Skylights and roof hatches leak at the curb and the flashing long before the glass ever fails. Here is how Chicago owners inspect, reseal, and schedule the work before fall rain arrives.
Chicago's building stock is full of skylights nobody thinks about until water shows up on a top-floor ceiling. Vintage two-flats and greystones in Logan Square and Wicker Park often carry a stairwell skylight or an interior light well left from the days before electric lighting reached every landing. Mid-rise buildings in Lakeview and Rogers Park usually have a roof hatch with a small domed unit over the top stair run. Both sit on flat or low-slope roofs, so water does not run off on its own. It pools, sits, and looks for a seam.
The failure is almost never the glass or the acrylic. It is the curb the unit sits on, the flashing tying that curb into the roof membrane, and the sealant bead at the edge of the dome. Chicago's freeze-thaw swing works those joints harder than almost anything else on the building: the membrane contracts in January, expands in July, and sealant that was flexible five years ago turns chalky and pulls away from the metal.
Timing matters more here than on most maintenance items. Right now the roof is dry, the membrane is warm and pliable enough for a patch or new sealant bead to actually bond, and you have weeks before the fall rain pattern settles in. A repair made in late October on a cold membrane rarely seals the way it should. A repair made in January is a tarp with an invoice attached.
There is a scheduling argument too. Fall turnover work is already putting crews in the building for painting, cleaning, and punch lists ahead of September and October move-ins. Folding a roof-side inspection into that visit costs a fraction of an emergency call after the first heavy storm, when every roofer from Andersonville to Evanston is booked three weeks out.
Start with the curb. A skylight curb should stand four to eight inches above the finished roof surface. On older Chicago buildings, decades of re-roofing have often raised the membrane so the curb is now only an inch or two proud, which puts the flashing right in the path of standing water. That is a rebuild, not a reseal, and it is worth knowing before you spend money on sealant.
Then work the details: flashing laps lifted at the corners, sealant beads cracked or shrunken away from the metal, fasteners backing out of the frame, gasket material gone hard around a hatch lid. Look for ponding — a dark ring or silt line on the membrane tells you water sat there after the last storm. Clear leaves and grit from the upslope side of every curb, since debris dams are what turn a minor low spot into a two-inch pond. Finally, check acrylic domes for crazing, yellowing, or the fine star-shaped cracks hail leaves behind.
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