Homeowner Guides

Skylights and Roof Leaks: What Maryland Homeowners Should Know

Skylights are one of the most-loved features in a Maryland home — and one of the most common reasons a homeowner calls us about a leak. Here's what surprises most people: the glass is almost never the problem. When a skylight leaks, the cause is almost always the flashing around it, the installation details under the shingles, or simple age. Here's how to tell what you're actually dealing with — and when to re-flash versus replace.

Seeing a water stain right now and not sure whether it's the skylight or the roof? The fastest path to an answer is an inspection. We offer free on-roof and in-attic inspections — request a free inspection or call (301) 458-1003. But if you want to understand the problem first, read on.

Why Skylights Are the Leak-Prone Part of Any Roof

A skylight is a hole cut through your roof's waterproofing system, and water is relentless about finding holes. Everywhere else, your roof sheds water by gravity, shingle-over-shingle, with nothing interrupting the flow. A skylight breaks that pattern in all four directions: runoff hits the upper edge and must be diverted around it, and wind-driven rain — common in Maryland storms — can push water upslope, working against the natural shedding order.

That's why a skylight isn't really a window installation — it's a flashing installation that happens to include a window. The unit sits on a curb (a raised wooden frame), and the waterproofing job is the flashing assembly tying that curb into the roof system.

Skylight vs. Roof Leak: How to Tell the Difference

Water rarely drips straight down from where it enters. It runs along the underside of the decking and shows up wherever gravity takes it — so a ceiling stain doesn't automatically mean the skylight is the culprit. If the stain, bubbling paint, or drip is on the skylight's interior shaft or well (the tunnel between the glass and your ceiling), the skylight or its flashing is the likely source. If the stain is on the flat ceiling several feet away, the entry point could be elsewhere — a valley, a plumbing vent, damaged shingles above — and the water is traveling to where it shows.

Timing tells you a lot too. A stain that appears only during heavy, wind-driven rain but stays dry in light drizzle points toward a flashing detail that wind pushes water past — classic skylight flashing behavior. A stain that grows steadily through any rain, or appears even in dry weather, points toward condensation (more on that below) or something other than the skylight entirely.

The definitive test is a controlled water test: soak with a garden hose starting at the bottom of the skylight and working upward while someone watches inside. Water entering only when the upper flashing is soaked confirms a flashing leak; water at the glass seal points to the unit itself. This is exactly what we do during a professional roof inspection.

Flashing: Where Most Skylight Leaks Actually Come From

Most skylight leaks we investigate come down to a handful of flashing failures — and every one is an installation detail, not a product defect:

• Missing or incorrect step flashing. The sides of a skylight curb need step flashing — small L-shaped pieces interleaved with each course of shingles, so every layer sheds over the one below. When a skylight is “flashed” with a single long piece of metal or just caulk, there's no layered defense.
• No counter-flashing. Counter-flashing covers the top edge of the step flashing so water can't get behind it. Without it, the top of the flashing assembly is an open invitation.
• Caulk used as waterproofing. Caulk is a sealant, not a flashing system. A skylight sealed with caulk instead of proper flashing will leak as soon as the caulk ages and cracks — and it will.
• Reused flashing after a re-roof. When a roof is replaced and the skylight flashing is bent back, re-nailed, and covered with new shingles, it's now pierced with old nail holes and deformed. It will leak — often within a season or two of the new roof.
• Fasteners through the flashing. Nails driven through step flashing in the wrong place create direct water entry points. Proper skylight flashing kits specify exactly where fasteners go — never through the water channel.

Condensation vs. a Real Leak

In Maryland's humid climate, a surprising number of “skylight leaks” turn out to be condensation — warm, moist indoor air hitting the cold glass and condensing into droplets that drip off the frame. It looks like a leak, wets the drywall, and can grow mold on the shaft walls. But no amount of flashing work will fix it, because water was never coming in from outside.

Here's how to tell them apart. Condensation beads on the glass and interior frame — the coldest surfaces in the room — and it's worst in cold weather and during steamy activities like showers, cooking, and laundry. A real leak shows on the shaft walls or the surrounding ceiling and tracks with rain. If your skylight drips on a clear January morning after everyone's showered, that's condensation. If it drips during rainstorms and not otherwise, that's a leak.

Condensation is usually a ventilation and humidity problem, not a roofing problem — bathroom and kitchen fans venting into the attic, a humidifier set too high, or a poorly ventilated attic. Our roof ventilation mistakes guide covers the details — worth reading before you pay anyone to re-flash a skylight that isn't leaking.

