Water at the light well can come through the skylight unit, its flashing, the curb, nearby shingles or membrane, an upslope roof detail, or condensation on the interior surface. The stain may also sit below where water first entered because moisture can travel along underlayment, decking, framing, and insulation. We begin with when the water appears, which side gets wet, whether the symptom follows rain, wind, thaw, snowmelt, or indoor humidity, and whether previous sealing or roofing work changed the pattern. That history keeps the first repair from becoming a guess based only on the ceiling mark.
A skylight is a deliberate opening in the roof, so its flashing has to collect and shed water back onto the roofing surface. On a shingle roof, that can involve sill, side or step, and head-flashing details integrated in the correct sequence with the shingles and underlayment. Flat and low-slope roofs usually rely on a curb and a compatible membrane transition. VELUX Canada publishes different flashing instructions for shingles, shakes, tile, metal, low-slope, curb-mounted, and deck-mounted applications. The existing skylight model and roof type therefore matter more than adding another bead of sealant around the frame.
A cracked shingle, open seam, wall transition, valley, vent, or ice-related detail above the skylight can send water toward the opening and make sound skylight flashing look responsible. Debris can also slow drainage around the head and side flashing. We inspect the surrounding field, upslope transitions, fasteners, prior patches, and the path water is expected to follow. On a flat roof, ponding, membrane condition, parapets, nearby curbs, and drains may be part of the same investigation. The repair scope should identify the observed failure area and any neighbouring condition that could continue feeding it.
Interior moisture on glass during cold weather can run down the frame or light well and resemble a roof leak. Tarion’s construction performance guidance notes that skylight condensation can occur when indoor relative humidity is high and treats it separately from water penetration. Timing, visible droplets, staining pattern, bathroom or kitchen moisture, indoor humidity, air leakage, insulation around the shaft, and ventilation clues help separate the possibilities. Roofing work will not correct an indoor humidity or shaft-insulation problem, so we flag evidence that should be reviewed by the appropriate insulation, ventilation, or skylight professional.
A localized roofing or flashing defect may support a targeted repair when the skylight, curb, deck, and surrounding roof remain serviceable. Repeated sealant patches, corroded or incomplete flashing, a deteriorated curb, damaged cladding, failed glazing seals, cracked domes, rot, or an older unit near a planned roof replacement can change the economics. We separate work Ridgeborn can perform at the roof tie-in from glazing, hardware, electrical blind, or manufacturer-specific service that may belong with the skylight maker or another specialist. If replacement is the better path, the opening, mounting type, roof material, pitch, and structural condition need to be confirmed before ordering.
Move valuables away from the opening, collect drips where it is safe, and keep people clear of bulging drywall, wet electrical fixtures, or falling material. Do not climb onto a wet, icy, steep, or snow-covered roof. Weather, daylight, pitch, access, and the repair material determine whether a crew can inspect safely, install temporary protection, or complete permanent work. A temporary measure can reduce exposure until a suitable weather window, but it should be documented and followed by the repair or replacement decision rather than treated as a finished skylight detail.
A leak repair around an existing opening is different from cutting a new skylight into a roof or changing structural framing. The City of Toronto lists some skylight installations in houses and small buildings as work that may not require a building permit when the stated structural limits are met, while material structural alterations can require one. Ridgeborn does not assume the permit answer from the word “skylight.” If the scope changes the opening, rafters, joists, trusses, curb, or another structural component, the owner should confirm the project with Toronto Building and involve the appropriate designer or structural professional before work proceeds.
A useful scope identifies the reported symptom, accessible interior or attic findings, roof and skylight details reviewed, suspected or confirmed failure, proposed work, access assumptions, and any limitation that prevented a conclusion. After repair, keep photographs and the work description with the roof records, then monitor the area through the next relevant rain, wind, thaw, or cold-weather condition. If moisture returns, the documented pattern helps distinguish a missed water path from condensation or a separate defect instead of restarting with no history.
