How Do You Clean a Conservatory Roof?

A conservatory roof is built to keep rain out, not to carry a person. Twin-wall polycarbonate sheets are light and hollow, and a boot can go straight through them. Glass is stronger in a pane but is held in thin glazing bars that can crack or pop loose under a knee. A fall through either is a fall from height onto a hard floor, and it is how many cleaning jobs turn into emergency calls.

So the first rule is that nobody kneels, crawls or walks on the glazing. Weight goes on something that spreads it: a purpose-built roof ladder hooked over the ridge of the house roof, a tower beside the conservatory, or a long-reach brush used from the ground and the house wall. Which one suits depends on the height of the eaves, how far the roof slopes, and whether the house wall next to it is a tiled roof or a flat one.

If you cannot reach the whole surface from a safe place, that is the sign to ask a roofer. We set the access up first and decide the method afterwards, never the other way round. A tower or scaffold beside the conservatory also gives a stable place to stand for the gutter and the junction with the house wall.

Both surfaces clean best with warm water, a mild non-abrasive cleaner and a soft brush or mop on a pole. Work from the ridge down so dirty water runs off the panel you have already done, and rinse well so no film is left to dry in streaks. Moss and algae that have grown in the gaps beside the glazing bars come out with a plastic scraper or a soft brush, working along the bar rather than across it.

High-pressure jets are the usual way a roof is harmed. Water forced under the rubber or silicone seals can leak into the room, and a hard jet or a stiff brush will scratch polycarbonate, which stays scratched for good. Bleach and solvent cleaners can cloud the plastic, so use only products the sheet or window maker allows.

On the tiled or felt roof next to the conservatory, any moss treatment is applied with care so the run-off does not wash straight onto the glazing. Our page on roof soft washing explains the gentler method we prefer for tiles.

Dirt on the outside is not always the whole story. Green growth between the two skins of a polycarbonate sheet means the end seals have failed, and no amount of washing from outside will clear it. The sheet then needs resealing or replacing. Cloudy, yellowed or brittle panels have usually reached the end of their life; published guides give a typical polycarbonate roof about 10 to 15 years, but it is a range, not a promise.

Look inside as well. Stains on the ceiling plates, drips at the glazing bars, or daylight where the sheets meet the house wall point to flashing or seals that have worn, and those are repairs rather than cleaning. A cracked pane or a loose cap strip should be dealt with before any water goes near it.

We check these things on the survey and photograph them, so you can see why a clean alone would not hold. If the roof is sound, a clean is all it needs. If it is not, the written price covers the repair we find, as one total.

Most of the dirt on a conservatory roof comes from what lands on it. Overhanging branches drop leaves, sap and bird mess, and the shade they cast keeps the surface damp enough for algae and moss to settle. Trimming the branches back is often worth more than any amount of scrubbing.

Keep the gutter that serves the conservatory clear, because a blocked gutter overflows onto the glazing and leaves a tide mark. A quick look from an upstairs window each spring and autumn will show whether growth is starting. Catching it early means a gentle brush is enough, rather than scraping out established moss.

Avoid leaning ladders directly on the glass or sheets, and never pin a ladder against the glazing bars. A standoff that rests on the wall frame spreads the load safely. For a full picture of what roof cleaning costs on a house roof, see roof cleaning cost, and our roof cleaning and moss removal page covers the rest of the house. Send us a photo of the conservatory and the wall beside it, and we will say how we would reach it.