Age of the Skylight vs. Age of the Roof

The trickiest skylight situations come from mismatched ages. The skylight was installed with the original roof; then the roof got replaced while the skylight stayed. Now you have a new roof with an older skylight — and older flashing that may or may not have been replaced with the roof. This is the most common setup behind post-replacement skylight leaks.

Age also changes what the skylight itself is. Older generations — the plastic bubble domes and early curb-mounted units — were built to different standards than modern glass skylights, and their seals don't last as long. If your skylight fogs between the panes, that's a failed seal: its insulating value is gone, and no flashing repair will change that. Fogging is a replace signal, full stop. A modern glass unit with clear glass and a sound frame is usually a re-flash candidate. Our signs you need a new roof guide puts the skylight decision in the bigger picture of your roof's overall age.

Re-Flash vs. Replace the Skylight: How to Decide

Re-flash when the skylight unit itself is sound: the glass is clear (no fogging between panes), the frame is solid with no cracks or warping, the curb is solid wood, and the leak clearly traces to the flashing detail. A proper re-flash removes the surrounding shingles, installs a new flashing kit (step flashing, head flashing, apron/sill flashing, and counter-flashing) with ice-and-water shield around the curb, and re-shingles the area. Done right, this permanently fixes a flashing leak.

Replace when the unit itself is failing: fogged or cracked glass, a cracked or deteriorated frame, a rotted curb, a dome-style or outdated unit, or a leak history suggesting the unit was never installed correctly. Replacing means a new skylight and new flashing — never a new skylight dropped into old flashing. If your roof is also nearing the end of its life, see our repair vs. replace guide for the broader decision.

The red flag: be wary of any contractor who recommends replacing every skylight on every re-roof as a blanket rule, or one who reflexively re-flashes units at the end of their life. The right answer depends on your specific unit, and it should be justified with what we can see.

The Cheapest Time to Deal With a Skylight (During Tear-Off)

If you're already replacing your roof, the skylight decision should be made before the job starts — not discovered mid-project. During a tear-off, the roof is open: the flashing is fully accessible, the curb is exposed for inspection, and the crew is already on the roof. There's no additional shingle removal, no disturbing a finished roof, and no second mobilization. It is, by a wide margin, the most efficient time to re-flash or replace a skylight.

Doing it after a new roof goes on means cutting into and patching brand-new shingles — doable, but more labor and a visible patch. A thorough estimate addresses every skylight up front: re-flash, replace, or leave alone, each with a stated reason.

What a Proper Skylight Install Includes

Whether it's new flashing or a new unit, here's what a correct installation involves — use this as your checklist when reviewing a quote:

• Curb inspection and repair. The wooden curb gets inspected, and any rot is repaired or rebuilt before anything else goes on.
• Ice-and-water shield around the curb. A self-sealing membrane wraps the curb and extends onto the decking — critical backup in Maryland's freeze-thaw winters and wind-driven rain.
• A complete flashing kit. Step flashing interleaved with each shingle course up both sides, head flashing across the top, apron or sill flashing at the bottom, and counter-flashing over the assembly — every piece in place, fastened where the kit specifies.
• No reliance on caulk. Sealant has a role at specific joints, but it is never the primary waterproofing. Any install that depends on a caulk bead to keep water out is temporary by design.
• The interior side too. The shaft or well should be checked for moisture damage, and the unit's weep system (the designed drainage path) must be left clear — not caulked shut.

Red Flags When a Contractor Quotes Skylight Work

• “We'll just caulk it.” A caulk-only fix for a flashing leak is a patch with a short lifespan. If caulk is the entire plan, the real problem hasn't been addressed.
• Reusing old flashing. Flashing with old nail holes and bent metal won't outlast your new roof.
• No mention of the curb. The curb is the foundation of the whole assembly. A quote that never addresses its condition is a quote from someone who hasn't really looked.
• No attic inspection. Skylight leaks leave evidence in the attic — staining on the decking and framing that shows where water actually traveled. A diagnosis made from the ground alone is incomplete.
• Pressure to decide on the spot. A leak feels urgent, and some contractors use that. A day or two for a second opinion won't change the outcome; a rushed wrong repair will.

Proudly Serving These Maryland Communities

Nucci Brothers Roofing diagnoses and repairs skylight leaks — and installs new skylights correctly during roof replacements — for homeowners in Annapolis (where historic homes often carry aging skylights), Baltimore (rowhome skylights), Rockville, Columbia, and Bowie — plus skylight evaluations across Maryland. Request a free inspection or call (301) 458-1003 — MHIC #24398, TAMKO Certified, serving all of Maryland since 1986.