Skylight Leak Repair: Why Coastal Home Skylights Fail and What to Fix (2026)

Why Skylights Leak: The 6 Root Causes

Every skylight leak I have diagnosed on the Grand Strand traces back to one of these six failure modes. Understanding which one is causing your leak determines whether you need a $200 reseal or a $2,500 replacement.

1. Flashing Failure — The Number One Cause

Flashing is the metal system that bridges the gap between the skylight frame and the surrounding roof surface. It consists of step flashing along the sides, a head flashing (also called a cricket or diverter) at the top, and an apron flashing at the bottom. Together, these pieces channel water around the skylight and back onto the roofing material below.

Flashing failure accounts for roughly 70 percent of all skylight leaks. The failure modes include corrosion of the metal itself, separation of flashing joints, sealant failure between the flashing and the skylight frame, and improper integration with the surrounding roofing material. In coastal areas, the combination of salt air corrosion and thermal movement accelerates every one of these failure modes.

The critical detail most homeowners miss is that flashing is a system, not a single piece. If one component fails — say the head flashing separates from the frame — water enters at that point and runs down behind the side flashing, making it look like the entire flashing system has failed. In reality, repairing one joint or replacing one piece can solve the problem completely.

2. Seal Deterioration

Every skylight has rubber gaskets and sealant between the glass and the frame, and between the frame and the curb. These seals are the second most common failure point. Rubber gaskets dry out and lose elasticity over time. Sealant cracks, shrinks, and pulls away from the surfaces it is bonded to. Both conditions create pathways for water.

In coastal South Carolina, UV exposure accelerates seal degradation significantly. The rubber gaskets on a skylight facing south or west — receiving maximum sun exposure — can begin hardening and cracking within 8 to 10 years. The same gaskets on a north-facing skylight may last 15 years. This is why two skylights on the same house can have completely different leak timelines.

3. Condensation Misdiagnosed as a Leak

Not every drip from a skylight is a roof leak. Condensation is a frequent cause of moisture around skylights, especially in Myrtle Beach where indoor humidity levels can run 55 to 65 percent in homes without adequate dehumidification. When warm, moist indoor air contacts the cooler glass surface of a skylight — particularly during winter mornings and late fall evenings — moisture condenses on the glass and drips down.

The distinction matters because condensation is an indoor humidity problem, not a roofing problem. Applying sealant or replacing flashing will not fix condensation. Reducing indoor humidity, improving attic ventilation, or upgrading to a double-pane or triple-pane skylight will. More on how to tell the difference in Section 3 below.

4. Improper Installation

Skylight installation is more complex than most roofing work, and improper installation is behind many leaks that appear within the first 1 to 5 years. The most common installation errors include: flashing not properly integrated with the underlayment and shingles, curb not properly sealed to the roof deck, weep holes blocked by sealant, and the skylight mounted on a curb that is too short for the roof slope.

A particularly common problem is contractor-fabricated flashing rather than the manufacturer's engineered flashing kit. Velux and Fakro both design flashing systems specific to each skylight model and roof type. When a roofer substitutes generic step flashing because it is cheaper or they do not want to order the kit, the result is a flashing system that works adequately during normal rain but fails under the wind-driven rain conditions that are routine in coastal South Carolina. If your skylight leaked within 5 years of installation, improper installation is the most likely cause.

5. Age

Every component of a skylight has a finite lifespan. The glass seal between panes lasts 15 to 20 years before it can fail and fog. The rubber gaskets last 10 to 15 years in coastal sun before hardening. The sealant lasts 8 to 12 years. The flashing metal, depending on material, lasts 15 to 25 years before corrosion creates failure points. A skylight that is 15 to 20 years old in coastal South Carolina is approaching the end of its reliable service life across multiple components simultaneously. At that point, repairing one component often buys only a few years before the next one fails.

