The short answer
The faults we see in VELUX roof windows come down to a short list: cloudy glass between the panes, damp on the lining, a sash that sticks or will not stay open, draughts round the seals, and a brown stain under the frame. Each has its own cause, and the cause decides whether the window can carry on. Mist inside the sealed unit, soft timber at the lower corners and a leak at the flashing usually mean a new window with a fresh flashing kit.
- Free survey, fixed written quote
- 10-year workmanship guarantee
Mist, damp and drips: telling them apart
Water on a roof window can be in three places, and each place points somewhere different. Droplets on the room face of the glass are condensation: warm indoor air meeting a cold pane, as happens over a bathroom, a kitchen or a bedroom slept in with the door shut. That is a ventilation and lining question. The window itself may be sound.
Cloud, a milky film or beads between the two panes is a different matter. The sealed glass unit has let air in, and no wiping reaches it, because the moisture sits between the inner faces of the glass. Our notes on why rooflights mist up follow that failure in detail.
A drip or a brown tide mark under the frame is the hard one to read. It may be rain getting past the flashing, or condensation that has run down the glass and gathered at the sill. A stain that appears only after a downpour points to the flashing. A stain that comes with cold, still mornings points to condensation. Until the lining is opened up the two can look the same.
| What you see | Usual cause | What it asks for |
|---|---|---|
| Beads on the room side of the glass | Warm damp air meeting a cold pane | Better ventilation and a sealed, insulated lining |
| Cloud between the two panes | Failed seal in the glazed unit | A new window |
| Stain below the frame after heavy rain | Water past the flashing or the tile cover | Flashing and surround opened up and checked |
| Soft, flaking paint at the lower corners | Water sitting on a timber frame | A new window if the timber has gone |
Sticking sashes, loose handles and cold draughts
A sash that is stiff to lift, will not stay where you leave it or drops back on its own has a worn mechanism. Handles loosen the same way. After many years of weather the hinges and pivots on the frame have simply done their miles.
Draughts come from two places. Seals that have perished let air whistle round the sash in a gale, and you can feel the cold on your hand held along the edge on a winter morning. A frame that has moved out of square stops the sash closing evenly onto its seals, which leaves a gap on one side even when the seals themselves are sound. Timber frames add a third cause: if a screwdriver tip sinks into the paint at the lower corners, the wood beneath has rotted.
Electric and solar models bring one more symptom. If the window has stopped answering the remote, check the control batteries and wipe any dirt from the solar panel before anything else.
Myth
A window that drips must have a faulty flashing.
Fact
Condensation running down cold glass makes the same drip. The glass, the lining and the flashing all get looked at before any one of them takes the blame.
When a new window is the answer
One fault on its own does not always end a window's life, but several together do, and a failed sealed unit, rotten timber or a frame out of square will not come good. Then the sensible move is a new window, a new flashing kit and a new lining in one job, which also puts a dry surround behind the frame. The job is followed in order in swapping an old VELUX window.
The frame carries a label with a size code such as MK04, where the letters give the width and the digits the height. It tells us the nearest current size, and the quote is built on it. A new or replacement roof window also has to meet the window limit of 1.4 W/m²K under Part L (or Window Energy Rating band B), a figure an older double-glazed unit may well fall short of. The rest of the range is on the VELUX windows page, and the skylight Building Regulations guide explains the energy rules.
What to send before we visit
Two photos help most: one of the window from inside, with the stain or the cloud in view, and one of the label on the frame. Note when the fault shows, whether on cold mornings or only after rain, because that points us to condensation or to the roof covering. Nothing is charged for the visit, and what you receive afterwards is a fixed written quote. Ask for a survey, or WhatsApp 07880 284133 with the photos.
