Skylight Window Repairs London: Leaks, Hinges and Faults

Skylights and roof windows bring natural light into a property, but problems with seals, hardware or surrounding roof details can affect their performance. A leaking skylight does not always mean the entire window needs replacing — the correct solution depends on the window design, the source of the leak and the condition of the surrounding roof.

What This Guide Covers

• A leaking skylight may be caused by failed flashing, blocked drainage or deteriorated seals — not always the glass
• Hinge and opening mechanism repairs depend on the manufacturer, model and availability of parts
• Gas strut replacements must match the exact force rating and mounting dimensions of the original
• Do not climb onto a roof without suitable training, equipment and safe access arrangements
• Provide the manufacturer name, model number and photographs to help identify the correct parts

Introduction

London homeowners face unique challenges when it comes to glazing — from period properties with sash windows in conservation areas, to modern developments requiring structural glass installations. Getting the right advice before you commit can save you significant time and money.

At BuilderFix Glazing, we have completed thousands of glazing jobs across Greater London and Surrey — from emergency repairs in Kensington and Chelsea, to bespoke walk-on glass installations in Mayfair and Belgravia. This guide is based on real experience and the questions our customers ask us most often.

In Depth

Skylights and roof windows are exposed to more severe weather than vertical windows. Rain, wind, frost and UV degradation all act on the seals, flashing and hardware continuously. The most common complaint is water ingress, and the most important point about skylight leaks is that the water visible inside the property may not enter at the point where you can see it. Water can travel along roof timbers, down insulation, and across sarking boards before dripping through a ceiling several metres from the actual entry point.

Velux is the most common manufacturer in London properties, and their windows — including the GGL, GGU and F-series roof windows — have a well-developed repair parts system. Replacement flashings, seals, hinges, handles, and gas struts are available for most models still in production, and for many discontinued models. The critical information is the model designation (printed on a label inside the window when open) and the installation size. With this information, the correct parts can be identified precisely.

Flashing is the most common cause of skylight leaks in older installations. The flashing kit — the system of lead or aluminium sections that form a weathertight junction between the window frame and the surrounding roof covering — deteriorates over 20–30 years. Lead flashings can crack, pull away from the frame or be displaced by freeze-thaw cycling. Aluminium flashings can corrode at the joints. When flashing fails, water enters between the window frame and the tile or slate surface and tracks into the roof structure. Replacing the flashing requires removing the tiles around the window perimeter, fitting the new flashing kit and relaying the tiles — roofing work that requires care and the correct fixings.

Hinge and opening mechanism failures are more common in frequently used roof windows. A Velux window opened and closed daily accumulates more wear in ten years than one opened only in summer. Common hinge faults include broken hinged arms, worn pivot bushings and fractured plastic carrier components. Gas strut failure presents as a window that will not stay open or falls shut under its own weight. Strut replacement requires matching the original strut length, end fitting type, gas pressure rating and compressed/extended dimensions — an incorrect strut may prevent the window from operating safely or may not physically fit the mounting points.

Sealed unit replacements in roof windows follow the same principles as vertical double glazing, with one important addition: glazing installed at an angle less than 15 degrees from horizontal is classified as overhead glazing under BS 6206 and must use laminated safety glass. If the original sealed unit was laminated and the replacement is specified in standard toughened glass, this is a compliance failure. Always confirm the safety glass specification before ordering.

What Does This Typically Cost in London?

Costs vary depending on the type and size of work, the glass specification, frame material, and access. As a general guide, always obtain a free written quote before committing — this protects you from unexpected charges.

At BuilderFix Glazing, we provide free, no-obligation written quotes for all work. Our prices are transparent and fixed before we start — no surprises on the invoice.

What to Ask When Getting a Quote

• Is the price fixed, or could it change once work starts?
• What glass specification is included?
• Are all fixings, sealants and finishing included?
• What compliance documentation will I receive?
• What happens if there is an issue after completion?