Why Skylights Leak More in Snow Country
A skylight is essentially a hole cut into the most weather-exposed surface of your home, then sealed back up with glass, metal, and flashing. When everything is installed and maintained correctly, that assembly stays watertight for decades. When any one component fails, water finds the gap.
The Inland Northwest is harder on skylights than most climates. Heavy snow loads sit on the glass and the upslope flashing for weeks at a time. Repeated freeze-thaw cycles work moisture into hairline gaps and then expand it as ice, prying seams open a little wider each winter. Ice dams form at the eaves and around roof penetrations, backing meltwater uphill and under flashing that was only ever designed to shed water flowing downhill. Add wind-driven rain in the shoulder seasons and intense summer UV that bakes sealants brittle, and you have a recipe for leaks that a milder climate would never produce.
The good news: most skylight leaks trace back to a handful of predictable causes, and most are repairable without tearing your roof apart.
It Might Not Be a Leak at All: Condensation
Before you assume the worst, rule out condensation. Skylights are cold surfaces in winter, and when warm, humid indoor air hits the glass it can bead up and run down the frame, mimicking a leak. This is extremely common in Spokane and Coeur d'Alene homes during cold snaps, especially in bathrooms and kitchens.
A few clues point to condensation rather than a true roof leak:
- Water appears on cold, clear mornings rather than during or right after rain or snowmelt.
- The moisture is on the inner glass or the lower edge of the frame, not staining the surrounding drywall or wood.
- It worsens when indoor humidity is high (showers, cooking, drying firewood indoors).
You can cut condensation by running exhaust fans, improving attic ventilation, and confirming the skylight shaft is insulated. If the water is staining the drywall around the opening or dripping after storms, though, it is a genuine leak and worth tracking down.
The Most Common Causes of a True Skylight Leak
When water is actually getting past the assembly, the source is almost always one of these:
- Failed flashing. The metal flashing that ties the skylight curb into the surrounding roof is the single most common failure point. Poorly installed step flashing, missing head flashing, or flashing that was caulked instead of properly woven into the shingles will eventually leak, especially under snow and ice loading.
- Degraded sealant. The factory and field-applied sealants around the glass and frame dry out, crack, and shrink after years of UV and temperature swings. Once they fail, the glass-to-frame joint is exposed.
- Worn gaskets or a failed seal between panes. On older units, the rubber gaskets harden and the insulated glass unit can lose its seal, leading to fogging between panes and moisture intrusion.
- Cracked or damaged glazing. Hail and falling branches can crack the dome or glass outright.
- Ice dam backup. Even a perfectly sealed skylight can leak if an ice dam forces water uphill and under the head flashing.
- Age. Most skylights last roughly 15 to 25 years. Past that, seals and flashing are simply at the end of their service life.
How to Find Where the Water Is Getting In
Finding the true entry point matters because water travels. A stain on the drywall directly below the skylight does not mean the leak is right there. Water can enter at the upslope flashing, run down the framing, and emerge feet away.
From inside, note exactly where the water shows up and under what conditions. A leak that only appears during wind-driven rain points to flashing or sealant on the windward side. A leak that shows up during a midwinter thaw, with no rain, strongly suggests an ice dam.
From outside, the area to inspect is the head (upslope) flashing first, since that takes the most water and snow, followed by the side step flashing and the sealant beads around the glass. Look for lifted shingles, cracked caulk, separated metal seams, and any spot where someone has globbed on roofing tar as a past 'fix.'
Walking a snowy or steep Inland Northwest roof is genuinely dangerous, and it is easy to misread a leak's source. If you are not certain, a professional inspection is the safer call. DG Contracting offers free estimates and can pinpoint the entry point without guesswork.
Repair Options, From Simple to Full Replacement
The right fix depends on what failed and how old the skylight is.
Re-sealing and minor sealant work
If the flashing is sound and only the surface sealant has cracked, cleaning out the old material and re-applying a high-quality roofing sealant can buy years. This is the least invasive option but only works when sealant is the true problem, not flashing.
Re-flashing the skylight
When the flashing has failed, the correct repair is to lift the surrounding shingles and install a proper flashing kit, woven into the courses with head, side, and apron pieces. Many manufacturers sell flashing kits matched to the unit. This addresses the most common leak cause at the root rather than masking it with caulk.
Glass or gasket replacement
A cracked pane or a fogged, seal-failed insulated glass unit can sometimes be replaced without swapping the whole skylight, depending on the brand.
Full skylight replacement
If the unit is past 20 years, the seals are gone, or the frame is rotting, replacement is usually the smarter long-term value. The best time to do it is during a roof replacement, when the surrounding roofing is already open and the new skylight, flashing, and shingles can all be integrated as one watertight system.
Why Proper Flashing and Installation Matter So Much Here
Most skylight leaks we see in the Spokane and North Idaho area are not product failures. They are installation failures, almost always a flashing shortcut. Caulk is not flashing. A bead of sealant relied on as the primary water barrier will fail within a few seasons of freeze-thaw, while a properly woven metal flashing system relies on gravity and overlap to shed water and lasts the life of the roof.
This is also why the quality of the roofer matters. As a GAF Master Elite contractor, a certification held by only a small fraction of roofers nationwide, DG Contracting installs skylights and their flashing to manufacturer specifications, which is what keeps the workmanship and material warranties intact. Our work is backed by a 15-25 year workmanship warranty alongside the GAF Golden Pledge coverage.
If you are weighing a more durable roof overall, metal roofing sheds snow and resists ice dams well, and skylight flashing details can be integrated cleanly into a standing-seam system.
Preventing the Next Leak
A little maintenance goes a long way in this climate:
- Inspect annually, ideally in early fall before the snow flies, checking flashing seams and sealant.
- Keep the upslope side clear. Don't let leaves, needles, and debris dam up against the head flashing where they trap moisture.
- Address ice dams at the source with adequate attic insulation and ventilation so the roof stays cold and snow doesn't melt-refreeze at the edges.
- Don't let small problems sit. A cracked bead of caulk is cheap to fix; the rotted framing and ruined drywall it eventually causes are not.
- Use a qualified roofer for any flashing work so the repair is done right the first time.
Caught early, a skylight leak is a minor repair. Ignored through a couple of Inland Northwest winters, it can mean mold, rotted sheathing, and interior damage. If you've spotted a stain or a drip, get it looked at before the next freeze-thaw cycle makes it worse.