Velux and roof window fitting and repair

Velux window fitting and roof windows generally let light into a loft conversion or attic room, but they are also one of the more common places a pitched roof actually leaks, because the flashing kit sealing the window into the surrounding tiles has to be fitted exactly right to shed water in every direction. Get that wrong and no amount of resealing the glass will fix it.

New installation

Fitting a new Velux or equivalent roof window means cutting the roof structure correctly, forming a proper weathertight opening with new rafters trimmed to size, and fitting the manufacturer's flashing kit matched to your roof covering, tile, slate or flat, since each has a different kit. Done properly it is completely watertight from day one. We fit it as part of loft conversions and as standalone jobs.

Why roof windows leak

• The wrong flashing kit fitted for the tile or slate profile
• A flashing kit installed without the correct overlap sequence, letting water track sideways underneath it
• Perished rubber seals around the glass unit itself, usually after 15 to 20 years
• Cracked or lifted tiles immediately around the window opening
• Condensation mistaken for a leak, which is a different problem entirely and usually a ventilation issue rather than a water ingress one

Because the causes look similar from inside the room, we inspect the window from outside first before doing anything, rather than guessing based on where the stain appears on the ceiling.

Positioning and light

Where a new roof window is going in as part of a loft conversion or attic room, position matters as much as installation quality. Getting the window centred correctly on the room below, at a height that gives a usable view rather than just sky, and sized appropriately for the roof pitch, all affect how much the room is actually used afterward. We talk this through before cutting into the roof structure, since it cannot easily be moved once fitted.

Trickle vents and ventilation

Most roof windows include a trickle vent as standard, a small ventilation gap that lets fresh air into the room without opening the main window. Blocking or painting over this, which we see on older installations, can contribute to condensation building up in the room, sometimes mistaken for a window leak. We check this is clear and functioning as part of any inspection or repair.

Repair or replacement

A failed seal or a flashing kit fitted incorrectly can usually be repaired without replacing the whole unit. Where the window itself has failed, glass unit fogging, frame rot, or it is simply an old single glazed unit, replacement with a modern equivalent improves both weathertightness and energy efficiency.

What you get

Every installation and repair carries our 10 year written workmanship guarantee, and we use manufacturer flashing kits matched correctly to your roof covering, not a generic universal kit that fits nothing properly.

What happens on the day

For a new installation, the roof structure is opened up to the agreed size, trimmed rafters fitted where needed to form the opening, the window unit installed and the manufacturer flashing kit dressed in following the correct overlap sequence with the surrounding tiles or slates. Internally, the reveal is finished ready for plastering or lining. For a repair, the surrounding tiles are lifted, the flashing corrected or resealed, and everything checked for a proper weathertight finish before we leave.

Blinds and accessories

Manufacturer blinds, whether blackout or ventilation blinds, fit directly to the window frame and are worth ordering at the same time as installation, since some fit into recesses built in during manufacture and are far easier to add before the surrounding plasterwork is finished than afterward. We can advise on this at the inspection stage if it is relevant to your job.

Multiple windows in one loft conversion

Where a loft conversion needs several roof windows, we plan the whole layout together rather than fit each one in isolation, since spacing, alignment and matching sizes across a run of windows makes a genuine difference to how the finished room looks and how evenly it is lit. This is worth discussing before the roof structure is opened up, not decided window by window as the job proceeds.

The finished internal reveal is checked square and true before we leave, so plastering or lining the opening afterward gives a clean, professional result rather than one that needs correcting later.

Areas we cover

Velux and roof window work across Wisbech, Norwich, Cambridge, Ely and the rest of Cambridgeshire, Norfolk, west Suffolk and south Lincolnshire. If the issue turns out to be condensation rather than a leak, see our condensation in the loft guide, or our roof repairs page if it is a wider roof problem rather than the window itself.