Solving Common Skylight Problems: Leaks, Condensation, and More

The most common skylight problems are leaks from failed flashing, condensation dripping off cold glass in winter, fogging between the panes, and cracked or aging glass, and the good news is that all four are fixable. Roughly two thirds of the skylight leaks we get called about in Western PA aren’t actually the skylight failing, they’re the flashing or the roofing around it. Repairs typically run $300 to $800, while a full skylight replacement usually lands between $1,500 and $3,500 installed, and it’s cheapest when done during a roof replacement.

We’ve repaired and replaced hundreds of skylights around Irwin, Murrysville, and the greater Pittsburgh area since 1995, so here’s our field guide to what goes wrong up there and what to do about it.

Problem 1: A Skylight That Leaks in the Rain

A skylight leaking during or right after rain almost always points to one of three culprits:

• Failed or improper flashing. The metal flashing kit that weaves the skylight into the surrounding shingles is the number one failure point. If the original installer skipped the manufacturer’s kit and relied on caulk and roof cement, it was a countdown from day one. Sealant weathers out in 5 to 10 years under our freeze and thaw cycles.
• Worn roofing around the unit. Shingles crack and lift as they age, and the area around a skylight sees concentrated water flow. Sometimes the skylight is innocent and the roof is the problem.
• Failed seals on the unit itself. Skylights older than 15 to 20 years often leak at the frame or the glass gasket, especially budget units from the 1990s.

Before you call anyone, note when the water shows up. Leaks that appear only during heavy wind driven rain suggest flashing. Water that shows up in winter without rain is usually the next problem on our list, or an ice dam. Our post on how to find a roof leak walks through tracing water back to its real entry point, which is often uphill from the stain on your ceiling.

Problem 2: Skylight Condensation That Looks Like a Leak

Here’s one that fools homeowners every winter. You spot water dripping from the skylight in January, there hasn’t been rain in a week, and you assume the worst. Nine times out of ten, that’s skylight condensation, not a leak. Warm, humid indoor air rises, hits the cold glass, and condenses, and enough of it will bead up and drip onto the floor below.

Bathrooms and kitchens are the usual suspects because they pump moisture into the air. The fixes, in order of cost:

1. Run the bath fan during showers and for 20 minutes after, and make sure it vents outside rather than into the attic.
2. Keep indoor humidity between 30 and 45 percent in winter. A cheap hygrometer tells you where you stand.
3. Check the insulation around the skylight shaft. A poorly insulated shaft makes the glass colder and the condensation worse.
4. If the unit is a single pane or an early double pane model, upgrade. Modern glass with low emissivity coatings and argon fill stays warm enough on the inside surface that condensation mostly stops.

Problem 3: Fog Between the Panes

If the skylight looks permanently cloudy and cleaning doesn’t help, the insulated glass seal has failed and moisture has gotten between the panes. There’s no practical repair for that, and it means the unit has lost its insulating value too. Replacement is the fix, and it’s worth doing sooner rather than later because a failed seal often precedes a frame leak by a few years.

Problem 4: Cracks, Hail Damage, and Plain Old Age

Hail season gives Westmoreland County a beating some years, and skylights take hits that shingles shrug off. Acrylic dome skylights, common on homes and additions from the 1980s and 1990s, get brittle with UV exposure and crack. Glass units fare better, but a direct hit from large hail can still break them. If a storm cracks your skylight, cover it temporarily and treat it with the same urgency as missing shingles, because an open skylight can let a shocking amount of water in fast. Our guide on emergency roof repair covers how to protect the opening until a crew arrives, and storm damage like this is often covered by homeowners insurance.

The Smartest Time to Replace a Skylight

Here’s the advice we give every customer planning a new roof: replace the skylights at the same time, even if they seem fine. Skylight replacement during roof replacement saves real money because the roof around the unit is already open, so you skip the cost of cutting in and reworking shingles later. Adding new skylights during a reroof typically costs $1,000 to $2,000 each, versus $1,500 to $3,500 as a standalone project.

There’s a lifespan logic too. A skylight lasts 20 to 25 years and a new roof lasts 25 to 30. Keep a skylight that’s already 15 years old, and you’ll be cutting into a perfectly good roof in a few years to swap it, and any future leak at that old unit puts your new roof’s warranty coverage in question. We install Velux units, which carry a warranty of no leaks for 10 years when installed with their flashing kits, and we flash every one into the roof system properly.

When Repair Makes Sense

Not every problem means replacement. If your skylight is under 15 years old and the glass is clear, new flashing or targeted roof repair around the unit usually solves a leak for $300 to $800. Condensation issues are often solved with ventilation and humidity control that cost almost nothing. Where we draw the line: fogged glass, cracked frames, discontinued models with no available parts, or any unit that’s leaked more than once after repairs. At that point you’re paying repeatedly to keep a failing unit on life support.

Frequently Asked Questions

Why is my skylight leaking when it rains?
Usually the flashing, not the skylight. Flashing and sealant around the unit fail years before the skylight itself does, especially when the original installer used caulk instead of a proper flashing kit. A repair typically runs $300 to $800.

How do I stop condensation on my skylight in winter?
Lower your indoor humidity below about 45 percent, run bath and kitchen fans longer, and check the insulation in the skylight shaft. If the unit is an older single or double pane model, upgrading to modern insulated glass usually ends the problem.

How long do skylights last?
Plan on 20 to 25 years for a quality unit. Acrylic dome skylights from the 1980s and 1990s often fail sooner. If yours is past 15 years old and you’re reroofing, replace it while the roof is open.

Should I replace my skylight when I replace my roof?
Yes, in almost every case. It costs $1,000 to $2,000 per unit during a reroof versus $1,500 to $3,500 later, and pairing their lifespans means you won’t cut into a new roof in a few years to swap an old skylight.

Got a Skylight Acting Up?

Whether it’s dripping, fogging, or just older than you’d like, we’ll inspect it along with the roof around it and give you an honest answer on repair versus replacement. The inspection is free. Schedule yours at mybellaroof.com or call Bella Construction at 724 515 5163.