6. Storm Damage

Tropical storms and hurricanes cause skylight leaks in two ways: direct impact damage (hail, flying debris cracking or breaking glass) and wind-driven rain forcing water through gaps that are normally weather-tight under calm conditions. Wind speeds of 60 mph or higher can push rain upward under flashing and into the smallest gaps between flashing joints.

Storm damage leaks that appear suddenly after a named storm are often covered by homeowner's insurance. Document the damage with photos before making any repairs and file the claim promptly. Storm damage that worsens pre-existing deterioration is a gray area — the insurer may cover the storm portion but not the underlying age-related degradation.

Why Coastal Skylights Fail Faster

A skylight installed in Columbia, South Carolina — 100 miles inland — will outlast the same skylight in Myrtle Beach by 5 to 10 years. The coast is a fundamentally different environment for every component of a skylight system.

Salt Air Corrodes Flashing Metal

Homes within 5 miles of the Atlantic Ocean are in an active salt corrosion zone. Airborne salt deposits on metal surfaces and accelerates oxidation. Standard galvanized steel flashing — which is what most skylights ship with — develops corrosion pitting within 8 to 12 years in this zone, compared to 20+ years inland. Aluminum flashing resists salt better but still corrodes at fastener points where dissimilar metals contact each other (galvanic corrosion). The corrosion creates pinholes and joint separation that let water through.

UV Degrades Seals Faster

Coastal South Carolina receives approximately 2,800 hours of sunshine per year. That intense UV bombardment breaks down rubber gaskets and sealant compounds at an accelerated rate. The rubber hardens, loses flexibility, and cracks. The sealant dries, shrinks, and pulls away from bonded surfaces. A seal rated for 20 years by the manufacturer is giving you 12 to 15 years in direct coastal sun. South- and west-facing skylights take the worst of it because they receive the most intense afternoon UV during the hottest part of the year.

Wind-Driven Rain Finds Gaps That Normal Rain Does Not

This is the factor most people underestimate. Standard roofing and flashing systems are designed to handle rain falling vertically with gravity. They work by directing water downhill through overlapping materials. During a tropical storm or nor'easter, rain moves horizontally — or even upward under overhangs and flashing edges — driven by 50 to 100 mph winds. Water reaches places it was never designed to go. A flashing joint that stays perfectly dry during a normal thunderstorm leaks like a faucet during a tropical storm because the wind pushes water uphill through a 1/32-inch gap. Coastal homes experience this kind of rain 3 to 6 times per year. Inland homes may never experience it.

Thermal Expansion from SC Heat Cycles

A skylight on a Myrtle Beach roof can see surface temperatures above 160°F on a July afternoon and drop to 70°F after sunset — a 90-degree swing in 6 hours. In winter, it may go from 28°F overnight to 65°F by midday. Every one of those cycles causes the metal flashing, the aluminum or vinyl skylight frame, and the glass to expand and contract at different rates.

Over thousands of thermal cycles, this differential movement opens gaps at the joints between different materials. Sealant that bridges the gap between the metal flashing and the skylight frame gets stretched and compressed repeatedly until it cracks. Flashing joints loosen as the metal creeps. The cumulative effect is that a perfectly sealed skylight gradually develops tiny openings over 10 to 15 years — and those openings are exactly where the next wind-driven rain event enters.

• Salt air corrosion — galvanized flashing develops pitting in 8 to 12 years vs 20+ years inland
• UV degradation — seals and gaskets lose 5 to 8 years of life compared to manufacturer ratings
• Wind-driven rain — 3 to 6 events per year push water into gaps that stay dry during normal rainfall
• Thermal cycling — 90°F+ daily swings in summer loosen joints and crack sealant over thousands of cycles
• High humidity — 75 to 85 percent average humidity increases condensation issues and slows drying of any moisture that enters the framing

Condensation vs Actual Leak: How to Tell the Difference

This is the first question I ask when a homeowner calls about a leaking skylight: where exactly is the water? The answer determines whether you need a roofer or a dehumidifier.

