Velux window repairs: what can be fixed

Most Velux window repairs start with working out what the problem really is. A leak is often the roofing around the window, condensation is often humidity in the room, and only some faults sit in the window itself. The manufacturer’s own support advice is a good place to start, and this guide explains what it says and when to repair and when to replace.

Find the cause before you repair a Velux window

VELUX says that water entering through one of its windows is not common, and that several things can make water visible inside. Before you call anyone, check three things it lists:

• the window is fully closed and locked;
• the water isn’t condensation;
• there is no obvious damage or loose covering on the outside of the window.

For flat roof windows, VELUX says the most common cause is the roofing material and the weathering around the window frame, and it suggests the original installer or a roofer checks them. The same logic is sensible on a pitched roof. Water around a roof window may be coming from the flashing or the tiles, so the person to check them is a roofer, and replacing the window won’t cure it.

Condensation: humidity or a failed unit

On its support page about condensation, VELUX says that condensation is a natural phenomenon and not a product issue. It is a sign of high humidity in the room, and the remedy is more ventilation. It is usually more noticeable on roof windows because warm, moist air rises to the ceiling.

Mist trapped between the two panes of the glass is different. That means the seal on the sealed glazing unit has failed, which our guides to sealed units in wooden frames and sealed unit replacement explain. I haven’t found VELUX guidance on replacing a glazing unit on its own. Ask VELUX or an installer, with your window’s type plate details to hand, whether a replacement unit is available for your model.

Wear: seals, hinges, handles and parts

Some faults are simply wear. Draughts often point to perished seals, and stiff opening to hinges or handles that need attention. VELUX’s care and maintenance page says you need the details on the window’s type plate to find the right instructions. It sells maintenance kits for things like replacing an air filter, repairing a scratch and lubricating hinges. It also recommends replacing gas springs and motors on a schedule, which you will find in its care guide.

Check the type plate first, because every repair, and every part, depends on it.

Repair or replace a Velux window

My rule of thumb is that if the frame is sound and the fault is specific, repair usually makes more sense. A failed seal, a leaking flashing, a worn hinge or a stiff handle can each be put right without disturbing the rest of the window.

Replacement makes more sense when:

• a timber frame is rotten;
• several parts have failed at once;
• you are planning major work on the roof;
• you want a different specification, such as electric operation.

If you do replace the whole window, ask the installer how the work will be certified. The Planning Portal says that building regulations apply to all replacement glazing. I haven’t found guidance that says whether a repair such as new seals or flashing needs approval, so ask your council’s building control if you are unsure.

What a Velux repair costs

Prices depend on the type of repair, the size of the window and how easy it is to reach. Access matters on a roof, because scaffolding can be a real part of the bill. Checkatrade publishes a Velux window repair cost guide with typical ranges for seals, flashing, mechanisms and full replacement. Treat any figure as a guide and ask for a written quote.

What to ask a repairer

Before you agree to a repair, ask:

1. Have you identified the cause, and is it the window or the roof?
2. Can you get the parts for my model, using its type plate details?
3. What will you do if the leak is in the flashing or the tiles?
4. What guarantee do you give on the work, in writing?

Put any quote through our quote checker, and see windows explained for how other parts of a window fail.