Skylight Leaks in Arizona: Causes, Fixes and When to Replace the Skylight

2026-10-04 · 8 min read

A skylight is a hole in your roof with a window in it, and in the Valley it takes the full force of sun, heat and monsoon rain. When one leaks, the cause is usually the flashing or curb around it, not the glass. This guide explains how skylights fail in Arizona, how to find the real source and what the fix involves.

Why skylights are a common leak point

Every roof penetration interrupts the waterproofing, and a skylight is the largest one most homes have. Water running down the roof hits the uphill side of the skylight and has to be steered around it. Wind-driven monsoon rain pushes water sideways and upward against the frame. Then the sun bakes the sealants and plastic parts every summer afternoon.

In Phoenix, roof surfaces commonly reach 150 to 170°F on summer days and cool sharply after dark. The skylight frame, the curb, the flashing and the roofing all expand and contract at different rates. Over years, that movement opens joints and cracks sealant.

Most skylight leaks show up during the monsoon, which runs from June 15 to September 30, because that is when Valley roofs get heavy, wind-driven rain after months of dry heat.

Leak or condensation? Check this first

Not every drip under a skylight is a roof leak. Condensation forms when warm, humid indoor air meets a cold skylight surface. In the Valley this is most common on winter mornings, and in bathrooms and kitchens where steam rises into the skylight well.

Signs it is condensation:

Water appears on cool mornings, not during or after rain.
Droplets cover the inside of the glass or dome evenly.
The skylight is over a shower, bath or cooktop.
The drywall in the well is damp all around, not stained on one side.

Signs it is a leak:

Water appears during or right after rain, especially wind-driven rain.
Stains are on one side of the skylight well, often the uphill side.
Stains grow after each storm.
Water drips from the frame or the drywall, not from the glass.

Condensation is fixed with better ventilation, such as running a bath fan, or by replacing an old single-pane unit with an insulated one. Leaks are fixed on the roof.

How skylights fail in the Valley

These are the usual causes:

Flashing problems. The metal or flashing kit around the skylight is missing, installed in the wrong order, rusted or bent. On tile roofs, the flashing has to work with the tile profile, and poorly integrated flashing is a frequent leak source.
Sealant used instead of flashing. Many skylights depend on caulk or roof cement that dries and cracks in the sun within a few summers.
Debris on the uphill side. Leaves, dust and broken tile collect above the skylight, dam water and push it over the flashing. A cricket or diverter on wide skylights helps.
A failed curb. Wood curbs can rot from slow leaks, and short curbs on low-slope roofs let ponding water reach the top of the curb.
Old plastic domes. Acrylic and polycarbonate domes yellow, become brittle and crack after long UV exposure. Hail can crack them too.
Failed glazing seals. Insulated glass units lose their seals with age, which fogs the glass and can let water in at the frame.
Aging underlayment around the skylight. On tile roofs, the felt around the curb ages like the rest of the roof, and the skylight is often where it shows first.

What building code says about skylight curbs

The International Residential Code, which Valley cities adopt with their own amendments, requires unit skylights on roofs flatter than 3 inches of rise per 12 inches of run to be mounted on a curb at least 4 inches above the plane of the roof, unless the skylight manufacturer's instructions say otherwise. On steeper roofs, curbs are not required by that section.

This matters in the Valley because so many homes have low-slope sections, flat roofs over additions, patio rooms and Pueblo-style designs. A skylight set nearly flush with a flat roof surface will see standing water reach its edges in a heavy storm. Raising it on a proper curb and flashing that curb into the roofing is often the permanent fix for a skylight that leaks on a flat roof.

Skylight leaks on tile, shingle and flat roofs

Tile roofs. The skylight sits below the tile surface, so water that runs under the tile must be carried around the curb by the underlayment and flashing. A proper detail includes a head flashing at the top, side flashings that tie into the tile pans and an apron at the bottom that lets water drain over the tile below. Fixing a tile roof skylight leak means lifting tile around the skylight, replacing the underlayment and flashing around the curb and relaying the tile.

Shingle roofs. Skylights are typically installed with a manufacturer flashing kit or step flashing woven into each shingle course along the sides, with a head flashing and a sill apron. Leaks usually come from missing step flashing, a face-nailed or caulked repair, or shingles that have aged around the skylight.

Foam and flat roofs. The curb is foamed and coated into the roof surface. Leaks come from coating that has cracked where it meets the curb, a curb that is too short for the water level in a storm, or a curb top that isn't sealed. Repairs involve cleaning, rebuilding foam or membrane at the curb and recoating.

Repair the skylight or replace it?

