How Do I Fix a Leaking Skylight?

Q: How do I fix a leaking skylight?

Most skylight leaks are not the skylight. They are the flashing around it — the curb flashing, the head flashing above it, and the way the roof covering laps over both. Water gets behind a short or corroded flashing and appears at the inside edge of the shaft, which looks exactly like a leaking window. The next most common cause is the perimeter seal or gasket, which dries out and shrinks after fifteen or twenty years of ultraviolet exposure, especially on older acrylic domes. After that comes condensation: a single-glazed or aluminium-framed unit sweats in humid weather and drips, and no amount of roof work will stop it. The repair is chosen by which of those it is. Rebuilding the curb and head flashing, resealing or replacing gaskets, or replacing the unit outright — and a proper diagnosis will tell you which, with photographs, before you spend anything.

Flashing failures

A skylight sits on a curb, and that curb needs step or continuous flashing up its sides, a head flashing that carries water around the top, and roof covering lapped correctly over all of it. Any of those being short, corroded, sealant-dependent or installed out of sequence lets water behind the assembly.

The classic failure in this county is corroded head flashing on an older tile roof, where the metal has thinned from the underside while looking presentable from above. Rebuilding that detail in new metal is a permanent fix, not a patch.

Seals and gaskets

Acrylic and polycarbonate domes are held by gaskets and sealant beads that have a service life. When they dry and crack, water enters at the dome-to-frame joint and runs down inside the frame.

Resealing works when the frame and dome are otherwise sound. When the dome has crazed, yellowed or cracked from UV, replacement is the honest answer — a resealed brittle dome will leak again within a season or two.

Condensation, not leakage

Condensation appears as even dampness or small drips around the whole perimeter of the shaft, often in cool humid weather rather than in rain. Older single-glazed units and aluminium frames without thermal breaks do this routinely.

The fixes are ventilation, humidity control in bathrooms and kitchens, or replacing the unit with a modern insulated one. We would rather tell you it is condensation than sell you flashing you do not need.

Reseal, re-flash, or replace

Re-flash when the metal has corroded or was detailed wrong and the unit is sound. Reseal when the gaskets have aged and the dome and frame are good. Replace when the dome is crazed or cracked, the frame is corroded, or the unit is a 1980s builder-grade dome that has been resealed once already.

If we are replacing, the flashing gets rebuilt as part of the job — there is no sense putting a new unit back on old metal.

Costs and cautions

Skylight repairs generally fall inside the usual $1,200–$2,000 repair range, with replacement of the unit itself depending on size and glazing. Storm-damaged skylights get tarped at $300–$600 first if rain is imminent.

One caution: caulk is not a skylight repair. A ring of sealant around the outside of a curb hides evidence, traps water and buys weeks. It is also the single most common thing we find when we are called out to a skylight that has been leaking for years.

In San Diego County and along the coast

Skylights are common across San Diego County because natural light is cheap here — long hallways in Carlsbad, Escondido and San Marcos tract homes almost all have them, as do additions and remodels throughout the city of San Diego.

Coastal salt air in Oceanside, Carlsbad, Encinitas, Del Mar and Solana Beach eats skylight flashing and fasteners faster than anything else on the roof, so re-flashing is the usual repair there. Inland in Escondido, Poway, Ramona and El Cajon, intense UV and heat cycling craze acrylic domes and dry out gaskets, so resealing and replacement dominate. Marine-layer humidity along the coast also makes condensation a genuinely frequent misdiagnosis.

How Spot Roof Repair solves this for you

We are a repair-only roofing company based in Carlsbad, working the whole of San Diego County — coastal North County, inland, the city of San Diego, East County, the South Bay and the backcountry. We come out, find the actual cause, photograph it, and hand you a written price before anyone starts work.