Skylight Installation
Updated November 6, 2026
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Safety
Roof work carries serious fall risks, and an open cut in the roof deck weakens the structure until framing and glazing are complete. Anyone attempting a do-it-yourself install should wear a harness anchored to a rated point, keep the area below the opening clear, shut off power before cutting near wiring, and stay off the roof when it is wet, icy, or windy. Structural changes to rafters may require permits and load calculations, so local building codes should be reviewed before any cutting begins.
Before the visit
Before installation day, clear the attic space around the planned opening, move fragile items out of rooms below, and confirm the selected skylight matches the roof pitch and covering type. Mark the location between rafters where possible, gather the flashing kit, sealant, framing lumber, and interior finish materials, and check the forecast to avoid working ahead of rain. A ladder rated for the roof height and a helper for lifting the unit keep the project moving safely.
Repair vs replace
Repair makes sense when the glass is intact but leaks trace to failed sealant, cracked or lifted flashing, clogged weep holes, or loose fasteners. Condensation between panes with no active water entry, minor drywall cracks at the frame, or a sticky venting mechanism can often be corrected without replacing the unit. If the frame is sound and the leak source can be identified, targeted repairs frequently restore performance at a fraction of replacement cost.
When to replace
Replacement is usually the better path when the frame is rotted or corroded, the insulated glass seal has failed with persistent fogging, the unit is an older single-pane model, or leaks continue after flashing repairs. Cracked or shattered glazing, widespread frame deterioration, and skylights that no longer meet current energy codes also point toward a full swap. Timing a replacement alongside a roof replacement avoids disturbing new shingles later.
Common issues
| Symptom | Likely causes | Safe check | Stop when |
|---|---|---|---|
| Water stains on the ceiling or around the skylight frame | Failed sealant, cracked or improperly lapped flashing, damaged underlayment, or clogged weep holes | From inside, trace the stain edges with a flashlight after rain and note whether moisture appears at the frame corners or farther out on the ceiling | Water drips onto electrical fixtures, the ceiling sags, or the drywall feels soft and crumbles to the touch |
| Fog or condensation between the glass panes | A failed insulated glazing seal that lets humid air enter the double-pane cavity | Wipe both glass surfaces from inside and outside to confirm the haze sits between the panes rather than on a surface | The inner pane cracks or moisture pools at the frame base and drips into the room |
| Drafts or noticeable temperature swings near the skylight | Worn weatherstripping on venting models, gaps between the frame and rough opening, or an older single-pane unit | On a windy day, hold a hand or a thin strip of tissue around the interior frame edges to detect moving air | Ice forms on the interior glass or frame during cold weather |
| The venting skylight will not open or close smoothly | A stripped crank gear, bent track, debris in the channel, or a failed motor on electric models | With power disconnected on motorized units, clear visible debris from the track and test the crank gently by hand | The mechanism binds hard, grinding noises occur, or the glass shifts within the frame during movement |
| Cracked, chipped, or shattered skylight glass | Hail impact, falling branches, thermal stress, or installation pressure applied unevenly to the pane | Photograph the damage from the ground with binoculars or from a stable interior position; avoid climbing onto a roof with broken glass | Glass fragments hang loose over living space or the opening is exposed directly to the sky |
| Daylight visible around the frame from the attic | Gaps between the curb and roof deck, deteriorated flashing, or framing that has shifted over time | Enter the attic in daylight, keep weight on joists only, and look upward for pinpoints of light around the frame perimeter | The surrounding decking feels spongy, shows dark water staining, or nearby framing members appear warped |