Why does my skylight leak when it snows?
Snow and ice press against the curb and the flashing, and meltwater collects on the up-slope side. If the flashing or sealant has any gap, that water finds it. A skylight set on a low pitch or at an eave where ice builds is most at risk, and the leak often only shows during a thaw.
Ice can lift the edge of flashing and shingles. The fix is usually a better flashing detail, sometimes with a small cricket on the up-slope side to shed water around the unit.
If ice dams also form at the eave below, the attic may need work. See ice dam removal and prevention.
How can I tell condensation from a leak?
Condensation forms on cold glass or the frame when warm, humid indoor air meets them, and it appears in winter on clear days as well as wet ones. A leak shows with rain or thaw and leaves stains on the shaft or ceiling. Droplets between panes mean the glazing seal has failed.
Better ventilation and a warm glass surface cut condensation. A leak needs the roofer.
Should I repair or replace an old skylight?
Repair when the unit is sound and the flashing has failed. Replace when the glazing is fogged, the frame is rotted, parts are unavailable, or the unit has leaked repeatedly. Replacing during a re-roof is often wise because the flashing can be done properly with the shingles off.
Ask for both prices in writing. A skylight that is tied into a new roof is flashed as part of one system and tends to last longer.
Who does the interior repair?
A roofer fixes the leak, not the ceiling. Wet drywall, insulation and paint belong to other trades and are done once the roof is dry. A good roofer says what damage they see inside, so you can plan, and photographs it for your records.
Allow time for the shaft to dry before finishing. Sealing damp drywall invites mould.
What should I do about a leaking skylight until the roofer comes?
Contain the water inside with a bucket and towels, move belongings away, and leave the skylight alone. Do not climb up to caulk it in wet or cold weather. A roofer can cover the unit temporarily if conditions allow. A skylight leak is usually a flashing issue, so a patch of sealant seldom lasts.
If the shaft is dripping, a sheet of plastic taped under the light well can guide water into a container. Check the ceiling and the shaft walls for bulging, and keep people out from beneath any sagging area.
Photograph the stains and note when the leak happens. A leak only in the thaw points to snow and ice at the curb, while a leak in every rain points to the flashing or the glazing. That detail shortens the roofer's search and helps decide between a repair and a replacement.