In Myrtle Beach, condensation is especially common in homes that keep windows closed year-round and run air conditioning continuously. The AC removes some humidity, but bathrooms, cooking, and breathing still generate significant moisture inside the home. When that moist indoor air hits the cooler glass of a skylight — particularly in winter or early morning — condensation forms. Running bathroom exhaust fans, using a dehumidifier to keep indoor humidity below 50 percent, and ensuring proper attic ventilation all reduce skylight condensation.

Skylight Leak Repair Options and Costs

Here are the three tiers of skylight leak repair, from least invasive to most comprehensive. The right choice depends on what is actually failing and how old the skylight is.

Tier 1: Reseal — $200 to $500

Resealing involves removing the old sealant around the skylight frame, cleaning the surfaces, and applying fresh roofing sealant or polyurethane caulk. This is the appropriate repair when the flashing is intact but the sealant between the flashing and the frame has cracked or pulled away.

Resealing is effective when the leak is minor and localized to one area, the existing flashing is not corroded or damaged, the skylight itself is in good condition, and the curb framing is solid. In coastal conditions, a professional reseal using high-quality polyurethane sealant lasts 5 to 8 years before the sealant needs refreshing again. Silicone sealant lasts longer but does not bond as well to some flashing materials, so the choice of sealant depends on the specific flashing type.

Tier 2: Reflash — $400 to $1,000

Reflashing means removing the surrounding roofing material around the skylight, stripping the old flashing, installing new flashing (ideally the manufacturer's engineered flashing kit), and relaying the surrounding shingles or roofing material over the new flashing. This is the most common permanent repair for skylight leaks.

Reflashing is the right call when the existing flashing is corroded, bent, or improperly installed, the leak occurs at flashing joints rather than at the glass seal, the skylight unit itself is in good condition with clear glass and functional hardware, and the curb is not rotted.

The cost range depends on the skylight size, roof type, and whether the surrounding roofing material can be reused or needs new material. On a shingle roof, reflashing a standard 22-by-46-inch skylight typically runs $500 to $800. On a metal roof, it can run $600 to $1,000 because the metal panels require more careful work to maintain weather-tight seams.

Tier 3: Full Replacement — $800 to $2,500+

Full replacement means removing the entire skylight unit, inspecting and repairing the curb framing and roof deck as needed, installing a new skylight with the manufacturer's flashing kit, and integrating the new flashing with the surrounding roofing material.

Replacement is the right call when the skylight is over 15 years old and has multiple deterioration points, the glass is cracked, fogged between panes, or discolored, the curb frame is rotted and needs rebuilding, or when you are already having the roof replaced and can bundle the skylight work at a lower marginal cost. The price depends heavily on the skylight size and brand. A standard 22-by-46-inch Velux fixed skylight with flashing kit runs $800 to $1,200 installed. A 30-by-55-inch venting (operable) skylight can run $1,500 to $2,500+. Custom or oversized skylights push the cost higher.

Repair vs Replace: The 15-Year Rule

Here is the decision framework I use with every skylight leak call. It is simple, and it saves homeowners from spending money on repairs that buy only a year or two before the next component fails.

The reason 15 years is the threshold in coastal South Carolina is that multiple components approach end of life around the same time. If you reflash a 16-year-old skylight for $800, the seals and gaskets may fail within 2 to 3 years, meaning another $400 repair. And if the glass seal fails a year after that, you are looking at replacement anyway — having spent $1,200 in repairs that bought maybe 3 years. A $1,500 replacement at the 15-year mark gives you 15 to 20 more years with modern seals, low-E glass, and an engineered flashing system.

Velux vs Fakro vs Custom Skylights

The skylight market is dominated by two major manufacturers — Velux and Fakro — with custom-fabricated skylights filling the remainder. Here is how they compare for coastal South Carolina applications.

