How to Check Roof Flashing Around a Skylight (5 Steps)

TL;DR: Most skylight leaks come from failed flashing, not the glass unit itself, and flashing typically lasts 15-20 years before sealant and metal seams start to fail. Check the four flashing pieces (head, step, apron, and side) from the ground with binoculars first, then from a ladder for cracked caulk, rust streaks, and lifted metal, especially after a hard freeze or a windstorm.

_Last reviewed: July 2026 · 7 min read_

A stain spreading across your ceiling under a skylight almost never means the skylight itself is broken. It means water found a gap in the metal flashing wrapped around it, and that gap has probably been there for months before you noticed the drip. Here's how to find it before the drywall does.

Okoniq Property Hub logs your last roof inspection date and flags when a skylight or flashing check is due, so you're not guessing whether it's been one year or five.

What is skylight flashing, and why does it fail first?

Flashing is the metal skirt, usually aluminum or galvanized steel, that wraps the base of a skylight and directs water around the opening instead of through it. It fails before the skylight glass because it's the part doing the actual water-shedding work, while sealant, solder joints, and overlapping metal seams take the brunt of thermal expansion, UV exposure, and ice.

A typical flashing kit has four sections: the head flashing at the top (uphill side), step flashing running down both sides in overlapping pieces tucked under each shingle course, and the apron or sill flashing at the bottom (downhill side) that laps over the roofing below it. Manufacturers rate most kits for 15 to 20 years, but sealant beads at the corners often give out in half that time, especially in climates with hard freeze-thaw cycles.

If your roof is original to the house and older than 15 years, the flashing is worth checking even without visible signs, the same way you'd check attic ventilation balance before assuming your attic is fine just because nothing's dripping yet.

How do you inspect flashing without climbing on the roof?

Start from the ground with binoculars, looking for lifted metal edges, dark streaking below the flashing line, or missing shingle tabs near the skylight corners. This gets you 70% of the way to knowing if there's a problem, because major flashing failures are usually visible as gaps or rust trails even from 20 feet below.

For the closer look, use a stable extension ladder set up on firm, level ground, and only go as high as the eaves unless you're comfortable on a roof with proper fall protection. From there, check:

• Caulk or sealant at flashing seams for cracking, shrinking, or gaps you can fit a fingernail into
• Rust streaks running down from any exposed nail heads or metal seams
• Lifted or curled step flashing pieces along the sides, especially the top two courses nearest the skylight
• Granule loss or bare spots on shingles directly around the flashing, which points to water sitting there repeatedly

If you're not confident on a ladder, this is a reasonable one to hand to a roofer, the same call you'd make before tackling attic mold remediation yourself versus bringing in a pro.

What are the warning signs of a flashing leak from inside the house?

The clearest sign is a ceiling stain that appears or grows after a heavy rain, wind-driven storm, or the first spring thaw, not during dry weeks. Water tracks along framing before it shows up on drywall, so the stain's location doesn't always sit directly under the leak point, it can appear a foot or two to one side.

Other interior signs include a musty smell in the room below the skylight even when no stain is visible yet, peeling paint or bubbling drywall texture near the skylight well, and condensation that keeps reappearing on the inside of the skylight frame even in mild weather. That last one can also mean poor insulation around the shaft rather than a flashing leak, so it's worth ruling out both.

| Sign | Likely Flashing Issue | Likely Not Flashing | |---|---|---| | Stain appears only after storms | Yes, active leak point | — | | Stain is constant, slowly growing | — | Could be condensation from poor shaft insulation | | Rust streaks visible outside | Yes, corroded seam | — | | Musty smell, no visible stain | Possible early leak or trapped moisture | Could be inadequate attic airflow |

If moisture is pooling anywhere near the skylight shaft or attic space, it's worth checking whether nearby basement waterproofing issues or general moisture problems in the home are compounding the picture, since houses with one water-management gap often have more than one.

When should you reseal versus replace the flashing?

Reseal when the metal itself is intact and the failure is limited to cracked or missing caulk at the seams, which is a $50-150 fix using roofing-grade polyurethane sealant, not standard silicone caulk, which shrinks and fails faster in sun exposure. Replace the flashing kit entirely when you see rust-through, bent or separated metal pieces, or more than one prior repair attempt already failed at the same spot, since patched flashing rarely holds as long as a fresh install.

A full flashing replacement on an existing skylight typically runs $300-700 done by a roofer, depending on roof pitch and whether shingles need to be pulled back and relaid. That's meaningfully cheaper than the $2,000-5,000+ in drywall, insulation, and mold remediation that a slow leak left unchecked for a year or two can cause. If you also notice attic humidity issues nearby, pair the flashing fix with a look at bathroom fan venting to attic fix, since misdirected exhaust vents often get blamed on skylight leaks when they're a separate moisture source entirely.

FAQ

How often should skylight flashing be inspected?

Check it once a year, ideally in spring after the freeze-thaw season, and again after any major windstorm or hailstorm that hits your area.

Can you fix skylight flashing without removing the skylight?

Yes, for sealant failures you can recaulk seams from the outside without pulling the unit, but full metal replacement usually requires temporarily lifting the surrounding shingles.

Does homeowners insurance cover skylight flashing leaks?

Sudden storm damage is often covered, but gradual leaks from worn-out flashing that went unaddressed for years are typically treated as a maintenance issue and excluded.

How long does skylight flashing last before it needs replacing?

Most flashing kits last 15-20 years, though sealant at the seams often needs attention around the 7-10 year mark even if the metal itself is still sound.

What's the difference between step flashing and apron flashing?

Step flashing runs in overlapping pieces along the sides of the skylight, tucked under each shingle course, while apron flashing is a single piece at the bottom that laps over the roofing below to shed water downhill.

This is educational information, not professional roofing advice. Call a licensed roofer if you're unsure about climbing on your roof or diagnosing a leak's exact source.