Skylight Leak: Causes, Fixes and When to Replace

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A water stain spreading across the drywall around a skylight is one of the more frustrating things to find after a storm. Skylights bring daylight deep into a room, but they also put a hole in the roof, and every hole in a roof depends on flashing, seals and careful installation to stay dry. A skylight leak can come from the flashing, the glazing seal, the curb, the surrounding shingles, ice dams, or even condensation that is not a leak at all. This guide explains the common causes, how to tell condensation from a true leak, temporary fixes, when to repair versus reflash versus replace, how the decision ties to roof replacement timing, Colorado hail concerns, and typical costs. Costs are general 2026 estimates and vary by roof type, skylight size and contractor.

Part of our Structure & Exterior guide — start there for the full picture →

Why Skylights Leak: The Short Answer

Most skylight leaks trace back to the flashing, the metal and membrane system that sheds water around the skylight where it meets the roof. Failed or poorly installed flashing lets water run behind the skylight frame and into the ceiling. The next most common causes are a failed seal between the glass and frame, damage to the skylight itself, and ice dams that back water up under shingles. Condensation on the inside of the glass is also frequently mistaken for a leak.

The right fix depends on the cause. A failed seal on a newer unit might be a small repair. Flashing problems usually mean removing shingles around the skylight and reflashing. An old, cracked or hail-damaged unit generally calls for replacement, ideally timed with a roof replacement if the roof is near the end of its life.

Common Causes of a Skylight Leak

Failed or Improper Flashing

Skylight flashing typically includes a head flashing at the top, step flashing along the sides that interleaves with each course of shingles, and an apron flashing at the bottom. Underlayment and self-adhered membrane add a second layer of protection. Leaks happen when:

• The original installer relied on roofing cement or caulk instead of a proper flashing kit.
• Step flashing was skipped or installed in the wrong order.
• Flashing was reused from an old installation during a reroof and no longer fits.
• Shingles or nails near the flashing were damaged or disturbed.
• Sealants have dried, cracked and pulled away over years of sun and temperature swings.

Colorado’s intense high-altitude sun and large daily temperature swings are hard on sealants, so caulk-dependent installations can fail sooner than homeowners expect.

Failed Glazing Seal or Cracked Glass

The seal between the glass or acrylic and the skylight frame can degrade. On insulated glass units, a failed seal often shows up first as fog or haze trapped between the panes. If the outer seal has failed, water can enter at the glazing and drip into the frame. Cracked glass or a split acrylic dome is an obvious entry point.

Ice Dams and Snow Load

In winter, heat escaping into the attic melts snow on the roof, and the meltwater refreezes at colder areas, including around skylights. A skylight on a low-slope section or below a larger roof plane can collect snow and ice on its uphill side, and the backed-up water can work under shingles and flashing. Heavy snow can also stress older domes and frames. ENERGY STAR notes that attic air sealing combined with insulation can help alleviate the formation of ice dams. Our ice dams guide covers prevention in more detail.

Poor Original Installation

Skylights installed without a manufacturer’s flashing kit, without a proper curb, or with the wrong slope rating are prone to leaks. Some skylights are rated for a minimum and maximum roof pitch; installing one outside that range can trap water. A poorly framed light shaft can also leave gaps where warm, moist indoor air reaches cold surfaces.

Aged Curb-Mounted Units

Many older homes have curb-mounted skylights, where the unit sits on a raised wooden box (the curb) built on the roof. Over decades, the curb’s wood can rot if water gets behind the flashing, the fasteners loosen, and older acrylic domes become brittle and yellow. When the curb itself has deteriorated, a simple seal repair rarely holds for long.

Leak or Condensation? How to Tell

Condensation forms when warm, humid indoor air meets the cold surface of the skylight glass. Water beads up and can drip onto the floor or run down the light shaft, looking very much like a leak. Bathrooms and kitchens with skylights are especially prone to it.

Clues that point to condensation:

• Water appears on cold mornings, often on clear, dry days with no rain or melting snow.
• Droplets cover the inside surface of the glass evenly.
• The problem is worse after showers, cooking or a humidifier running.
• It improves when indoor humidity drops or a bath fan runs longer.

