01Kit
What you need before you start
Warm water, a soft cloth and a bit of patience will do most of the job. The wrong tool does more harm than the dirt.
A roof lantern is a glazed rooflight raised above a flat roof, so it collects the same grime as any skylight: rain streaks, pollen, bird droppings, leaf mush and the green film that settles on the shady side. In south Essex, with plenty of trees in Basildon, Billericay and Wickford gardens, the lantern gets a coat of that every season. The good news is that how to clean a roof lantern is no mystery: with the right kit and a safe way to reach it, it is an easy job.
Keep it simple. You are cleaning coated glass and a painted or anodised frame, and both scratch or dull if you scrub them with the wrong thing. The coating on modern glass, which helps keep heat in, sits on the inside faces of the sealed unit, so the outer pane is ordinary tough glass. Even so, grit dragged across it leaves fine lines you will see every time the sun hits.
- A bucket of lukewarm water with a small squeeze of washing-up liquid
- A soft sponge or microfibre cloth, and a second clean cloth to dry
- A long-handled soft brush or a water-fed pole, for the ridge and the far side
- A squeegee with a clean rubber blade for the glass
- A garden hose to rinse, ideally with a gentle spray head
- A stable step ladder, or a platform you can stand on safely
Leave the pressure washer in the shed. A hard jet can push water past the glazing seals and strip the paint off a frame. A garden hose is plenty.
02Method
Cleaning it, step by step
Work from the top down, rinse often and never let the cleaner dry on the glass.
Here is how to clean a roof lantern well. Pick a dull, dry day. Direct sun dries the suds before you wipe them, which leaves streaks you then have to do again. A cool, overcast morning is perfect, and a dry spell means you will not undo the work with the next shower.
- Clear loose leaves, moss and twigs from the roof around the base and from the gutter or gap beside the frame, by hand or with the soft brush.
- Wet the whole lantern with the hose so the surface dirt loosens and grit floats off instead of scratching.
- Wash the glass and frame with the soapy water, a section at a time, starting at the ridge and working down the slopes.
- Rinse each section straight away with clean water.
- Squeegee the glass from top to bottom, wiping the blade on a cloth between strokes.
- Dry the frame and the edges of the glass, so no water sits in the joints.
Bird mess needs a minute. Lay a soaking wet cloth over it for a few minutes to soften it, then wipe it off. Do not scrape it with a fingernail or a blade. For moss and green film on the frame, a soft brush and a mild solution of a proper outdoor cleaner made for glazing and aluminium or PVC is fine. Check the label, and rinse it off thoroughly.
Do not use bleach, abrasive pads, scouring powder or white spirit. Harsh solvents can mark the frame finish and attack the rubber seals around the glass. Our guide on aluminium versus uPVC roof lanterns explains why the two frame materials like slightly different treatment.
03Access
Reaching it without taking a risk
The glass is not a place to stand, and a flat roof is not a safe place to work alone.
Never walk on a roof lantern, and never lean your weight on the glass. Even strong glazing is not made to take a person. If the lantern sits on a single-storey extension, the safe way is usually to clean it from a ladder against the wall, using a long-handled brush to reach the ridge. A water-fed pole lets you do the whole job from the ground, which is what window cleaners use and what we would suggest for anything bigger than a small lantern.
Step ladders and flat roofs go badly together in wet or windy weather. If you cannot reach the lantern from a firm, level footing, do not stretch. Ask a window cleaner who has the poles and the insurance to do it. A few minutes of their time is cheaper than a fall.
04Upkeep
How often, and what else to look at while you are there
Twice a year keeps most lanterns clear, and every clean is a chance to spot a small problem early.
A good rhythm is spring and autumn. Spring clears winter grime and the first of the pollen. Autumn clears leaves before they rot into the frame. Lanterns under trees or close to the road may want a third wash, and a lantern in an open garden may get by with less. There is no fixed rule, so go by how it looks.
While you are up there, look rather than just wipe. A cleaning visit is the easiest way to spot trouble before it becomes expensive.
| What you see | What it may mean |
|---|---|
| Mist or droplets between the panes | The seal on that glass unit has failed and it needs replacing |
| Standing water or leaf piles at the base | The roof needs clearing so water can run away from the upstand |
| Gaps or cracked sealant at the glass edge | Worth having the fit looked at before winter |
| Flaking paint or bubbling on the frame | The coating is wearing, and it is better dealt with sooner |
If the glass inside the lantern is misted between the panes, no amount of cleaning will clear it, because the moisture is sealed inside. That unit needs replacing, and sometimes the whole lantern is due, as set out in replacing an old rooflight. The condition of the raised base also counts: our page on the roof lantern upstand explains what you should see at the foot of the glass.
Some lanterns come with a self-cleaning coating on the outer pane. It helps rain wash the glass, but it does not do the whole job, and it still wants a gentle clean a couple of times a year. For the full range, and a warm specification to go with it, see our main roof lanterns page.
Getting at the glass: cleaning a roof lantern, answered
Can I use a pressure washer on a roof lantern?
We would not. A hard jet can force water past seals and strip paint from the frame. A garden hose, warm soapy water and a soft brush are enough, and they are much kinder to the glazing.
How do I clean a roof lantern from the inside?
Use a microfibre cloth and a glass cleaner you would use on a normal window. Reach the highest panes with a long-handled mop or a telescopic pole, and keep a dust sheet underneath for drips. Take care with any blind fitted inside the glass.
Why does my lantern look dirty again a week after I cleaned it?
Usually it is the drying that went wrong. Soap or hard water left to dry on the pane shows up as streaks and spots. Rinse well and squeegee or wipe dry. Tap water in south Essex is hard, so a final wipe or a water-fed pole with purified water gives a cleaner finish.
Does the dirt on my skylight affect how warm the room is?
A little, but only through daylight and winter sun. A grimy rooflight blocks some of the light and the free warmth that comes with it, so a clean one makes the room brighter and slightly warmer. The insulation of the glass and kerb does not change.
