How to clean a conservatory roof

Inspired by a helpful YouTube guide. We based this walk-through on PK Window Cleaning's "Clear as Crystal Conservatory Roof Clean", which shows a professional approach to shifting algae and green deposits from polycarbonate panels. The technique works equally well on glass roofs with a few minor adjustments.

1. Check the roof condition before you start

Walk around the outside and look at the roof from a distance first. Check for cracked or discoloured panels, damaged ridge cappings, and any joints where sealant has shrunk away. Cleaning a roof that needs repairs first can drive water into gaps and make things worse.

Also check the gutters are in place and attached. Gutters that have dropped away from the fascia will channel water behind the conservatory frame rather than into the downpipe.

2. Gather the right equipment

For most conservatory roofs you will need: a soft-bristle brush or wash head on a telescopic pole, a specialist conservatory roof cleaner (not a pressure washer at full blast — more on that below), a garden hose with a spray head, and eye protection.

A telescopic pole with a brush head lets you clean safely from the ground or from a scaffold tower, without stepping on the panels. Conservatory roofs are not designed to be walked on, and polycarbonate in particular can crack or bow under weight.

3. Wet the roof and apply the cleaner

Rinse the whole roof with clean water first to loosen surface debris and any loose algae. Then apply a purpose-made conservatory roof cleaner diluted according to the instructions — most are sprayed on and left to dwell for a few minutes to break down the green growth.

Avoid household bleach directly on polycarbonate. It can cause hazing and degradation over time. Glass roofs are more tolerant, but a proper conservatory cleaner is still a better choice than kitchen bleach.

4. Scrub gently with the brush head

Work from the ridge downwards in overlapping strokes. Do not press hard — you are agitating the cleaner and loosening the algae, not scrubbing tiles. Polycarbonate scratches more easily than glass, so a soft brush is essential.

Pay extra attention to the joints around the glazing bars and ridge, where algae builds up thickest. That is where moisture sits longest and where the green staining tends to be most stubborn.

5. Rinse thoroughly from top to bottom

Once you have worked over the whole roof, rinse from the ridge down with clean water. Let the runoff carry the cleaner and the loosened algae down into the gutters. You may need to go over particularly bad patches a second time.

A low-pressure hose is fine. A pressure washer on a high setting can force water past the glazing bar seals and into the building. If you do use one, keep it on its lowest setting and hold the lance at an angle, not directly at any joint.

6. Clean the gutters while you are at it

Once the roof is clean, the gutters will have collected all the loosened debris. Clear them out with a gloved hand or a small scoop and flush them through with a hose. A blocked gutter on a conservatory will overflow behind the wall head and eventually cause damp issues indoors.

Check the downpipe is running freely too. A small ball of compacted leaves at the top of a downpipe blocks the whole run.

7. Apply an algae inhibitor

Once the roof is clean and dry, apply a biocide treatment or algae inhibitor to slow the regrowth. These are typically sprayed on and left — no rinsing needed. In a shaded or north-facing position, a treated roof can stay noticeably cleaner for a year or more.

That said, nothing stops algae permanently in the UK climate. An annual clean plus an inhibitor treatment is a realistic maintenance cycle for most conservatories.

When to call a handyman

Call Richard if the roof needs more than cleaning — if panels are cracked, sealant needs replacing, or gutters have come away from the frame. Cleaning is the easy part. Structural work or working at any real height is where a professional makes sense.