Planning Notes
Work out whether your skylight needs a simple repair, new flashing, or a complete replacement before anyone goes up on the roof.
A leaking or ageing skylight can point to three different problems—and the fix depends on which one it is. The seal around the frame might be worn out. The flashing underneath might be rusted or separated. Or the glazing itself might be cracked, or the frame rotted. The location of water stains, how long the skylight has been in place, and whether recent roof work disrupted the seal all point toward the real culprit. This guide asks a few questions you can answer from the floor or a short ladder, and returns a triage: what to watch, what your contractor should check first, or when to call immediately because water is already in the ceiling.
This is triage, not diagnosis. Only someone on the roof confirms what is actually broken. But the questions here tell you what to look for, what to write down, and what to ask about on the phone when you call.
What does the skylight show?
Answer these questions from inside, looking at the frame and the ceiling around it. If you cannot see the frame (it is above a ceiling and you only see the light), answer based on what shows at ceiling level.
Only someone on the roof with the frame open can confirm the cause. Use this to know what to ask about.
| What you see | Likely culprit | Next step |
|---|---|---|
| Moisture at the frame, any rain | The frame or dome seal | Call a skylight contractor to inspect and reseal it |
| Stain spreading from the frame, heavy or wind-driven rain | Flashing underneath | A contractor should inspect the flashing and re-seal or replace it |
| Stain, snowmelt or standing water | Flashing or slope | A contractor should check whether water is pooling above the skylight |
| Stain on old skylight | Glazing or frame damage | You will likely need to replace the skylight. Get contractor quotes. |
| Moisture during fog or high humidity | Condensation, not a leak | Watch for mould; improve ventilation in the room |
| Water pooling or dripping fast | Urgent: ceiling or unit damage | Call immediately; water in the ceiling causes fast damage |
| This table is a starting point. The exact cause depends on the roof structure, the age of the seal and flashing, the type of roofing around it, and what work was done before. | ||
The order to work through it
Numbers that change the picture
- 5
- Typical questions to answer before calling
- 3
- Most common failure points: seal, flashing, unit
- 20
- Years a typical skylight seal lasts before it fails
What drives the decision
The age of the seal, the condition of the flashing, and whether water has already reached the ceiling all point toward repair or replacement. A seal that is failing but the flashing is intact might need only resealing. A flashing that is rusted or separated needs replacement, whether the seal is good or not. And if water is already in the ceiling, waiting costs money in mould and rot.