Clues that point to a leak:

• Water appears during or shortly after rain, snowmelt or wind-driven storms.
• Stains are concentrated at one corner or along one side of the shaft.
• Drywall is soft or bubbling at the top of the light shaft.
• From the attic, water trails, dark wood or wet insulation appear around the skylight framing.

A simple test can help: on a dry day, have one person run a garden hose over the roof in sections, starting at the bottom of the skylight and working up, while another watches inside. Only do this if roof access is safe; on steep or high roofs, leave it to a roofer.

Reducing indoor humidity, running bath fans during and after showers, and keeping the shaft well insulated all help with condensation. Persistent condensation can lead to mold on the shaft and frame, which our guide to mold on windows from condensation covers.

Temporary Fixes Until a Repair

A temporary fix buys time but rarely solves the problem. Reasonable short-term steps include:

• Protect the interior. Put a bucket or tarp under drips, move furniture and electronics, and dry wet materials quickly.
• Clear debris and snow from around the skylight from the ground or a safe position, using a roof rake for snow, never climbing onto an icy roof.
• Apply a roofing sealant to an obvious gap at the flashing or a small crack in the frame, on a dry day, as a stopgap.
• Tarp the area if a dome is cracked or hail-damaged, extending the tarp up the roof so water does not run underneath it.
• Document the damage with photos and dates, especially if an insurance claim is possible.

Sealant patches often fail within a season because they treat symptoms, and smearing caulk over flashing can make a proper repair harder later. Plan for a real repair soon after any temporary fix.

Repair vs Reflash vs Replace

Repair

A repair makes sense when the skylight is relatively new and in good condition and the problem is localized, such as a damaged section of sealant, a loose fastener, or a single shingle or flashing piece that was disturbed. Some manufacturers sell replacement glazing or seal kits for specific models.

Reflash

Reflashing means removing shingles around the skylight, replacing underlayment and membrane, and installing a new flashing kit. It is the right fix when the skylight unit is sound but water is getting past the flashing. Reflashing an older skylight is sometimes false economy, since labor is a large part of the cost and the unit may need replacing a few years later anyway.

Replace

Replacement is usually the better choice when:

• The skylight is old, often cited as somewhere around 15 to 20 years or more, though lifespan varies by product and climate.
• The glazing seal has failed and the unit is fogged between panes.
• The dome is cracked, crazed, brittle or hail-damaged.
• The curb or frame is rotted.
• The roof is being replaced anyway.

Replacing also offers a chance to upgrade efficiency. ENERGY STAR certifies skylights and recommends choosing products certified for the local climate zone, with the label typically shown next to the NFRC label. Some homeowners decide to remove a skylight entirely and patch the roof deck, which eliminates the leak risk but loses the daylight.

Timing a Skylight With Roof Replacement

Skylight flashing is interwoven with the surrounding shingles, so reflashing or replacing a skylight disturbs the roof. If the roof is within a few years of replacement, it often makes sense to wait and do both together, using a temporary fix in the meantime. Roofers typically replace flashing kits during a reroof, and many recommend replacing older skylights at the same time because the incremental labor is lower and the warranty picture is cleaner.

Conversely, if a skylight was replaced recently and the roof is new, the work should be covered by the installer’s workmanship warranty, and a leak should go back to that contractor first. Our roof replacement cost guide covers how roof timing, hail claims and materials affect the budget.

Colorado Hail and Skylights

The Front Range is one of the more hail-prone regions in the country, and skylights are among the more vulnerable parts of a roof. Older plastic and acrylic domes, especially sun-aged ones, can crack or shatter in a strong hailstorm. Glass skylights with tempered or laminated glazing generally hold up better, though hail can still damage frames, flashing and the surrounding shingles.

After a hailstorm, look for cracks, crazing or punctures in domes, dents in metal flashing, and granule loss on shingles around the skylight. Damage may be covered under homeowners insurance as part of a hail claim, depending on the policy and deductible. Ask a contractor or adjuster to document skylight damage separately so it is not overlooked. When replacing, ask about impact-rated options.