Velux is the skylight I install most often and recommend for coastal homes. Their flashing kits are the industry standard — engineered specifically for each model and roof type, with overlapping components that handle wind-driven rain better than field-fabricated alternatives. Their 20-year installation leak warranty (when installed with their flashing kit) provides real protection. Parts availability is excellent, meaning you can replace a glass pane or a gasket without replacing the entire unit.

Fakro is a solid alternative. Their quality has improved significantly in recent years and their pricing is typically 10 to 15 percent lower than comparable Velux units. Their flashing systems are well-engineered and their glass options include the low-E and laminated configurations needed for coastal performance. The main consideration is that their parts network in South Carolina is smaller than Velux, so getting a replacement gasket or glass pane may take longer.

Custom skylights are built to order for non-standard openings — large spans, unusual shapes, or architectural designs that factory units cannot accommodate. Quality depends entirely on the fabricator and installer. The biggest risk with custom skylights in coastal areas is the flashing — without a factory-engineered flashing system, the installer must fabricate flashing from scratch, and the quality of that work varies enormously. Custom skylights cost 2 to 3 times more than factory units and have no standardized warranty. I recommend custom only when the opening genuinely cannot accommodate a standard Velux or Fakro unit.

The Real Cost of Ignoring a Skylight Leak

This is where homeowners get into serious trouble. A skylight leak seems minor — a drip during heavy rain, a small stain on the ceiling. The temptation is to put a bucket under it and deal with it later. The problem is that the water you see is a fraction of the water that is entering. Most of the water travels down through the light well framing, soaking materials you cannot see.

The Damage Timeline

Here is what happens when a skylight leak goes unrepaired in the Myrtle Beach climate, where high humidity keeps materials wet long after the rain stops.

The numbers tell a clear story: a $400 reflashing job that is ignored for a year becomes a $5,000 to $10,000 remediation project. The multiplier is 10x to 25x. In 20 years of roofing industry experience, I have never seen a skylight leak that improved on its own. They always get worse, and they get worse faster in coastal humidity because the wet framing never fully dries between rain events.

Hidden Damage You Cannot See

The visible stain on your ceiling is the tip of the iceberg. Behind the drywall, water is traveling along framing members, soaking insulation, and creating conditions for mold growth. The light well — the shaft between the skylight and the ceiling opening — acts like a funnel that concentrates water onto the wood framing.

• Insulation damage: wet insulation loses its R-value and becomes a mold incubator. Fiberglass insulation absorbs and holds water indefinitely.
• Mold growth: in Myrtle Beach humidity, mold can begin growing within 24 to 48 hours of wood reaching 20 percent moisture content. The light well is dark, warm, and poorly ventilated — ideal mold conditions.
• Framing rot: the 2x4 or 2x6 framing that forms the light well and supports the curb softens and loses structural integrity. Rot spreads through wood framing faster in humid environments.
• Roof deck damage: water that enters around the curb can travel along the roof deck, rotting the plywood or OSB beyond the immediate skylight area.
• Electrical hazard: if the skylight light well contains recessed lighting or electrical wiring, water intrusion creates a potential electrical hazard that goes beyond cosmetic damage.

David Karimi / WeatherShield Approach

When a homeowner calls us about a leaking skylight, we follow a specific diagnostic process to identify the actual failure point before recommending any repair. Too many contractors jump straight to replacing the entire skylight when a $500 reflashing job would solve the problem permanently.

We do not sell unnecessary replacements. If your 8-year-old Velux skylight has a flashing failure, we reflash it with the correct Velux flashing kit and it will be leak-free for another 10 to 15 years. If your 18-year-old no-name skylight with fogged glass and corroded flashing is leaking, we will be honest that a replacement is the smarter investment.

We serve homeowners throughout Myrtle Beach, Conway, North Myrtle Beach, Surfside Beach, Pawleys Island, and the surrounding Horry and Georgetown county areas.

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