Repair makes sense when the skylight unit itself is in good shape and the problem is the flashing, sealant, curb height or surrounding roof. Re-flashing a sound skylight is usually a smaller job than replacing it.

Replacement makes sense when:

The dome is yellowed, brittle, crazed or cracked.
The insulated glass is fogged or its seal has failed.
The frame is warped or corroded.
The curb is rotted and has to be rebuilt anyway.
You are already replacing the roof or the tile underlayment, so the skylight area is fully open.

The last point is worth weighing carefully. During a re-roof or underlayment replacement, the skylight's flashing is replaced anyway. If the skylight is old, replacing it at the same time costs less than coming back later and opening the new roof.

Removing a skylight altogether is also an option. The opening is framed in, decked over and roofed. That work involves the roof framing, so it needs an appropriately licensed contractor and may need a permit.

Who can replace a skylight, and permits

Under Arizona Registrar of Contractors rules, a licensed roofing contractor may install new or replace existing skylights where the work does not require changes to the roof framing or structure. Enlarging an opening, cutting rafters or adding a skylight where none existed usually involves framing and requires the appropriate license.

Permit rules vary by city. Surprise, for example, exempts replacing skylights or tubular daylighting devices without altering rafters from a building permit. Other cities treat it differently, and new openings in a roof generally need a permit. Check with your city's building department before work starts, and check your HOA's guidelines if the skylight's size or appearance will change.

Tubular skylights and solar tubes

Tubular daylighting devices, often called solar tubes, use a small dome on the roof and a reflective tube down to a ceiling diffuser. They are popular in Valley homes because the roof opening is small and they let in less heat than a large skylight.

They still leak for the same reasons: flashing installed incorrectly, especially on tile roofs where the flashing has to fit the tile profile, sealant used in place of proper flashing, or a cracked dome. Condensation inside the tube is also common in winter. Repairs follow the same approach as a skylight: fix the flashing and underlayment around the opening, replace a cracked dome, and on tile, make sure the flashing is designed for tile.

What to do now

If your skylight is leaking:

Protect the floor and furniture under it and take photos of the stains with dates.
Note when it leaks: during wind-driven rain, any rain, or on cold mornings.
Look at the roof from the ground or with binoculars for debris above the skylight, cracked tile or a yellowed dome. Don't climb on a tile roof.
Avoid smearing roof cement around the skylight. It may slow the leak for a season, but it makes the proper repair harder.

Our standard roof inspection is free. We check the skylight flashing, curb, dome and the roofing and underlayment around it, and we give you photos and a written scope that says whether the skylight can be re-flashed or should be replaced. Repairs usually fall within our typical repair range of $300 to $5,000, depending on roof type, height and what has to be rebuilt.

Frequently Asked Questions

Why does my skylight only leak during monsoon storms?

Monsoon storms bring wind-driven rain that pushes water sideways and up against the skylight frame, along with heavy bursts that overwhelm worn flashing or short curbs. A skylight that stays dry in a gentle winter rain can leak in those conditions. The usual causes are flashing problems, cracked sealant, debris damming the uphill side or a curb too low for a flat roof.

How do I know if my skylight is leaking or just has condensation?

Condensation appears on cool mornings, often over bathrooms or kitchens, and beads evenly across the inside of the glass or dome. A leak appears during or after rain, stains one side of the skylight well, often the uphill side, and grows after each storm. Condensation is fixed with ventilation or an insulated unit; a leak is fixed on the roof.

Can a leaking skylight be fixed without replacing it?

Often, yes. If the dome or glass and the frame are in good condition, the fix is usually new flashing, a rebuilt or raised curb, or new underlayment around the opening. Replacement makes more sense when the dome is yellowed or cracked, the glass is fogged, the frame is damaged, or you are already replacing the roof around it.

Does a skylight on a flat roof need a curb?

Under the International Residential Code, unit skylights on roofs with less than 3 inches of rise per 12 inches of run must be mounted on a curb at least 4 inches above the roof surface, unless the manufacturer's instructions say otherwise. Valley cities adopt the code with local amendments, so check your city's version. A proper curb keeps storm water away from the skylight's edges.

Should I replace my skylight when I replace my roof?

If the skylight is older, usually yes. Its flashing is replaced during the re-roof anyway, and the area around it is fully open. Replacing an aging skylight then costs less than reopening a new roof later to replace it. If the skylight is newer and in good condition, it can be re-flashed into the new roof instead.

Can a roofer replace a skylight in Arizona?

Yes, within limits. Arizona ROC rules let licensed roofing contractors install or replace skylights where the work doesn't require changes to the roof framing or structure. Enlarging an opening or cutting rafters for a new skylight involves framing and needs the appropriate license. Permit requirements vary by city, so check with your building department.