Updated
Dirty Roof Windows And Skylights
Loft and bathroom roof windows have gone grey and green outside, and the room has lost its daylight.
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What's happening?
Roof windows get dirty faster than anything else in the house and are cleaned least. They face the sky, so they collect everything that falls — pollen, moss spores from the tiles above, leaf debris, bird droppings and airborne grime — and their shallow pitch means rain sits and evaporates rather than running off, leaving mineral spotting on top of the organic film. Many roof windows pivot fully so the outer face can be cleaned from inside the room, which is the safe method and the one most owners do not realise exists. What people should not do is go onto the roof. Roof lights and the surrounding tiles are precisely the fragile surfaces HSE identifies for falls, and a fall through a roof window is a fall into the room below.
What usually causes it?
- A near-flat pitch holding rainwater until it evaporates, leaving mineral spotting
- Moss and lichen debris washing down from tiles and slates above the window
- Leaf litter and seed cases collecting in the flashing kerb around the frame
- Pollen and airborne grime settling on an upward-facing pane
- Bird droppings from a ridge, aerial or chimney perch directly above
- Blocked flashing and drainage gaps around the frame holding debris against the glass
- A blocked or dirty ventilation flap and filter, so the window cannot breathe
Is it dangerous?
The window is not dangerous; getting to it is. Roof windows, the tiles around them and any adjacent flat or fragile roof are surfaces people fall through, and HSE work at height guidance treats them as such. Standing on a roof to reach a skylight, or leaning out of one and holding the frame, are both how serious falls happen. There is also a practical risk in forcing a pivot mechanism that has seized — the sash can drop.
Can I fix it myself?
Often yes, from inside. Most modern roof windows rotate through 180 degrees and lock in a cleaning position, which puts the outer face inside the room at arm's length while you stand on the floor. Check your window's manual for the barrel bolt or catch that holds it there. Clean the pane, the flashing edge you can reach and the ventilation filter. Do not climb onto the roof, do not lean out of the opening, and do not force a stiff or seized pivot — that is a repair, not a cleaning problem.
When should you call a window cleaner?
Call a window cleaner when the window will not pivot to a cleaning position, when it is a fixed roof light, when there is heavy moss and debris in the flashing that needs clearing properly, or when the run of skylights is on a pitch nobody should be walking. They will work from the ground with a pole, or from proper access, rather than from the tiles.
What will the window cleaner actually do?
- Clean the outer pane from inside via the window's cleaning position where the design allows it
- Reach fixed and inaccessible roof lights from the ground with a water-fed pole, or from proper access equipment
- Clear moss, silt and leaf debris out of the flashing kerb and drainage gaps around the frame
- Clean the ventilation flap and filter so the window can ventilate again
- Rinse with deionised water so an upward-facing pane dries without mineral spotting
- Report a seized pivot, perished gasket, misted unit or damaged flashing rather than cleaning around it
Frequently asked questions
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Sources & References
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