Start by separating water entry from condensation
The timing, weather, wind direction, interior humidity, and location of the moisture matter. A stain below a skylight can also come from a roof penetration or seam above it.
What the inspection should consider
- Deck-mounted versus curb-mounted construction
- Age and condition of glazing, seals, frame, and cladding
- Manufacturer-specific flashing components
- Head, sill, side, and step flashing integration
- Condition and remaining life of surrounding roofing
- Ice, snow, debris, and drainage patterns
- Interior shaft insulation and air sealing
When repair may be reasonable
A repair may make sense when the skylight itself is serviceable and the failure is a localized, accessible flashing or roofing detail that can be integrated durably. The company should explain exactly what it will open and replace.
Surface sealant alone should not be presented as a universal permanent fix. Some designed joints use sealant, but missing or poorly integrated flashing generally requires a detail-level repair.
When replacement deserves consideration
Replacement becomes more practical when the unit has failed, is near the end of its serviceable life, lacks compatible flashing components, or will soon be surrounded by a new roof. Coordinating skylight and roof work can avoid reopening new roofing later.
Roof age changes the repair decision
Opening a brittle or near-replacement roof around a skylight can make a limited repair harder to integrate. If reroofing is expected soon, replacing an aging skylight at the same time may avoid removing new roofing later.
The opposite is also true: a newer skylight with a localized flashing issue should not automatically be discarded. Ask for the condition of the unit and surrounding roof to be explained separately.
Details to put in writing
- Skylight manufacturer and model when identifiable
- Deck-mounted or curb-mounted configuration
- Flashing kit and underlayment included
- Interior shaft, trim, paint, and insulation included or excluded
- Temporary weather protection during work
- Product and workmanship warranty responsibilities
Establish whether it is water or condensation first
Condensation is misdiagnosed constantly, because a skylight is a cold surface in a warm room and behaves like a window on a January night. It presents seasonally rather than with rain, and it is repeatedly repaired as a leak with no effect.
| When moisture appears | What it is | What fixes it |
|---|---|---|
| Wind-driven rain from one direction | Flashing at the head or sides | Reflash with the manufacturer's kit for that unit |
| Any rain, consistently | Failed seal, glazing, or no flashing kit | Repair or replace the unit and correct the flashing |
| A thaw after snow, never in summer | Ice damming around the curb | Attic air sealing and insulation; membrane at next reroof |
| Cold weather with no precipitation | Condensation on cold glazing or an uninsulated shaft | Insulate and air-seal the shaft; manage indoor humidity |
The decision that saves the most money
If the roof is due for replacement and the skylight is already well into its service life, replace them together. Reusing an aged skylight under a new roof is one of the most common ways a sound new roof develops a leak, and replacing it afterwards means opening the new roofing to do it.
Ask for the skylight priced as a clearly itemised option in the roofing proposal. The marginal cost while the roof is open is far lower than the cost of a separate later project.
Published August 12, 2026 and last reviewed August 16, 2026 by Greater Burlington Roofing. General roofing information; an on-site inspection is required for property-specific recommendations.