Skylight Leak Repair
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Skylight leak repair is the diagnosis and fixing of water intrusion around a roof skylight, typically costing $150–$800 for a repair and $900–$2,500 for a full skylight replacement, with most repairs completed in two to four hours. The first and most important step is identifying which of three very different problems you actually have: condensation (a ventilation issue, not a leak), a flashing failure around the skylight (a roof repair), or a failed seal in the skylight unit itself (usually a replacement). Misdiagnosing condensation as a leak — or caulking over a flashing failure — wastes money on repairs that cannot work.
Skylight Leak Repair Starts with Diagnosis: Condensation vs Flashing vs Failed Seal
Water appearing at a skylight has three distinct causes, each with its own fix:
| Symptom Pattern | Likely Cause | Fix | Typical Cost |
|---|---|---|---|
| Water droplets on the inside glass in cold weather, no rain needed | Condensation | Improve humidity control and ventilation | $0–$300 |
| Drips during or after rain, water at one corner or along the curb | Flashing or underlayment failure | Re-flash the skylight | $300–$800 |
| Fog, haze, or moisture between the glass panes | Failed insulated glass unit (IGU) seal | Replace glass or whole unit | $300–$2,500 |
| Water at the bottom edge in light rain, unit older than 15 years | Worn gaskets/weather seals on the unit | Reseal or replace unit | $150–$2,500 |
Condensation is the most common false alarm. Warm indoor air hits the cold glass and condenses, drips off the bottom edge, and stains the drywall exactly like a leak would. If moisture appears on dry, cold days — especially in bathrooms and kitchens — it is condensation. The fix is lower indoor humidity, running exhaust fans, and better attic airflow; see Roof Ventilation and the Attic Ventilation and Insulation Guide.
Flashing leaks follow rain. Water typically enters at the uphill side or corners of the skylight and may run along the light shaft framing before appearing. Tracing techniques are covered in How to Find and Fix Roof Leaks — a garden-hose test on each side of the skylight, one section at a time, isolates the entry point.
A failed IGU seal is unmistakable: permanent fog or condensation trapped between the panes that you cannot wipe off from either side. The glass has lost its insulating gas and seal. No roof repair fixes this.
How Much Does Skylight Leak Repair Cost?
- Resealing exterior gaskets and minor flashing touch-up: $150–$400
- Full re-flashing with a manufacturer flashing kit: $300–$800, depending on roof pitch, roofing material, and skylight size
- Replacing the glass (IGU only) on a quality curb-mounted unit: $300–$800
- Replacing the entire skylight: $900–$2,500 installed, including new flashing kit; large, venting, or electric units sit at the top of the range
- Interior drywall and finish repair after a leak: $200–$600 additional
Two cost rules of thumb. First, if the skylight is being re-flashed anyway and is more than 15 years old, replacing the unit at the same time usually adds only $300–$700, because the labor overlaps almost entirely. Second, if your roof is being replaced, always replace skylights with it — installing new shingles around a 20-year-old skylight is the most common way to end up cutting into a brand-new roof two years later. General context on repair pricing is in Roof Repair Costs.
How Is a Leaking Skylight Flashed and Repaired?
Modern skylights leak far less than their reputation suggests — when they are flashed with the manufacturer's kit rather than sealant. A proper repair restores that system:
- Curb-mounted skylights sit on a raised wooden curb (common on lower slopes and older homes). The repair involves removing surrounding shingles, installing new step flashing up each side of the curb, a head flashing across the top, an apron at the bottom, and self-adhering waterproof membrane beneath it all.
- Deck-mounted skylights fasten directly to the roof deck with a low profile and use an engineered, model-specific flashing kit. Repairs almost always mean installing the correct kit for that exact model — generic flashing and caulk do not reproduce the layered drainage.
- Weep holes matter. Quality skylights have small weep channels and holes designed to drain incidental moisture out of the frame. A surprisingly common "leak" is a previous owner or handyman having caulked the weep holes shut, trapping water inside the frame until it overflows indoors. Part of any repair is confirming the weeps are open.
The layering logic is the same as any roof penetration: every upper layer laps over the layer below so water always travels outward. The same principles appear in How to Repair Roof Flashing and How to Seal Roof Penetrations.
