How do you look after a roof window?

A roof window is a sealed double or triple glazed unit set in a timber or polyurethane frame, hinged so the sash opens, and surrounded by a metal flashing kit that carries rain over the frame and back onto the roof covering. Each part ages at its own pace.

The glass itself rarely gives trouble. What wears first is the soft material: the rubber or foam seals that press against the sash, the paint or lacquer on a timber frame, and the lubricant in the hinges or the pivot. The flashing is metal, so it lasts well, but it depends on the tiles or slates beside it staying put. A slipped tile next to a window frame can send water into the gap long before the window shows any fault of its own.

Our page on roof window flashings explains what the kit does.

Mild detergent in warm water, applied with a soft cloth or sponge, is all it needs. Rinse with clean water and dry with a chamois or a lint-free cloth. Avoid abrasive pads, solvent cleaners and anything gritty, because the outer pane often carries a self-cleaning or low-emissivity coating that hard rubbing can mark.

The inside is simple. Open the sash, wash both faces of the inner pane and wipe the frame. A long-handled cleaner helps when the window sits high above a stair.

The outside takes more thought. Most roof windows have a sash that pivots or hinges so the outer pane can be reached from inside, and that is the safe way to do it. Do not step out onto the slope. Moss and bird droppings on the glass can be soaked off from the inside position, and anything beyond that is a job for someone with proper access equipment.

Pick two dates, say the end of autumn and the end of spring, and run through the same short list each time.

• Close the sash and look at the perimeter seal. It should sit evenly, with no gaps, splits or hard flattened stretches.
• Open and close the sash a few times. It should move smoothly and hold at each setting without being propped.
• Wipe the seals with a damp cloth and a thin smear of silicone-free lubricant if the manufacturer advises it.
• Check any trickle vent or air flap. Many roof windows have a vent slot in the top of the frame behind a filter strip, which can clog with dust, spider webs and pollen. Clean it with a soft brush or vacuum nozzle, and replace the filter if it has gone grey or brittle.

A stiff hinge or a seal that no longer meets the frame is usually cheap to put right if you catch it early. Left alone, a failed seal lets cold air whistle in, and in a bedroom that shows up as a draught long before it shows up as a stain.

Binoculars from the garden show plenty. Look at the tiles or slates beside and below the window: are any cracked, slipped or missing? Is the metal flashing still pressed down along every edge, or has a corner lifted? Is there a green line of moss or a drift of leaves piled against the frame?

Leaves are the usual culprit. They gather in the channel above the window and in the gutters formed around a roof window kit, hold water against the frame and push it sideways under the flashing. Clearing that debris is a small job for a roofer on a gutter-clear visit.

Indoors, study the angled board that links the frame to the ceiling. A brown ring, flaking paint or a patch of black mould in a corner tells you moisture is getting in or condensation is collecting. Our guides on a leaking roof window and roof window condensation help you tell the two apart.

Blinds and shutters fixed to the frame add moving parts to the same job. Check the side guides, the cords or the solar panel on a powered blind, and the fixings that hold the cassette in place. If a blind is rubbing on the sash, it will wear the paint and eventually the seal. Our page on roof window blinds covers the options.

Locks and handles deserve the same quick look. A handle that has loosened on its screws can stop the sash closing fully, and a latch that does not engage leaves a window that looks shut but is not. If you are thinking about stronger locks, read about roof window security first.

An electric or solar window adds a motor, a rain sensor and a control unit. Test the rain sensor by dabbing a damp cloth on it and watching the window close, as the manufacturer's leaflet will describe.

Everything above sits within reach of the room. The line is the roof itself. Re-seating a tile, re-dressing a lifted flashing, replacing a failed sash seal on the outside or reglazing a unit means working on the slope or from a scaffold, and that is where we come in.

If you ring or message us, tell us the make and the number printed on the label inside the sash frame, the age of the window if you know it, and where the problem shows. Photographs of the window from inside and the roof from the garden help. The survey covers the frame, the flashings and the covering around it, and you see the evidence before you commit to anything.

Often the fix is small: a seal, a flashing or a handful of tiles rather than a whole new window. Our roof window and skylight pages show the larger jobs too.