Short answerA leaking skylight is usually not the glass. Most of the time the water comes in where the skylight meets the roof: the flashing and the curb. Sometimes it is not a leak at all, but condensation. Finding which one it is decides the fix.
Where do skylights leak?
At the flashing around the curb, at a cracked or crazed plastic lens, or at a failed seal between the lens and the frame.
Old plastic domes get brittle and crack in years of desert sun. Flashing gets lifted by wind or was never tied into the underlayment properly. On a tile roof, the tile around the skylight has to be lifted to see the flashing, the same way it is around a chimney.
Is it a leak or condensation?
If the drips show up on cold mornings with no rain, it is likely condensation. If they show up during or after rain, it is a leak.
Condensation is fixed with ventilation and insulation, not with sealant.
What skylights are allowed in a fire zone?
In unincorporated LA County fire hazard severity zones, skylights must be multi-pane with at least one tempered pane, or glass block, or rated for at least 20 minutes.
That covers Acton, Agua Dulce, Leona Valley and the other county towns where a home is mapped in a zone. A single-pane plastic dome does not meet it, so a replacement there has to.
Sources: LA County Building and Safety, Fire Hazard Severity Zone Construction Notes. Checked October 18, 2026.
Repair or replace the skylight?
Reflash and reseal when the unit is sound; replace when the lens is cracked, the frame has failed or the unit is too old to seal.
See skylight repair and skylight installation for what each job includes.