How do you clean a roof lantern?
Twice a year, with warm water, a soft cloth or a microfibre head on a telescopic pole, working from the ridge downwards. No abrasive pads, no scouring cream, no blade. That covers the outside of nearly every domestic lantern, and on most rear extensions it can be done from the ground or from a stepladder on a firm surface.
The glass is the easy half. The part that actually earns the time is the line where the frame meets the roof, because debris collecting there is what causes trouble years later. This page covers both, and it assumes the lantern was fitted properly in the first place, which is where roof lantern installation starts.
How often, and what decides the interval
Twice a year suits most sites: once in late autumn after the leaves have come down, once in spring after the winter grime. Where a lantern sits under a mature tree, three times is more realistic, and the autumn visit becomes the important one.
Sites near arable land east of Chelmsford pick up dust at harvest, and coastal properties on the Blackwater and around Canvey get a salt film that dulls the glass faster than inland houses. The honest test is to look up from the room below on a bright day. If the sky has gone slightly milky, it is time.
Why the pitch does most of the work for you
A lantern is pitched, typically somewhere around twenty five degrees, and that angle is the reason it stays cleaner than a flush unit in the same roof. Rain runs off rather than sitting, and what runs off carries dust with it. A flat rooflight collects a rim of silt around its edge that a lantern largely sheds.
The consequence is that the lower third of each pane, nearest the eaves bar, does the most collecting. That is where run-off slows and where the tidemark forms, so that is where the cloth should spend its time.
What lands on lantern glass in this part of Essex
Four things, in roughly this order. Organic debris: leaves, blossom, seed cases and lime honeydew, which is sticky and traps everything else. Airborne dust and pollen, which forms the general haze. Bird droppings, which are acidic and want removing quickly rather than left to bake on. And moss or algae, which colonise the shaded edges rather than the open glass.
Only the last two need any real effort. The rest comes off with warm water and a little washing up liquid, which is a mild detergent and does no harm to a modern coating or a polyester powder finish.
The kit that works, and the kit that leaves marks
What works: a bucket of warm water, a soft microfibre cloth or a lambswool applicator, a telescopic pole with a squeegee head, and a second dry microfibre for a final pass. Distilled or filtered water leaves fewer spots on a sunny day than hard Essex mains water does.
What to keep away from the glass: wire wool, melamine sponges, kitchen scouring cream, bleach and any solvent-based cleaner. All of them will mark a self-cleaning coating permanently. Keep pressure washers off it entirely. The pressure will not break toughened glass, but it will drive water past a gasket that was never designed to be hit at that force.
Working order, ridge bar downwards
Wet the whole pane first and let it sit for a minute so the dirt softens. Start at the ridge and work down towards the eaves bar, so the dirty water runs onto glass you have not finished rather than glass you have. Do one pane at a time and finish it before moving on.
Then squeegee in overlapping strokes, wiping the blade between passes, and dry the frame edges and the gasket line with the second cloth. Water sitting in the corner of a gasket is where the ring marks come from. On a bright day, work on the shaded side first, because glass that dries before you have squeegeed it will spot.
Cleaning the inside face
The inside is generally easier and needed less often, since nothing lands on it except cooking film and dust. A kitchen lantern over a hob picks up a grease haze that ordinary glass cleaner shifts without difficulty.
Height is the practical problem. A lantern adds several hundred millimetres above an already high ceiling, so a stepladder rarely reaches the ridge from inside. A pole-mounted microfibre with a slightly damp head does the job from floor level, and a dry pass afterwards stops streaking. Do this on an overcast day. Low sun through the glass shows every streak and makes the work impossible to judge.
Coated glass, and the habit it reduces rather than removes
Many lanterns are ordered with a self-cleaning outer coating. It works in two stages: sunlight breaks down organic film on the surface, and rain then sheets across the pane instead of beading, carrying the loosened material off. On a pitched lantern it works noticeably better than on a flush unit, because the run-off has somewhere to go.
It does not mean never touching the glass. Bird droppings, tree sap and building dust still want washing off, and a coated pane in a sheltered spot that never gets direct rain will still film over. Treat it as halving the frequency rather than removing the job.
The gutter and the kerb line, which matter more than the glass
This is the part worth doing properly. Around the base of the lantern is a junction between the frame, the upstand and the roof covering, and leaves collect against it. Once that dam holds water, the covering is standing in it for days at a time.
Clear it by hand with a glove each autumn, then check that water leaving the lantern has a clean run to the outlet. Look at the outlet itself while you are up there. Most water problems that appear around a lantern begin as a drainage route that quietly closed itself, and five minutes in October avoids a long conversation in February.
Getting up there safely, and when not to
A single storey rear extension is usually reachable with a pole from the ground or from a stable stepladder on paving. That is the sensible limit for a homeowner. Standing on a flat roof of unknown condition, or leaning a ladder against a lantern frame, is how the glass and the person both come to grief.
Two storey work, a lantern over a side return with no safe standing, or anything requiring a foot on the covering belongs to someone with the right access equipment. Sunspire looks over the perimeter detail whenever it is on site for other work, and the ten year workmanship guarantee sits behind the detailing rather than behind the cleaning routine.
Tell us about your roof
We start with the building, the covering and the slope. Then we tell you what will suit it, and what it will cost, as a fixed written number.
- Surveyed before it is priced
- 10-year workmanship guarantee
- Building Control notification handled
- New installations and replacements