Hail damage is not always visible from the ground. A small puncture or a hairline crack in an acrylic dome may not leak until the next heavy rain or snowmelt, weeks after the storm. Many policies set time limits for reporting storm damage, so a prompt roof check after a significant hail event is worth scheduling even if nothing is dripping yet.

Interior Damage and Mold Risk

Even a slow skylight leak can soak drywall, insulation and framing in the light shaft and the attic around it. Insulation can hold water out of sight, and wet framing can stay damp long after the rain stops. EPA guidance emphasizes that the key to mold control is moisture control and that water-damaged areas and items should be dried within 24 to 48 hours to prevent mold growth.

After a leak is fixed:

• Check the attic around the skylight for wet insulation, stained sheathing and rafters.
• Replace insulation that stayed wet; it may not dry well in place.
• Watch for recurring stains, soft drywall or a musty smell in the room.
• Clean small areas of mold following EPA guidance, and get professional help for larger areas.

Our guide to visible mold explains what to look for and when testing or professional remediation makes sense.

Preventing Future Skylight Leaks

Skylights do not need much attention, but a little routine care catches problems while they are still small.

• Look up after major storms. From the ground with binoculars, check domes for cracks and flashing for lifted edges, especially after hail or high winds.
• Check the ceiling twice a year. Faint stains, hairline cracks or peeling paint at the top corners of the light shaft are early warnings.
• Peek into the attic around the skylight framing in spring and fall for dark wood, water trails or compressed insulation.
• Keep the area clear. Pine needles, leaves and debris collect on the uphill side of a skylight and hold moisture against the flashing.
• Manage snow. Use a roof rake from the ground to pull heavy snow off lower roof edges, and address the attic heat loss that drives ice dams.
• Control indoor humidity in bathrooms and kitchens with skylights by running exhaust fans long enough to clear moisture.
• Mind venting skylights. Operable units have motors, rain sensors and weatherstripping that wear. Close them before storms and confirm the rain sensor still works.

Attic conditions matter, too. A well-sealed, well-insulated and properly ventilated attic keeps the roof deck colder in winter and reduces ice buildup around skylights. Our attic ventilation guide covers intake and exhaust balance.

Tubular Skylights

Tubular daylighting devices, sometimes called sun tunnels or light tubes, use a small rooftop dome and a reflective tube to bring light into a hallway or bathroom. They have a smaller roof opening and usually come with an integrated flashing, which can make them less leak-prone than a large framed skylight, but they can still leak at the flashing or through a cracked dome. Condensation inside the tube is also common when the tube passes through a cold attic without insulation, and it can drip from the ceiling diffuser in a way that looks like a roof leak.

Skylight Leak Repair Costs

Typical 2026 ranges, which vary widely by roof type, skylight size, pitch and access:

• Minor seal or flashing repair: commonly around $200 to $600.
• Reflashing an existing skylight: commonly about $500 to $1,500.
• Replacing a standard fixed skylight: commonly about $1,000 to $3,000 installed, more for venting or larger units.
• Replacing during a roof replacement: often less in added labor than a standalone replacement.
• Interior drywall and paint repair: commonly a few hundred dollars for a small area, more if the shaft or ceiling must be rebuilt.
• Removing a skylight and patching the roof: commonly about $500 to $1,500 plus interior finishing.

When to Call a Roofer or Inspector

A roofer or skylight installer is the right call for flashing work, unit replacement and any roof access. For a broader look at roof-related water problems, our roof leak guide covers how to trace leaks that are not coming from the skylight. Buyers should ask their inspector to look closely at skylights, the ceiling and the attic around them, and to note signs of past leaks or recent cosmetic patching. Our guide to hiring a home inspector explains what a typical inspection covers.

References

• A Brief Guide to Mold, Moisture and Your Home — U.S. Environmental Protection Agency
• Mold Cleanup in Your Home — U.S. Environmental Protection Agency
• Residential Windows, Doors and Skylights — ENERGY STAR
• Attic Air Sealing Project — ENERGY STAR

Found stains around a skylight in a home you are buying or selling? Send us a note and we can connect you with a Front Range inspector who can check the skylight, the attic around it and the roof before the leak becomes a bigger repair.