Skylights are the single most common failure point on premium roofs in Florida. The reason is the same on every brand and every material: the interface between the skylight frame and the surrounding roof field is a four-sided waterproofing detail that must accommodate thermal movement, wind-driven rain, and the manufacturer's flashing kit.
Three rules govern getting it right.
Rule 1: Use the manufacturer's flashing kit, not generic flashing
Velux, Sun-Tek, and other premium skylight manufacturers produce flashing kits specifically engineered for their products. The kits are matched to the skylight's frame geometry, the expected thermal movement, and the recommended attachment method.
Generic flashings (cobbled together from sheet copper or aluminum) sometimes work and often do not. The manufacturer's flashing kit is the warrantied detail; deviating from it voids the skylight warranty.
The cost of the manufacturer kit is $300-$1,200 depending on size. The cost of a leak at the skylight is substantially more.
Rule 2: Integrate with the surrounding field at the right elevation
The flashing kit has an upper, lower, and two side flashings. Each must be set at the correct elevation relative to the surrounding tile or metal. Common errors:
- Side flashing below tile: the wrong installation; water runs under the flashing and into the building.
- Side flashing above tile: the right installation; water runs onto the flashing and away.
- Upper flashing buried under tile: water cannot get past the flashing and ponds.
- Lower flashing on top of tile: water cascading over the lower edge has nowhere to go.
The integration is layered: upper flashing tucked under upslope tiles, side flashings cascaded over side tiles, lower flashing terminating onto downslope tiles. The skylight manufacturer's installation manual specifies this; following it is non-negotiable.
Rule 3: Specify the right skylight for the roof
Not every skylight is appropriate for every roof material:
- Tile: requires a curb-mounted skylight, raised at least 4 inches above the tile field, with flashing kit specifically rated for tile installation.
- Slate: same as tile, with the curb height matched to the slate thickness.
- Standing-seam metal: deck-mounted skylights with the manufacturer's metal-specific flashing kit; the kit must accommodate the panel profile.
- Asphalt: deck-mounted skylights with standard step-flashing kit.
A skylight specified for asphalt and installed on tile will leak. The mount style and the flashing kit must match the field material.
What we do differently
Two things, beyond the rules above:
Pre-flashing inspection
Before installing the skylight, we set the area around it with the field material to the rough opening. Then we set the skylight and its flashing kit. The order matters: the field is committed first; the skylight integrates with the existing field.
The reverse order — install the skylight first, then bring the field up to it — produces awkward cuts and partial-tile dimensions that compromise the detail.
Annual inspection cycle
Skylights are inspected annually as part of our maintenance program. The flashing kit, the curb-to-field interface, and the seal on the skylight itself are all checked. Any seal failure is addressed before the next storm cycle.
What to ask if you have an existing leaking skylight
Three diagnostic questions:
What is the brand of the skylight, and is the original flashing kit still in place? Original flashing kits last 25-40 years; aftermarket repairs less.
Is the leak at the flashing or at the skylight itself? Flashing leaks are fixable; skylight unit failures (seal between glass and frame) require replacement.
Has the surrounding roof been disturbed since installation? Sometimes the skylight is fine and the leak is from a re-roof that damaged the flashing integration.
A skylight that was correctly installed and has not been disturbed will rarely leak in the first 25 years. Almost every skylight leak we have walked began with a botched installation or a subsequent disturbance.
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