Skylight Leak Repair & Precision Re-Flashing
The inherent Vulnerability of Skylights
A skylight is a brilliant architectural feature, flooding interior spaces with natural light and improving energy efficiency. However, from a structural engineering standpoint, a skylight is a massive, deliberate hole cut directly into your primary weather barrier. Because this opening is positioned precisely where water flows downhill, it acts as an obstacle. Water rushing down the slope of your roof slams into the upper edge of the skylight frame (the "head" flashing), forcing the installation to rely on a complex, multi-layered metal defense system to divert that water safely around the sides.
When a skylight leaks, homeowners immediately look at the glass or acrylic dome. While cracked glazing does occur, the reality is that over ninety percent of all skylight leaks have nothing to do with the glass itself. The failure almost always lies in the flashing—the intricate sheet metal weaving that connects the wooden skylight curb to the surrounding shingles or tiles. When this metal rusts, pulls away due to thermal expansion, or was improperly installed using cheap mastic sealants instead of properly fabricated step-flashing, water bypasses the curb and drips directly down the interior drywall shaft.
Repairing a leaking skylight is a delicate operation. It requires a contractor who understands both the hydrology of roof intersections and the specific manufacturer tolerances of modern skylight frames, ensuring the fix is structural rather than a temporary aesthetic cover-up.
Specialized Flashing Integration
To permanently stop a flashing leak around a curb-mounted skylight, professional technicians perform a complete "re-flashing." They do not rely on silicone caulk. First, the roof covering (shingles or tiles) extending two feet outward from the skylight in all directions is removed. The old, failed metal flashing is torn out. The technicians then apply an ice-and-water shield—a self-adhering, waterproof rubberized membrane—directly to the bare plywood deck, wrapping it entirely up and over the wooden curb. New aluminum or copper step-flashing is then woven piece-by-piece between the new shingles as they are re-installed, creating a cascaded water barrier. Finally, custom counter-flashing is secured over the top of the step-flashing, locking the entire assembly tight against the skylight frame.
8 Signs Your Skylight is Failing
1. Drips During Rainfall
The most obvious sign—water actively dripping from the corners of the skylight frame directly onto your floor.
2. Stained Drywall Shaft
Brown water rings or peeling paint on the vertical walls of the light tunnel leading up to the skylight.
3. Condensation Between Panes
A foggy, permanently opaque look in a double-pane glass skylight means the factory argon gas seal has blown.
4. Black Mold on the Frame
Dark spotting on the interior wooden trim surrounding the glass indicates chronic, slow moisture intrusion.
5. Rusted Exterior Flashing
Visible orange rust on the metal collar surrounding the exterior of the skylight curb.
6. Cracked Acrylic Dome
Plastic bubble skylights become brittle over time; a visible hairline crack will leak heavily during a storm.
7. Peeling Tar on the Roof
If a previous roofer smeared black tar around the base of the skylight, it will inevitably crack and fail as it dries out.
8. Drafts and Whistling
If you can feel cold air dropping from the skylight, the weather stripping or curb flashing is structurally compromised.
The Mechanics of Thermal Expansion
Skylights are particularly susceptible to the massive temperature swings of the Los Angeles climate. The glass pane (or acrylic dome), the aluminum frame holding the glass, the wooden curb, and the metal flashing all possess different rates of thermal expansion. On a 100-degree summer day, the aluminum frame expands rapidly, while the wood beneath it expands slowly. When the temperature drops 30 degrees at night, they contract at different speeds.
This constant push-and-pull creates immense shear stress on the rubber gaskets sealing the glass and the sealants securing the metal flashing. Over a period of ten years, this micro-movement slowly rips the sealant bonds apart, creating a gap just wide enough for capillary action to draw rainwater inside during the winter storm season.
Safe DIY Checks: The Condensation Test
Before assuming your roof is leaking, you must rule out indoor humidity. Skylights are essentially cold glass surfaces suspended above warm, humid interior air (especially if located near a bathroom or kitchen). In the winter, warm interior air hits the cold skylight glass, and the moisture in the air condenses into water droplets, which run down the glass and drip onto your floor.
The Test: Wait for a cold, dry morning when it has not rained for several days. If the skylight is dripping, or if the glass is covered in thick sweat, you do not have a roof leak—you have an interior ventilation problem. However, if the dripping only occurs exactly during or immediately after a rainstorm, the exterior flashing or weather seals have failed, and you need a roofing professional.
Most high-quality skylights are designed with small drainage slots (weep holes) at the bottom edge of the exterior frame. These are designed to allow incidental condensation to escape. Often, well-meaning homeowners or inexperienced handymen see these holes, assume they are the source of the leak, and fill them with silicone caulk. This traps the water inside the frame, rapidly rotting the wood curb and destroying the skylight permanently.
The Pro Repair Sequence
Diagnostic Trace
Using thermal imaging, the technician confirms whether the water is entering through the glass gaskets, the frame corners, or the perimeter flashing.
Shingle Removal
The shingles or tiles immediately surrounding the skylight are carefully removed to expose the wooden curb and the underlying decking.
Ice & Water Barrier
A secondary waterproof membrane is applied directly to the bare wood, running continuously up the sides of the curb to prevent wind-driven rain penetration.
Custom Re-Flashing
New metal step-flashing is woven into the reinstalled roofing materials, restoring the physical barrier that actively channels water safely around the unit.
Repair Cost Factors
Skylight repair costs depend heavily on whether the unit can simply be re-flashed, or if the unit itself is too old and degraded, requiring a full replacement.
| Factor | Impact on Complexity & Cost |
|---|---|
| Curb-Mount vs. Deck-Mount | Curb-mounted skylights sit on a raised wooden box, making flashing repair relatively straightforward. Deck-mounted skylights sit flush with the roof, requiring more invasive shingle removal. |
| Glass vs. Acrylic | If a plastic acrylic dome is cracked, the entire unit must be replaced. A high-quality Velux glass unit can often be saved by simply rebuilding the flashing around it. |
| Pitch of Roof | Working on steep-slope roofs requires specialized safety harnesses and scaffolding setups, slightly increasing the labor costs for the flashing replacement. |
| Interior Drywall Damage | If the leak has rotted the drywall inside the light tunnel over several years, the repair may require interior carpentry and painting alongside the exterior roofing work. |
Most standard residential skylights have a functional lifespan of about 15 to 20 years before the factory seals blow and the glass fogs up. If your skylight is 18 years old and the flashing is leaking, it is not cost-effective to pay a roofer $800 to re-flash a unit that will fail internally next year. Always opt to install a brand new, energy-efficient unit with new flashing kits concurrently.
Skylight Repair FAQs
Can you just seal the leak from the inside? expand_more
Do roofers fix the interior drywall damage? expand_more
How long does it take to replace a skylight? expand_more
What is a "tubular" skylight and do they leak? expand_more
Why is there dirt on the inside of my glass? expand_more
Do I need to replace the shingles around it? expand_more
Related Services & Coverage
Skylight flashing mechanics are very similar to chimney flashing repair, as both involve a large vertical penetration through the deck. If water has ruined the drywall surrounding the light shaft, review our ceiling water damage restoration protocols. Our LA roof leak repair dispatch connects properties in Studio City, Burbank, and the surrounding areas with verified experts equipped to handle advanced structural integrations.