How do you clean the outside of a roof window?
From inside the room, in almost every case. A centre pivot roof window rotates through most of a half turn and locks in that position with a barrel bolt at the head, bringing the outer face of the glass into the room where it can be washed standing on the floor. Warm water, a little washing up liquid, a soft microfibre cloth, then a dry cloth. Five minutes a pane.
That rotation is one of the quiet reasons roof windows are specified over fixed panels in a slope. Nobody goes on the roof, nobody leans a ladder against a frame, and the job gets done in the middle of winter as easily as in June. What follows covers the rotation, the top hung variation, what to keep away from the glass, and the parts around the pane that matter more than the pane does. The units themselves are covered under VELUX window installation.
Rotating the sash, and the bolt that holds it there
Open the window on the top handle, then take the sash and swing it through until it has turned roughly one hundred and eighty degrees. At that point a barrel bolt or catch on the side of the frame engages into the sash and holds it, which is the part people miss. Engage it every time. An unlatched sash resting on its friction hinges will move if it is leaned on, and it moves in the direction of your hand.
With the bolt in, the outer face is presented to the room at a comfortable working angle. Do the glass first, then the outer face of the sash and the drainage channel along its lower edge, which collects grit. Release the bolt, swing back, and check the handle latches properly before walking away.
Top hung windows, and the second hinge point
A top hung sash does not rotate the same way, because the hinge is at the head. Most units get round this with a secondary pivot: the sash can be swung out on the top hinge, then released on a side catch and rotated on a lower pivot point into the cleaning position.
The mechanism differs by manufacturer and by generation, and it is the one part of the operation worth reading the instructions for once. On some older top hung units the rotation is stiff on a cold day and easier after the frame has warmed. On escape variants the sash swings wide rather than rotating, and the outer face is then reached by leaning through, which is manageable on a single storey slope and not on a second floor one.
What to use, and what marks the glass
What works: warm water with a small amount of washing up liquid, a soft microfibre cloth or lambswool applicator, and a second dry microfibre for the finishing pass. Filtered or distilled water leaves fewer spots than hard Essex mains water, which is worth knowing on a sunny day.
What to keep away from the pane: wire wool, melamine sponges, scouring cream, bleach, solvent cleaners and any blade. All of them will mark a self-cleaning or solar control coating permanently, and the coating is applied at the factory and cannot be put back. Keep pressure washers away 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 the pane so it dries without streaks
Wet the whole pane and leave it a minute so the film softens before any pressure goes on it. Then work from the top of the sash downwards in overlapping passes, so dirty water runs onto glass you have not finished rather than onto glass you have.
Dry immediately with the second cloth, working the edges and the gasket line last. Water left standing in the corner of a gasket is where ring marks come from. Do the job on an overcast day if you can. Low sun through the glass dries it before you have finished the stroke and makes streaks impossible to judge until they have set.
The gasket, the drainage slots and the ventilation flap
While the sash is rotated, three things are within reach that never otherwise are. The perimeter gasket wants a wipe and a look: it should be supple and sitting evenly in its groove, not flattened or displaced at a corner.
The drainage slots along the bottom of the outer frame let condensation and driven rain escape. They block with dust, moss and insect debris, and a blocked slot backs water up against the gasket. Clear them with a soft brush. And the ventilation flap under the handle has a filter in it that collects a felt of dust over a few years, which is lifted out, rinsed and put back.
The flashing and the tile course below the window
This is the part that actually earns the time. Below the sill of the window sits an apron flashing dressed over the covering, and above the head there is a drainage gutter formed by the flashing that takes water round the unit.
Both collect leaves, moss and silt, and once that dam holds water the covering below is standing in it. Where the window is reachable from a garden with a pole, clearing the head gutter each autumn is the single most useful five minutes available. Where it is not reachable, it goes on the list for whoever is next on the roof. Most water problems that appear around a roof window begin as a drainage route that quietly closed itself.
Frequency, and what the slope does for you
Twice a year suits most sites: once in late autumn once the leaves are down, once in spring after the winter grime. A window on a steep Victorian rear slope stays cleaner than one on a shallow interwar hip, because run-off is faster and carries more away with it.
Local conditions shift the interval. Slopes under a mature lime pick up honeydew, which is sticky and holds everything else. Sites near arable land east of Chelmsford take dust at harvest. Properties on the Blackwater and around Canvey get a salt film that dulls glass faster than inland houses. The test is honest and simple: look up on a bright day, and if the sky has gone milky it is time.
Self-cleaning coatings on a sloping pane
Many units 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 rather than beading, carrying the loosened material off with it.
On a pitched slope it works better than on a flat panel, because run-off has somewhere to go. It does not remove the job. Bird droppings, tree sap and building dust still want washing off, and a window in a sheltered spot that rarely gets direct rain will still film over. Treat it as roughly halving the frequency. Ordinary washing up liquid does no harm to it; anything abrasive ends it.
Windows out of reach, and the sensible limit
The rotation handles almost everything, which is why height is rarely the problem it is with a flat panel. Where it does become one is on a window whose handle is above comfortable reach, in a room with a raised platform, or on an escape unit that swings rather than rotates on a second floor slope.
A telescopic pole with a microfibre head reaches a high handle for the inside face, and an electric opener solves the operation permanently. Leaning out of a rotated sash on an upper floor, or standing on the covering to reach the outside, is where both the glass and the person come to grief. Sunspire looks over the perimeter detailing whenever it is on site, and the ten-year workmanship guarantee sits behind that detailing rather than behind any 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