Quick answer: a leaking roof window is not always a failed window. Water can enter through the flashing kit, surrounding tiles, blocked drainage channels, poor roof pitch, condensation, or a roof defect above the window.
- Check whether the leak happens during rain, after cold nights, or only when wind drives rain across the roof.
- Look for stains at the top corners, sides and lower frame. The position helps separate flashing issues from condensation.
- A proper repair should inspect the window, flashing, underlay, tile cuts and roof covering above the opening.
Why skylight leaks are often misdiagnosed
A roof window is a break in the roof covering, so it depends on the window frame, flashing kit and surrounding tiles or slates working together. Water seen on the frame may have entered above the window and tracked down under the covering.
Condensation can also confuse the diagnosis. Warm indoor air meeting cold glass or frame surfaces can create water inside the room, especially in bathrooms, kitchens and poorly ventilated loft conversions. That is a different problem from rainwater entering through the roof.
Common causes of roof window leaks
The most common rainwater causes are damaged flashing, blocked side channels, poor tile cuts, slipped tiles above the window, failed underlay, or a window installed below the pitch range expected by its flashing system. On flat roofs, upstands and drainage around the rooflight become the key details.
If the leak appears after new insulation or loft work, ventilation should also be checked. Our guide to roof condensation after insulation explains why damp can appear even without a hole in the roof.
How to inspect without guessing
A roofer should check the roof covering above the window first, then the flashing and drainage channels, then the frame seals and internal finish. If the surrounding tiles or slates are loose, repairing only the window seal will not solve the leak.
For pitched roofs, the inspection overlaps with skylight and roof window installation, slate and tile roofing, and general roof repairs.
When a replacement is better than a repair
A repair may be enough when the flashing is blocked, a tile has slipped or a local detail has failed. Replacement becomes more likely when the frame is rotten, the glazing unit has failed, the window is poorly matched to the roof pitch, or the surrounding roof needs wider work.
If the window sits in an old roof near the end of its life, use the decision framework in Repair or Replace: When a Kent Roof Has Reached the End before spending money on repeated local fixes.
FAQs about leaking roof windows
Why does my skylight leak only in windy rain?
Wind-driven rain can push water into weak flashing, poor tile cuts or gaps above the roof window that stay dry in normal rain.
Can condensation look like a roof window leak?
Yes. Condensation often appears on the inside face of the glass or frame, especially in humid rooms. Rainwater leaks usually follow weather and roof details.
Do I need a new roof window if it leaks?
Not always. The issue may be flashing, blocked drainage, surrounding tiles or underlay. Replacement is more likely when the frame or glazing has failed.
Should a roof window be repaired by a roofer or window fitter?
If the issue involves flashing, tiles, underlay or roof pitch, use a roofer. The window and the roof covering need to be assessed together.
Kent Roofing Services can inspect leaking skylights, roof windows and surrounding roof defects across Kent. Contact us to arrange an inspection.
