Cleaning a roof lantern: how to do it and what to maintain

Cleaning a roof lantern is best done twice a year, in spring and after the leaves have fallen, with lukewarm water, a mild soap and a soft sponge or brush. At the same time you check the drainage, the gaskets and the sealant joints. It takes an hour or two and prevents most leaks and dirty edges. Never walk on the glass: work from a ladder, scaffold or the adjacent roof.

Why a roof lantern gets dirtier than a window

A roof lantern lies at a gentle slope, so rain washes dirt away less well than on a vertical window. Dust, pollen, leaves and bird droppings stay put, especially on the low side and along the bottom rails. The standard pitch of 8° makes sure water and dirt run off easily, see the right pitch. Under trees and along busy roads it happens faster.

Cleaning a roof lantern: the outside

Clean the outside on a cloudy, dry day. In full sun the water dries too quickly and leaves streaks. Rinse off loose dirt and sand first, so you do not rub it across the glass.

A pressure washer may seem handy, but a hard jet can force water past gaskets and joints and damage sealant. Use a garden hose with a gentle spray and a telescopic brush instead.

• Lukewarm water with a splash of pH-neutral soap
• Soft sponge, microfibre or telescopic brush with soft bristles
• Rinse with clean water, preferably demineralised
• No scouring agents, steel wool or aggressive cleaners

Inside and profiles

Inside, a damp cloth with a little soap and a dry microfibre cloth are enough. The aluminium profiles have a finish in a RAL colour; clean them with water and mild soap, without solvents that can dull the finish. On dark colours such as jet black and anthracite, limescale and fingerprints show sooner, see choosing a frame colour.

If you have frosted glass, follow the cleaning advice for that glass type and use only a soft cloth. More about this glass type in frosted glass in a roof lantern.

Yearly maintenance: drainage, gaskets and sealant

Maintaining a roof lantern is all about water: it has to be able to drain away and must not get in anywhere. A gable roof lantern has a self-cleaning drainage system in the bottom rails, but you have to keep the gutter the water runs into clear yourself. On a hipped lantern the drainage is hidden in the bars and corner profiles; check that the outlets are clear. Also check that no leaves or dirt on the bottom rails are holding the water back.

If you see a crack, a loose joint or water in the same spot, do not wait. Read what to do if your roof lantern leaks.

• Gutters, bottom rails and downpipe clear of leaves and dirt
• Check gaskets for cracks or loosening
• Inspect sealant joints for shrinkage and loose edges
• Look at the roof covering connection to the upstand

Green growth and limescale

Green growth is algae or moss that grows where things stay damp for a long time, often on the north side or under trees. Remove it with soapy water and a soft brush. An algae cleaner can help, provided it is suitable for glass and aluminium; rinse well afterwards.

Limescale marks form when hard tap water dries. Rinsing with demineralised water prevents them. If you have a screen on your roof lantern, also clean the fabric and the guides following the supplier's advice.

Frequently asked questions