Water appearing near a skylight or roof lantern does not automatically mean the whole flat roof has failed. The first job is to identify whether water is entering through the roof covering, the junction around the unit, a seal or another detail.
Why leaks appear around roof lanterns and skylights
These areas contain multiple junctions and changes in level. Water can enter at a local defect and travel before becoming visible inside, so the damp mark below is not always directly beneath the entry point.
What to check
- Look for visible cracks, splits or lifted edges in the surrounding roof covering.
- Inspect the junction between the flat roof and the rooflight or lantern.
- Check whether the problem is worse during wind-driven rain.
- Look for ponding or poor drainage near the unit.
- Check the surrounding deck for softness or movement without taking unsafe risks.
Roof defect or rooflight defect?
If the roof covering around the unit is sound, the leak may originate from the rooflight assembly, glazing, seals or associated detailing rather than the waterproof roof surface. That distinction matters because coating the surrounding roof will not repair a defect within the rooflight itself.
When a local reinforced repair may make sense
If diagnosis identifies a genuinely localised defect in a compatible roof surface and the surrounding roof and deck remain sound, a reinforced liquid repair may be considered. The repair area needs correct preparation and any required primer before liquid waterproofing and reinforcement are applied.
For an appropriate local defect, see the SealForge Kit — £129.99 plus delivery.
When to get professional help
Use a competent professional where the leak source remains uncertain, the rooflight assembly itself requires dismantling, there is widespread deterioration, the deck is soft or sagging, or access is unsafe.
Continue diagnosis in the Flat Roof Leak Help Centre.