A surprising number of reported skylight leaks are actually caused by internal condensation. Distinguishing between the two can save you time, stress, and money in unnecessary repair and call-out costs.
Is It Actually a Leak?
Not every dripping skylight is leaking rainwater. A significant number of reported leaks are actually caused by internal condensation. This is particularly common in high-humidity spaces such as bathrooms and kitchens, where poor ventilation can allow moisture to build up. Before assuming that the skylight itself is leaking, it is important to establish whether the water is entering from outside or forming as condensation internally.
Skylight condensation occurs when warm, moisture-laden indoor air rises and hits the cold surface of the glass, instantly turning invisible vapor into liquid droplets. This is especially common in high-humidity zones like bathrooms and kitchens.
However, glass surface temperature isn't the only trigger. Condensation can also form due to trapped air between the curb and the skylight itself. If air cannot circulate properly, a frequent issue when a curb is built too high or wide, or when the unit relies on a bulky framework typical in patent glazing systems, trapped moisture builds up and drips into the room below. Modern designs, such as Glazing Vision skylights, combat this by utilizing minimal framework alongside a dual-hardness EPDM insulating gasket to thermally isolate the frame from the building's interior.
The difference between condensation & leaks
To figure out what you are dealing with, you should track when and where the water appears for a clearer idea of the diagnosis.
Condensation Signs:
Location: Forms directly on the interior glass.
Timing: May occur without any rainfall, typically worsening in cold conditions or during high indoor activity (showering, cooking).
Impact: Results in fine mist, dripping, or light pooling on window sills.
Water Ingress (True Leak) Signs:
Location: Originates around the frame, flashing, curb, or surrounding drywall/ceiling.
Timing: Almost exclusively occurs during or shortly after heavy rainfall or melting snow.
Impact: Often leaves brown water staining, peeling paint, or drywall rot, and water may travel along roof timbers before becoming visible.
May travel before becoming visible
What to Do Next
A light misting on a freezing morning is not necessarily a sign of skylight failure, but persistent pooling, mold, or ceiling stains need immediate attention from your skylight manufacturer or a trusted, local skylight/roofing contractor.
Unsure if your skylight damage requires a simple seal fix or a full replacement? Download our free Skylight Leak Prevention Whitepaper for practical curb construction advice, diagnostic checklists, and more.
