Skylight leak repair for Jersey City stairwells and top floors

Most skylight leaks we open up on Jersey City rowhouses are not coming through the glass at all. They start at the curb, the short wood or metal box the unit sits on. On a flat roof that curb is wrapped with base flashing, and over the years the corners split, the laps shrink back, and water that sheets across the roof during a nor'easter runs in behind the flashing. From inside, the stain looks like a skylight problem, so that is what owners call it.

Condensation is the other suspect, and it fools plenty of people. In January, warm moist air from a bathroom or stairwell rises into the skylight well and meets cold glass or a thin acrylic dome. Water beads, runs down the inside of the frame, and drips onto the stair landing. If the drips show up on cold, dry mornings rather than during rain, that points to condensation. We check both, because the fixes are completely different and nobody should pay for flashing they don't need.

A quick way to tell them apart before we arrive: note when it drips. Rain plus wind from one direction usually means a curb corner or a side lap. A steady drip while snow is melting on the roof suggests the flashing sits too low for the snow line. Frost or droplets on the inside of the dome with no weather outside is moisture from the house. Tell us what you saw when you call; photos help.

The curb is where the skylight meets the waterproofing, and it behaves like any other roof penetration. A real repair cuts back the failed flashing and dried sealant, primes the curb, and installs new base flashing with reinforced corners that ties into the field membrane with proper laps. Where the unit design allows, a metal cap or counterflashing covers the top edge. Caulk smeared over a split corner looks tidy for a few months, then sun and cold open it again, so we don't sell it as a fix.

Height matters as much as the seal. Many older curbs sit only a few inches above the finished roof, so ponding water or packed snow climbs right over the flashing. When the curb is low or soft with rot, we rebuild it to a proper height before flashing. If water collects around the skylight because the roof dishes toward it, a small cricket or ponding water repair steers water away, and that detail often separates a skylight that leaks again in two winters from one that stays dry. The same methods apply in roof flashing repair elsewhere.

Downtown and around Hamilton Park, many brick rowhouses still have a skylight over the top stair, sometimes an old wired-glass unit in a steel frame, sometimes a plastic dome added decades later. Wired glass cracks along the wire when the frame rusts and swells, and the putty that held the panes dries to powder. Acrylic domes yellow, turn brittle under strong summer sun, and crack from hail or a dropped tool. A single short crack can be sealed as a stopgap; once a dome is crazed across its face, patching only buys a season.

Frames matter as much as glazing. Steel frames rust from the bottom rail up, aluminum frames lose their gaskets, and wood curbs underneath rot where water has been sitting for years. We probe the curb with an awl before we commit to anything. When the dome is cracked through or the frame has rusted past resealing, swapping the unit is simply the step that stops the leak. We match the curb size where we can so the deck opening stays the same, and an insulated dome cuts condensation at the same time.

Skylights usually sit right over a stairwell, which means a hole in the roof directly above the only way in and out of the building. We stage materials before anything is opened, cover the stairs below with drop cloths, and keep a temporary cover ready in case a summer thunderstorm rolls in early. In a multi-unit building we let tenants know when the stair will be dusty and for how long.

We also look at what surrounds the skylight. If the field membrane around the curb is cracked or patched to exhaustion, sealing the curb alone just moves the leak a foot over, so we'll show you the condition and suggest flat roof leak repair or a wider waterproofing scope where it's needed. If the whole roof membrane is beyond repair, it needs replacing, and the skylight curb gets flashed into the new surface.