A note on DIY: applying fresh sealant to a visibly cracked exterior gasket is reasonable homeowner work, with appropriate products from the Roofing Sealants and Adhesives Guide and the precautions in the Roof Safety Guide for Homeowners. Re-flashing, however, involves opening up the roof around the unit; if shingle courses and membrane layering are unfamiliar territory, this is a job for a roofer. When to DIY vs When to Call a Roofer offers a sober way to make that call.
When Should You Replace a Skylight Instead of Repairing It?
Replace rather than repair when any of these apply:
- Age over 15–20 years. Gaskets, seals, and plastic components have a finite life. A 20-year-old unit that has started leaking will keep producing new failure points.
- Fogged or hazy glass. A failed IGU cannot be resealed economically; the glass or unit must be replaced.
- Cracked or yellowed acrylic dome. Older dome skylights become brittle and UV-degraded; replacement units are dramatically better insulated.
- Repeated leaks after a proper re-flash. If correctly installed flashing did not stop the water, the unit's internal seals are the problem.
- Roof replacement is scheduled. Replace skylights during the re-roof, every time.
- Energy performance. Pre-2000 skylights lose several times more heat than modern low-E, argon-filled units — in cold climates the energy savings partially offset replacement cost. See Energy-Efficient Roofing Systems.
Conversely, a quality skylight under 10–15 years old with a localized flashing failure is an excellent repair candidate — fix the flashing and expect many more years of service.
How Do You Prevent Skylight Leaks?
- Inspect the skylight's exterior sealant, flashing, and surrounding shingles once or twice a year — it is a standard item on a roof inspection checklist and worth special attention in the spring after freeze-thaw season.
- Keep the uphill side clear of leaves, needles, and snow dams; ponded debris against the head flashing is a leading leak trigger.
- Trim overhanging branches that drop debris and abrade the glazing.
- Control indoor humidity and keep bathroom/kitchen exhaust fans vented outside, not into the attic, to prevent the condensation that mimics leaks.
- In snow country, prevent ice dams from backing water up to the skylight — see How to Prevent and Remove Ice Dams.
- After any major hail or wind event, check the glazing and flashing as part of a Post-Storm Roof Damage Assessment; hail-cracked skylights are commonly covered perils on homeowner policies.
Quick Facts
| Metric | Value |
|---|---|
| Repair cost | $150–$800 |
| Replacement cost (installed) | $900–$2,500 |
| Typical repair time | 2–4 hours |
| Skylight unit lifespan | 15–25 years (replace at re-roof) |
| Most common false alarm | Interior condensation in cold weather |
| Most common true leak | Flashing/underlayment failure at curb or corners |
| Tell-tale sign of failed IGU | Fog between the glass panes |
| Key rule | Re-flash with the manufacturer's kit, never caulk alone |
Frequently Asked Questions
How much does it cost to fix a leaking skylight?
Skylight leak repair costs $150–$800 depending on scope: simple resealing runs $150–$400, while full re-flashing with a manufacturer kit costs $300–$800. If the unit itself has failed — fogged glass or worn internal seals — replacement costs $900–$2,500 installed, including a new flashing kit.
Why does my skylight only drip in winter with no rain?
That is almost certainly condensation, not a leak. Warm, humid indoor air condenses on the cold glass and drips off the bottom edge. Lower indoor humidity, run bathroom and kitchen exhaust fans, and improve attic ventilation. No roof repair will stop condensation, so diagnose before paying for flashing work.
Should I repair or replace a leaking skylight?
Repair when the unit is under 15 years old, the glass is clear, and the failure is in the flashing or exterior sealant. Replace when the unit is older than 15–20 years, the glass is fogged between panes, leaks recur after proper re-flashing, or a roof replacement is scheduled.
Can I just caulk a leaking skylight?
Caulk is only appropriate for a small, visible gap in otherwise sound exterior sealant, and it is temporary. Most skylight leaks are layered flashing failures that caulk cannot reach. Worse, caulking the frame's weep holes shut traps water inside and creates new leaks. Restore the flashing system instead.
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