Skylights introduce magnificent natural sunlight into dark interior living rooms and kitchens. However, cutting a 4x4-foot opening in your roofline creates a primary water obstacle. When water pools against a raised curb, a failing seal or deteriorated metal flashing results in an active skylight leak that damages interior drywall tunnels.
The Anatomy of a Residential Skylight
Understanding the three main components of a skylight assembly helps pinpoint the source of water intrusion:
- The Insulated Glass Unit (IGU): Double-pane tempered or laminated glass sealed with argon gas. If the perimeter silicone seal fails, moisture enters between the panes, creating permanent foggy condensation.
- The Raised Wooden Curb: A framed 2x4 or 2x6 timber box rising 4 to 6 inches above the roof deck that elevates the skylight above water runoff.
- The Flashing Kit: Pre-formed aluminum or copper pieces—including a bottom sill apron, side step flashing pieces, and an upper saddle header—that channel water around the curb.
| Leak Symptom | Probable Cause | Recommended Repair |
|---|---|---|
| Water dripping down drywall shaft during rain | Corroded or improperly overlapped step flashing | Strip surrounding shingles, install self-adhering membrane and new flashing kit |
| Foggy moisture droplets trapped between glass panes | Insulated glass unit perimeter seal failure | Replace skylight sash or complete unit (Flashing may be reused) |
| Water pooling at lower corners of skylight frame | Clogged internal condensation weep holes | Clear weep channels with nylon brush and clean aluminum frame |
| Drywall peeling along upper ceiling curb | Missing or improper head flashing / back-pan | Install custom saddle flashing that directs water around the top curb |
Vapor Barriers & Interior Condensation Management
During cold winter evenings, humid air generated by cooking, hot showers, and laundry rises into high ceiling skylight shafts. Without proper insulation around the drywall light shaft, this warm indoor moisture strikes the cold skylight glass and aluminum frame, condensing into heavy water droplets that run down the drywall corners. Homeowners often mistake this winter condensation for a roofing leak.
To permanently solve condensation issues, contractors install continuous closed-cell spray foam or rigid R-15 polyiso board insulation tightly sealed against the exterior of the drywall shaft framing, and verify that the skylight unit incorporates built-in interior condensation collection gutters and exterior weeping ports.
Installing high-performance low-emissivity (Low-E) argon gas-filled skylights dramatically cuts winter thermal bridging, preventing condensation while blocking 99% of harmful ultraviolet rays that fade indoor furniture and hardwood flooring.
The Myth of "Caulking the Skylight"
Never attempt to stop a skylight leak by running silicone caulk around the glass frame or roof shingles. Water almost always enters 2 feet higher up on the roof along the head flashing. Surface caulk simply traps trapped water inside the wooden curb, accelerating dry rot of the framing timbers. Proper repair demands removing perimeter shingles, inspecting the wooden curb, and installing engineered flashing kits.
The Proper Flashing Kit Replacement Protocol
Durable skylight repairs require a complete flashing overhaul. Technicians remove shingles 24 inches around the perimeter, install self-adhering ice-and-water barrier extending 4 inches up the vertical curb sides, install interlocking aluminum step flashing cards, and nail replacement shingles into place. Learn more on our roof leak repair services and residential roof repair solutions.