Yes, though less often than a flat pane, because sloping faces shed rain and much of the dirt with it. What genuinely needs attention is not the glass so much as the drainage at the eaves, the frame finish near the coast, and the flat roof around the kerb. Those three do more for a lantern than washing the panes does.
How often the glass wants doing
Once or twice a year in most positions.
The pitched faces keep themselves reasonably clear, and what accumulates is generally along the bars and in the corners where the water does not run.
A lantern under a tree wants it more often.
Self cleaning glass
Worth specifying on something this awkward to reach.
A coated outer pane breaks deposits down in daylight and lets rain carry them away, and on a pitched lantern face that works well because the water actually flows.
How it works is on what is self cleaning glass.
Why it does not remove the job
It reduces it. A coating deals with organic deposits and general grime. It does not deal with bird mess, tree sap or salt, and it works less well where a face is sheltered from rain.
The weep holes
The maintenance that actually matters. Drainage channels in the bars discharge through small holes at the eaves, and when those silt up with dust, moss and leaf litter the channels back up.
Why that matters is on do roof lanterns leak.
How to clear them
A soft brush and a look, once a year.
They are along the bottom edge of the frame where it meets the kerb, and clearing them is a couple of minutes if it is done before they are fully blocked.
The flat roof around it
Cleaned at the same time and for the same reason.
Leaf litter and moss on the roof around a kerb dam water against the upstand, and standing water against a kerb is what eventually finds a weakness.
The outlets on the roof
The other thing to look at while you are up there.
A blocked rainwater outlet turns a flat roof into a shallow pond, and the lantern kerb is the tallest thing standing in it.
Why the fall matters is on what is the minimum fall for a flat roof with a rooflight.
Salt on a coastal site
A real consideration across our area. Salt dulls glass and works on a powder coated finish, and rinsing a lantern with plain water a few times a year does more for it than polishing does.
What exposure does is on marine grade coatings on a coastal lantern.
The frame finish generally
Wiped rather than treated. A powder coated aluminium frame needs nothing but washing, and abrasives or solvents will damage a finish that would otherwise last decades.
Reaching it safely
The part that decides how it actually gets done.
A lantern on a single storey extension is often reachable from a ladder to the flat roof, and whether the roof can be walked on is the question to answer before anybody stands on it.
Whether the roof can be walked on
Depends entirely on the build up.
A well built warm deck roof will take foot traffic. An older cold deck with thin insulation may not, and a rooflight is not a stepping point under any circumstances.
Reaching the ridge
The genuine difficulty on a large lantern.
The upper faces near the ridge are beyond arm’s reach from the roof surface, and on a big lantern that is a pole system or a professional with proper access.
Pole systems
What most people end up using.
A fed pole with a soft brush reaches the upper faces from the flat roof or from the ground, and it is how window cleaners do it.
Cleaning the inside
Harder than the outside, and needed less.
The internal faces stay clean far longer, and reaching them means working at height inside the room over whatever is beneath the lantern.
It is worth planning the room so that is possible.
What to use
Water, and very little in it.
Warm water with a drop of detergent and a soft cloth or brush handles everything, and a rinse with clean water stops it drying marked.
What to avoid
Scrapers, abrasives and pressure washers.
A blade will mark a coated pane, an abrasive will dull it, and a pressure washer aimed at a gasket will drive water past a seal that was doing its job.
Bird mess
Dealt with promptly rather than left.
It is acidic and it will etch a coating given a season, so it is worth a specific visit rather than waiting for the annual clean.
What a service visit covers
More than glass.
Weeps cleared, seals checked, fixings looked at, the covering around the kerb inspected, and any opening pane run through its stroke.
Moss on the north face
The face that stays green, and it is worth knowing why.
A north facing lantern face gets little direct sun and stays damp longer, so algae and moss establish there first, on the glass and along the bars.
It washes off and it comes back, which is normal rather than a fault.
Cleaning an opening pane
Easier than the fixed ones. An opening light can be run open and its outer face reached from inside on some arrangements, and the gaskets around it are worth wiping while it is open.
What we clear
We clear the weeps and check the covering around the kerb whenever we are back at a lantern, because those two are what keep it dry and neither is anybody’s idea of cleaning.
The whole picture is on the roof lantern installation page.
Thinking about this job? We survey across Worthing, West Sussex and the South Downs and give you a fixed price before any work starts, with a 10-year workmanship guarantee.