How do you clean the outside of a roof window?

Centre pivot

Open the window, then rotate the sash through about 180 degrees until the outer face is inside the room. There is a catch, usually a slider or a bolt at the top of the sash, that locks it in the rotated position so it cannot swing back while you are working.

Find that catch before you start. It is the difference between a safe job and an awkward one.

Top hung

Better units also rotate for cleaning, using a separate release that converts the top hung action to a pivot. Simpler units do not, and on those the outside has to be reached from a ladder or with a pole.

If cleaning from inside matters to you, check this before ordering, because it is a real difference between models at similar prices.

What to use

Warm water with a little detergent, and a microfibre cloth or a squeegee. Nothing abrasive, and no solvents on the frame or the aluminium cladding, because damaging the coating is how corrosion starts, particularly near the coast.

Twice a year is plenty for most. More under trees, and more near the sea where salt film builds up.

Do not

Lean out of the opening to reach the glass. Climb onto the roof to clean a window that rotates. Or use a pressure washer, which drives water past seals that were designed for rain rather than a jet.

While you are there

Wipe the seals, clear leaves and moss from the head flashing above the window, and check the ventilation filter. Ten minutes, once a year, and it materially extends the life of the unit.

From inside, if the window pivots

A centre pivot roof window rotates fully so the outer face turns inward, and most designs have a catch that holds the sash in that position while you clean it. That is the intended method and it is why centre pivot remains popular despite the sash obstructing the opening when open.

Ordinary glass cleaner and a soft cloth. Take the opportunity to wipe the gasket at the same time, because grit on the compression seal is what stops a sash seating and gets reported as a leak.

If it does not pivot

A top hung window swings outward and cannot be rotated. On a first floor rear slope you can frequently reach the outer face by leaning out through the opening, which is fine if you can do it safely and without leaning your weight on the sash.

Higher than that, the options are a telescopic pole with a soft brush head, ideally water fed, or access from outside with a tower.

Some models are dual action, opening top hung for use and pivoting for cleaning. On a high level window that is worth the premium and it should be decided at order stage.

Self cleaning glass

Genuinely useful on a pitched roof window, because the coating breaks down organic deposits and rain sheets off rather than beading, carrying them away.

It reduces the frequency rather than removing the job, and it does very little on a near flat unit where water sits rather than runs.

What not to do

Do not stand on the roof unless it is safe and you know it will take you. A rooflight is not something to stand on at all unless it is specified as walk on.

Do not pressure wash at close range. It drives water into the perimeter seal and can damage coatings.

Do not use abrasives or scourers, which mark glass and destroy self cleaning coatings.

Do not lean a ladder against the window. The frame is not designed to carry a point load and the glass certainly is not.

How often

On a steep roof with rain doing most of the work, once a year is plenty. Under trees, or on a shallow pitch, twice.

North facing slopes hold algae more readily because they dry more slowly, so they benefit from a clean when the gutters are done.

The rotating sash, and why it exists

A centre pivot roof window rotates through most of a half turn and locks in a cleaning position, bringing the outer face of the glass inside the room. That is the design intent and it is the safe way to do it.

The barrel bolt or catch that holds it there is not optional. Cleaning a rotated sash that is not locked risks it swinging back with your hands and head through the opening.

On a top hung window, most models can also be rotated for cleaning by releasing a catch, though the action differs by manufacturer and it is worth reading the instructions once rather than forcing it.

The right cleaning materials

Warm water, a little washing up liquid, a soft cloth or microfibre. Rinse and let it dry rather than polishing it dry, which is what leaves streaks.

Nothing abrasive, and no solvent on the frame or the external cladding.

While the sash is rotated, wipe the gasket and the drainage channel at the sill. Debris there holds water against the seal and is the commonest cause of a window that starts letting water in after fifteen uneventful years.

How much a coating helps

Reduces the frequency rather than removing the need. It needs rain running off it to work, so it performs well on a steeper roof and less well on a shallow one. Do not use abrasives on it, which destroy the coating permanently.