and Renovating, fitting a solid roof is material alteration work, so a Building Regulations application is needed, and the old frame may not carry the heavier covering without strengthening.
A swap from polycarbonate to a solid roof is therefore a survey, a structural check and an application, not a weekend job. Where the work is notifiable, we explain the consent and deal with the notification ourselves.
Deciding between a clean and a new roof
A useful test is to look inside on a bright day. If the staining is on the outside surface, a clean will transform the roof. If it is between the layers, inside the channels or beneath the seals, cleaning will only change the part you can reach.
Ask what the panels are made of, how old they are and whether any leaks have shown at the ridge or the wall junction. Photographs of those places are the most helpful thing you can send us before a visit.
Our wider guide to roof cleaning and moss removal in Stroud covers the other coverings we clean. For a conservatory, send a few pictures by WhatsApp or ring 01453 933613, and our written 10-year workmanship guarantee applies to any repair or replacement work we carry out.