A leaking commercial skylight is almost never a failed glazing panel. It is a failed curb-to-membrane integration or a compromised perimeter flashing. We find the failure source and fix it at the roof system level - not the window-caulk level.
Commercial skylights in Raleigh office buildings, retail centers, and institutional facilities are persistent leak sources - not because the glazing fails, but because the interface between the skylight curb and the surrounding roof membrane deteriorates over time in ways that a visual check from below does not reveal. By the time water stains appear on the interior, the failure has typically been working against the curb flashing or the membrane-to-curb transition for months.
We see skylight leak complaints regularly on North Hills mixed-use buildings, Downtown Raleigh office towers with atrium skylights, and institutional buildings on Raleigh campus's Centennial Campus where daylighting strategies have resulted in complex skylight configurations. The failure pattern is consistent: the membrane's vertical leg at the curb has separated or the coping cap at the top of the curb has allowed water behind it, and the leak path runs down the curb face and through whatever gap exists at the curb base.
Repairing a skylight leak correctly means treating the curb as a large penetration - which it is - and integrating the roof membrane system around it the same way we would any other elevated curb on the roof. That means a full-height base flashing, a continuous weld or bond to the field membrane, and a properly sealed coping or cap at the top of the curb. Caulking the bottom corner and hoping for the best is not a repair; it is a delay.
Diagnosing the Skylight Leak Source
Skylight leaks on commercial buildings have four primary sources, and distinguishing between them before starting work matters enormously. Source one: the membrane base flashing at the curb base has separated or failed - water enters at the curb-membrane transition and runs down the inside of the curb. Source two: the coping or cap at the top of the curb has failed or the glazing frame seal has deteriorated - water enters at the top and runs down the face of the curb or the frame interior. Source three: condensation from the interior - not a roof leak, but the visual symptom inside is identical. Source four: a membrane failure in the field area adjacent to the curb, with water traveling along the deck to the curb.
We test each hypothesis systematically before committing to a repair scope. A water test - controlled application of water to specific curb surfaces and perimeter zones while someone monitors the interior - is often the fastest way to confirm the source on a commercial skylight. Infrared scanning of the insulation around the curb identifies moisture accumulation in the adjacent insulation assembly, which helps confirm whether the field membrane or the curb flashing is the primary failure.
Condensation misidentified as a leak is a genuine issue on commercial skylights in the Triangle's climate. Raleigh's summer humidity is high enough that interior-facing glazing surfaces on skylights can produce visible condensation that runs down the frame and drips into the space below, particularly on older single-pane or poorly-framed commercial skylights. We confirm whether the water source is exterior infiltration or interior condensation before proceeding with any exterior repair work.
Curb Flashing Repair and Re-Integration
The skylight curb base flashing is the most common repair we perform on Raleigh commercial skylights. On TPO and EPDM membrane systems, the curb base flashing is a heat-welded or bonded vertical membrane leg that runs from the field membrane up the curb face to a termination point at or near the top of the curb. When this flashing separates at the field weld or the termination bar, water enters at the gap.
Repair procedure: remove all existing failed flashing and any prior patch material from the curb face; prepare the membrane surface and curb surface per manufacturer specification; install new base flashing material - the same membrane type as the field - welded to the field membrane at the base and mechanically anchored at the top; install a continuous termination bar with compatible caulk at the termination line. On curbs where the substrate - typically wood or metal - has deteriorated, we address the substrate before installing new flashing.
Counter-flashing at the top of the curb - the metal cap or coping that protects the termination of the base flashing - is re-installed with sealed lap joints and mechanically anchored ends. We specify counter-flashing materials that are compatible with the frame material to avoid galvanic corrosion between dissimilar metals, which is a long-term failure mechanism on commercial skylights in the Triangle's moisture environment.
Glazing and Frame Seal Repair
When the confirmed leak source is the glazing perimeter seal rather than the base flashing - an interior-to-exterior water path through the glazing frame - the repair involves resealing the glazing unit within its frame. On commercial skylights with aluminum frames, the glazing tape and sealant at the glass-to-frame joint ages out over time, particularly under the Triangle's UV exposure. The original sealant on a 20-year-old commercial skylight in Raleigh is likely well past its design service life.
Glazing seal replacement requires removing the glazing hold-down caps, removing the old seal material completely, cleaning the frame and glass edge, and re-installing new glazing tape and sealant per the manufacturer's current specification. We do not apply new sealant over old sealant - that creates a layered joint that fails faster than a clean installation because the bond between the layers is weaker than either layer's bond to the substrate.
Polycarbonate and acrylic dome skylights - common on lower-cost commercial construction in the Raleigh market and on older retail buildings in the Crossroads and North Hills commercial corridors - have additional failure modes: UV yellowing that reduces light transmission, stress cracking from thermal cycling, and snap-fit attachment failures at the dome flange. We assess dome condition and advise on repair versus replacement based on current dome transparency, structural integrity, and the cost comparison between dome replacement and full skylight unit replacement.
Frequently asked questions
Can you repair a commercial skylight that is still under the roof's manufacturer warranty?
Yes, with attention to warranty compliance. The roof membrane system around the skylight curb is typically covered under the roof manufacturer warranty. Repairs to the base flashing must use manufacturer-approved materials and follow manufacturer repair protocols to preserve warranty coverage on the surrounding field. We identify active warranty status before beginning any skylight flashing work and coordinate with the manufacturer's warranty service when the repair scope is significant enough to require manufacturer awareness.
Our skylight leaks only during heavy rain with wind - not during lighter rain. What does that tell you?
Wind-driven rain leaks typically point to the upper portion of the curb assembly - the coping cap, counter-flashing termination, or glazing frame seal - rather than the base flashing, which fails under water ponding pressure. Wind pushes water up and behind surfaces that shed water under gravity-only conditions. The wind-driven pattern also suggests the leak path is at or near the top of the curb rather than at the curb base. We use that diagnostic clue to direct the inspection to the most likely source locations before testing.
Is it worth repairing an old commercial skylight or should we consider replacing it?
Repair makes sense when the curb structure is sound, the glazing has acceptable light transmission and structural integrity, and the repair cost is significantly less than replacement. Replacement makes sense when the curb has rotted or corroded substrate, the glazing is UV-degraded beyond acceptable performance, the skylight design is no longer compliant with current energy code, or the building program has changed in a way that makes the skylight location a liability rather than an asset. We assess and tell you honestly which situation you are in - we do not have a financial preference for repair over replacement or vice versa.
