Skylight Leaking: Repair It or Replace It?

The skylights that leak in Greater Victoria are mostly from one era. The 1980s and 90s homes of Broadmead, Dean Park and Brentwood Bay, and the family-room and kitchen additions of the same years across Saanich, were fitted with acrylic dome skylights on site-built curbs, often flashed with whatever the roofer had on the truck. Thirty years on, the acrylic has yellowed and crazed, the curb has weathered and the flashing has been sealed over at least once. On low-slope Gordon Head roofs the same units sit in torch-on, where a failed seam at the curb is the usual culprit.

Coastal humidity adds a false alarm. On a clear cold January morning a single-glazed unit runs with condensation that drips onto the sill and stains the drywall exactly like a leak. Under Douglas fir and cedar, needles pile up on the upslope side of the skylight and dam water against the flashing, which is why a skylight that never leaked can start after a few unswept seasons. Matching a replacement to the pitch and the roof material is part of a Victoria roofer's routine.

Before anyone climbs a ladder, check the weather pattern. Water that appears during or shortly after rain, on one side of the unit, is consistent with a leak. Water that appears on a cold clear morning on all sides, especially on an older acrylic or single-glazed skylight in a bathroom or kitchen, is consistent with condensation: warm moist air meeting cold glass. Condensation is a ventilation and glazing question, not a roofing repair, though it can still stain drywall and rot a wooden well over time.

Skylights are a hole in the roof with a box in it; the leak is almost always at the junction, not through the glass. A professional may inspect:

• The flashing kit on all four sides, and whether it is woven with the shingles or simply laid on top and sealed.
• The curb: a wooden frame the unit sits on, which rots if the flashing has been letting water in for years.
• The glazing seal between glass and frame, and the weep holes designed to drain small amounts of water.
• Debris damming water on the upslope side, common under conifers.
• On torch-on roofs, the membrane seam where it turns up the curb.

In our pricing model a skylight re-flash or reseal is $300 to $900 before GST, which fixes most flashing and seal problems on a unit that is otherwise sound. A full replacement, meaning a new unit and flashing kit installed as part of roofing work, is $1,500 to $3,000. The arithmetic turns on age: re-flashing a 25-year-old acrylic dome that is already yellowed and may have a soft curb costs a meaningful fraction of replacing it, and the replacement comes with new glazing, a proper flashing kit and a warranty.

If the roof is being replaced anyway, the shingles around the skylight come off regardless, so the incremental cost of a new unit is at its lowest.

The rule most local roofers apply is simple: if the roof is due within a few years, plan to replace the skylight at the same time and re-flash now only if it is actively leaking. If the roof is young and the skylight is under 10 years, a re-flash is the sensible fix. Either way, clear needles from above the unit each fall and have the flashing looked at when the roof is inspected.