Ring round five window cleaners in North Lanarkshire and ask them to clean your conservatory roof. Most will say no. A couple won’t ring you back at all.
I’m not having a go at them — it’s an awkward job and it’s easy to do damage. But it does mean most people have no idea what’s actually meant to happen up there, which makes it very hard to tell a fair quote from a bad one.
So here’s the whole thing, start to finish.
Why it goes green in the first place
A conservatory roof is the flattest, dampest, shadiest surface on your house. It sits at a low pitch, so water sits on it rather than running off. It’s usually tucked against the back wall, so it gets less wind and less sun than the main roof.
Algae likes all three of those things.
On polycarbonate you get the green film first, then the streaks running down the flutes. The flutes are hollow, and once algae gets inside them you can see it through the panel from underneath — that dirty striping people assume is permanent staining. Usually it isn’t.
On glass you get less green and more of a dull grey film, plus the white water-spotting that comes off hard water drying in place.
And on both, the aluminium or UPVC frames pick up a black line where the seal meets the panel. That line is the bit that makes the whole roof look old.
What I actually do, in order
1. The gutter first. Your conservatory has its own gutter, and it is the single most forgotten gutter on any house. It’s low, it’s narrow, it’s usually behind a downpipe, and nobody ever looks in it. I clear it before I touch the roof, because if I clean the roof first everything I take off goes straight into it.
2. Soft wash, not pressure. Low pressure and a cleaning solution, worked with a soft brush on an extension pole. Never a pressure washer.
A pressure washer on polycarbonate will craze the surface and force water past the capping seals. On glass it’s the seals and the glazing bars that suffer. Either way you get a roof that looks great for a season and leaks the winter after. If someone offers to power-wash your conservatory roof, that is your cue to get another quote.
3. The frames and the capping bars. This is where the visible difference comes from. The panels going clear is nice; the black line disappearing off the bars is what makes people say it looks new.
4. The finials and the ridge. Small thing, takes two minutes, and it’s the bit that’s obviously been skipped when it has been.
5. Rinse with pure water. Same water I use on your windows — filtered, no minerals in it. It dries without spotting, so I don’t have to towel-dry a roof I can’t safely stand on.
6. The glass, and the windows below. If I’m already there, the conservatory windows and the patio doors get done too. It’d be daft not to.
What I won’t do
I won’t walk on it. Neither should anyone else. Polycarbonate will not take your weight and the glazing bars are not a ladder. Everything is done from the ground with poles, or off a ladder footed on solid ground at the side.
I won’t promise to remove algae from inside the flutes. Sometimes it clears, sometimes it doesn’t, and it depends on how long it’s been in there. I’ll tell you which one I think you’ve got before I start, not after you’ve paid.
I won’t guarantee a leaky roof will stop leaking. Cleaning a roof sometimes reveals a seal that was already gone. Better you know.
When to get it done
Late summer through to October is the sweet spot round here.
The reason is simple: you stop using the conservatory around then, and you start looking through the roof at a grey sky for six months. A dirty roof in July doesn’t bother anyone because nobody’s looking up. The same roof in November makes the whole room feel like a shed.
The other reason is light. A green polycarbonate roof cuts a surprising amount of daylight out of a room that only really works because of the daylight. You notice that most in winter, when there isn’t much to spare.
What it costs
From £30, and I’ll be straight with you about what that number means.
£30 is a small lean-to roof, done while I’m already at the house for the windows or the gutters. That’s the honest bottom of the range and it exists because the extra trip-out is the expensive part of any job, and there isn’t one.
A standalone conservatory clean — Victorian or Edwardian shape, full roof, frames, gutter, glass — is more than that, and I quote it after I’ve seen it. Size, pitch, access and how far gone it is all move the number.
What I won’t do is give you a price over the phone for a roof I haven’t looked at, then find a reason to put it up when I’m standing in your garden.
Worth doing if…
- You can see green or streaking from inside, looking up
- The room feels darker than it used to
- The capping bars have gone from white to grey-black
- You’re getting the gutters or the fascias done anyway — this is the cheapest it will ever be, because I’m already there
Send me a photo taken from inside looking up, plus your postcode, and I’ll tell you what it needs and what it’ll cost. If the answer is leave it another year, I’ll say that.
07440347383
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