Skylight Leaks in Bay Area Homes: How to Diagnose and Fix Them Before Winter

A skylight that drips during the first heavy rain of the season is rarely a defective skylight. In most Bay Area homes, the water comes from somewhere the skylight didn’t cause and the skylight is just the first place it shows up. This guide walks through how to diagnose the actual source, when a reseal is enough, when the flashing kit needs to be rebuilt, and how to think about timing with the rainy season getting closer.

Why Skylight Leaks Get Misdiagnosed

Homeowners almost always assume the skylight unit itself has failed. In the field, the unit is the cause maybe one time in five. The other four are some combination of step flashing that wasn’t installed to the manufacturer’s spec, deteriorated sealant at the curb, underlayment that was cut short during the original install, or condensation from poor attic ventilation collecting on the cold underside of the glass and dripping onto the drywall below.

Condensation in particular gets repaired as a leak over and over. The tell is timing: a true leak appears during or shortly after rain. Condensation appears on cold, clear mornings after a humid night inside the house, and stops the moment the sun warms the glass.

The Four Real Sources of Skylight Water Intrusion

• Step flashing failure: The L-shaped metal pieces woven into the shingles along the curb sides separate, lift, or corrode. This is the single most common true leak.
• Head and apron flashing: The top and bottom flashing pieces are where ice-dam-style water backup shows up first in Bay Area homes that get hit by wind-driven rain. Sealant alone never fixes this — the metal has to be re-set.
• Curb-to-glass seal: On older units, the gasket between the glass pane and the aluminum or wood curb dries out. Visible from the inside as water running down the glass itself, not the surrounding drywall.
• Underlayment cut short: A hidden install defect. The underlayment was trimmed at the skylight opening instead of being run up and onto the curb. No surface repair fixes this — the shingles around the unit have to come off.

How to Diagnose Without Tearing Anything Apart

Before any contractor opens up the roof, three quick checks narrow the source:

1. Hose test from the bottom up. Spray the wall below the skylight first, then the apron flashing, then each side, then the head, waiting a few minutes between zones. The leak appears in the same sequence as the spray.
2. Inspect the attic during the next storm. Trace the water back from the visible drip on the drywall to the underside of the decking. If the drip starts a foot above the skylight, the leak is in the field of the roof, not the skylight at all.
3. Check the curb interior for staining. Brown streaks running down the inside of the curb but a dry ceiling around it points to the gasket. Stains on the drywall but a dry curb interior points to flashing.

Reseal, Reflash, or Replace: What Each Repair Actually Means

The three paths sound similar and produce very different outcomes. A reputable contractor should explain which one your situation needs and why:

• Reseal: Replacing dried sealant at the curb-to-glass gasket. Appropriate only when the unit is structurally sound and the leak is at the glass interface. Buys time but never solves a flashing problem.
• Reflash: Removing the surrounding shingles, re-installing step flashing, head and apron flashing, ice-and-water membrane up the curb, then re-shingling. This is the correct repair for the majority of true skylight leaks. The skylight unit itself stays in place.
• Full replacement: Required when the curb is rotted, the glass seal has failed internally, or the unit is more than 20 years old and parts are no longer available. Often the right call if you’re already paying for the flashing work because the labor overlap is significant.

Our roof repair team handles all three approaches and will explain in writing which one fits the failure mode we find on your roof.

Timing: Why the Window Closes Fast

Bay Area atmospheric river season is typically heaviest from November through March. Reflashing work needs a forecast of at least 48 dry hours, and crews book out fast once the first storm of the season hits and every homeowner discovers the leak at the same time. Diagnostic work done now produces a parts list and a scheduled date. Diagnostic work done after the first storm produces a waiting list.

What to Ask Before Hiring

• Will you remove shingles to inspect the step flashing, or are you only resealing from the surface?
• Are you replacing the underlayment around the curb, or working over the existing layer?
• Is the new flashing kit the manufacturer’s part for my specific skylight model?
• What is the warranty on the repair, and does it cover the surrounding shingles if water tracks past the new flashing?
• Is the work covered under your CSLB Class C-39 license, and can I see the certificate of insurance?

Frequently Asked Questions

Can a skylight leak be fixed without removing shingles?

Surface sealant repairs sometimes hold for a season but rarely solve a true flashing failure. The water path runs underneath the shingles, so the only repair that addresses the cause requires lifting shingles to access the step and head flashing. A contractor who promises a permanent fix without touching the surrounding roof is selling a temporary patch.

How do I tell the difference between a skylight leak and condensation?

Condensation appears on the underside of the glass on cold mornings after humid nights inside the house. A leak appears during or shortly after rain. If the moisture pattern follows weather, it’s a leak. If it follows humidity, it’s a ventilation problem and the skylight is a victim, not the cause.

How long does a skylight reflash take?

A single skylight reflash, with the unit staying in place, is typically completed in one day. Full replacement adds a half day for curb work and interior trim. Permit inspection, when required, can add scheduling time but not crew time.

Does homeowner’s insurance cover a skylight leak in California?

Sudden damage from a storm event, falling debris, or impact is generally covered. Gradual leaks from worn sealant or end-of-life flashing are excluded as maintenance. If a storm damaged the unit, document with photos before any repair and ask the contractor for a written cause-of-loss statement that ties the damage to the event.

Should I replace my skylight when I replace the roof?

Almost always yes. The labor to integrate new flashing into an existing skylight curb is significant, and a 15-year-old skylight under a brand-new 30-year roof is the most common cause of premature post-replacement leaks. Replacing both at once is the only way the warranties align cleanly.

What’s the lifespan of a skylight in a Bay Area home?

Quality units last 20 to 25 years before the seals begin to fail. Sun-exposed south and west elevations age faster. If your home was built in the early 2000s or before and still has the original units, plan for replacement as part of the next roof cycle rather than reacting to the first leak.