How skylights leak, what flashing and placement actually prevent it, repair-vs-replace guidance, and how to coordinate skylight work with a New Jersey roof replacement.
A skylight brings daylight into dark rooms — and, installed poorly, brings water in too. Most skylight problems are not the skylight; they are the flashing and the installation. Here is what New Jersey homeowners should understand before installing, repairing, or replacing one.
Why skylights leak
The overwhelming majority of skylight leaks come from failed flashing — the layered metal that ties the skylight into the surrounding roof — or from old, hardened sealant, not from the glass. A skylight curb that was reused with old flashing during a reroof is a classic leak waiting to happen. Cracked seals and condensation can mimic leaks too.
Flashing is everything
A correctly installed skylight uses a proper flashing kit integrated with the roofing — head, sill, and step flashing layered so water is directed over, not into, the assembly. Relying on a bead of caulk instead of real flashing is the single most common installation failure. Quality sealant has a role, but only as a complement to flashing.
Waterproof Flashing & Seam Tape
Seal flashing edges and small seams.
Handy for minor maintenance between professional visits.
Roof & Membrane Sealant
Flexible sealant for roof penetrations.
Re-seal pipe boots and flashing; check substrate compatibility.
Dripless Caulk Gun
Clean application of sealant.
Controlled beads for flashing and skylight sealing tasks.
Affiliate disclosure: links above are Amazon affiliate links. As an Amazon Associate we earn from qualifying purchases, at no extra cost to you. Learn more.
Repair or replace?
If the skylight unit itself is sound and fairly new, a flashing or seal repair may solve a leak. But if the unit is old, fogged between panes, or you are reroofing anyway, replacing the skylight at the same time as the roof is almost always the smart move — the area is already open, and a new unit with a new flashing kit resets the clock.
Coordinate skylight work with your roof
The best time to install or replace a skylight is during a roof replacement. The flashing can be integrated into the new roof from the start, the warranties align, and you avoid paying twice to open the same area. If a roofer proposes reusing old skylight flashing on a new roof, ask why — it is a common shortcut that causes future leaks.
Placement and type
Fixed skylights are simplest and most leak-resistant; venting (operable) skylights add airflow but more moving parts. North-facing slopes give even light; south-facing add heat gain. On a low-slope or flat roof, a curb-mounted unit with proper height keeps water out. A pro can advise on placement for both light and weather performance.
DIY limits
Resealing accessible flashing edges with the right product is within reach for a careful homeowner, but cutting a new roof opening, integrating flashing, and maintaining the roof's warranty is professional work. Botched skylight installs are a leading cause of stubborn roof leaks — this is a place to hire it out.
Frequently asked questions
Why is my skylight leaking?
Most skylight leaks come from failed flashing or old sealant rather than the glass itself. Reused flashing from a previous roof and hardened caulk are common culprits; condensation can also mimic a leak.
Should I replace my skylight when I replace my roof?
Usually yes, especially if the skylight is old or fogged. The area is already open, new flashing can be integrated from the start, and the warranties align — avoiding a future leak and a second job.
Can I fix a skylight leak myself?
Resealing accessible flashing with the correct product can be DIY for a careful homeowner, but flashing integration and any roof-opening work should be done by a professional to protect against leaks and preserve warranties.