Why Skylight Leaks Keep Coming Back
The most common skylight leak we see is one that has already been “fixed.” Someone climbed up, ran a bead of caulk around the frame, and it held for a season. Then the freeze-thaw cycle cracked the caulk and the drip came back, usually in February.
Caulk does not fix a skylight leak because the leak is almost never a caulk joint. It is a missing piece of head flashing, step flashing that rusted through, an ice dam pushing water uphill under the shingles, or warm, humid air condensing on cold glass. Leak repair means finding which one and rebuilding that layer.
The 5 Most Common Winter Skylight Leak Sources in Toronto Homes
- Ice dams above the skylight. Attic heat melts snow, it refreezes at the cold curb and backs water under the head flashing.
- Missing or short ice and water shield. Without it, any water that gets past the shingles goes straight to the deck.
- Failed step flashing. Rusted or loose side pieces let wind-driven rain in.
- Reused flashing after a re-roof. New shingles, old skylight flashing, new leak.
- Condensation. Not a roof leak at all, but humid air hitting cold glass and an uninsulated shaft. Nearly half of our January “leak” calls end up here.
Residential Leak Repair
Kitchen Skylights
Steam increases condensation, especially over islands where pot lids come off five times a day. We check the shaft before touching the roof because about half of kitchen “leaks” turn out to be insulation and vapour barrier problems, not flashing, and the fix is half the cost of a re-flash. Honest pricing on this is what most callbacks are about.
Bathroom Skylights
Shower humidity condensing on cold glass is the usual culprit, and the drip shows up long after the shower is off because the cold glass and shaft keep condensing. Venting the unit with a Velux VS or sealing the shaft with Roxul and 6-mil poly fixes it, and the diagnostic visit tells you which one is the actual cause before we quote.
Stairwell and Hallway Skylights
Head flashing and ice dam leaks show up as stains on the uphill side of the shaft because water follows the framing downhill before it shows up on the drywall. Sequenced hose testing from the bottom of the unit up confirms which one is the actual culprit, and the fix is different for each, so we never assume.
Attic Bedrooms
Deep uninsulated shafts drip on cold mornings because warm house air hits the cold glass, condenses and runs down the inside of the shaft. Roxul batt insulation plus a sealed 6-mil poly vapour barrier fixes it for under $700 in most cases, and a venting Velux VS upgrade is the long-term answer if the drip keeps coming back.
Cathedral Ceilings
Low-pitch roofs hold snow longer and need saddle crickets above any skylight wider than about 4 feet so the snow does not drift against the curb and back water under the head flashing. Most cathedral ceiling leaks are ice dam problems that a 24 inch saddled crickit plus extended ice and water shield up-slope fix permanently.
Additions With Flat Roofs
Short curbs and caulked membrane tie-ins are the usual culprits because flat roofs pond water right up against the curb for hours after a storm. We rebuild the curb to a minimum 8 inch height, tie the new membrane in with a manufacturer-approved boot, and add a saddled crickit up-slope so the water has somewhere to go. See flat roof skylights.
Heritage Homes
Slate and copper flashing on Rosedale, Cabbagetown and The Annex houses need careful hand-formed repair because factory kits do not match the existing roof profile. We carry copper stock on the truck for those calls and form step and counter-flashing on site, so the heritage committee paperwork is not held up waiting on a metal shop turnaround.
Commercial Leak Repair
Office Domes
Failed curb sealant and membrane tie-ins, usually on 1990s acrylic domes over office lobbies where the original sealant has finally given up. We cut out the failed sealant, re-tie the membrane to the curb with a manufacturer-approved boot, and reseal with a compatible polyurethane that flexes through Toronto’s freeze-thaw.
Retail Skylights
Repairs scheduled before opening so the sales floor is open by 9 a.m. and the customers never see the crew. Most retail skylight leaks land between $500 and $1,200 with a Velux EDL re-flash and ice and water shield, and we work off the roof access the property manager already has approved.
Warehouses
Ponding at short curbs, especially on TPO and EPDM roofs where the membrane was never lifted up to the new curb height. We re-tie the membrane with a manufacturer-approved boot and, where the structure allows, raise the curb to a minimum 8 inches so water drains away instead of pooling against the skylight.
Condo Amenity Spaces
Board-coordinated repairs with COI on file with the management company and access arranged through the concierge. Condo amenity skylight leaks usually trace to the same failed curb sealant you see everywhere, and we batch the work so the swing-stage only mobilizes once for the whole building.
Specialty Leak Solutions
Saddle Crickets
Divert snow and meltwater around wide skylights so the curb never sits in a drift for the whole month of February. We build the cricket on the uphill side of any unit wider than 4 feet and tie it into the existing shingles or membrane so it sheds water before it has a chance to back up under the head flashing.
Condensation Gutters and Shaft Insulation
Stop drips from humidity by sealing the inside of the shaft with Roxul batt, 6-mil poly vapour barrier and, in the worst cases, a small condensation gutter at the bottom of the shaft to catch any drips before they reach the drywall. This is the fix for about half of our January “leak” calls, and it usually lands between $500 and $900.
Re-Flashing With Factory Kits
Velux EDL for shingles, EDM for metal and EDW for tile or slate, matched to the roofing on your quote so you are not paying for a kit that does not actually fit. Every re-flash gets fresh Grace Ice & Water Shield lapped 18 inches up the curb, and we sign off against our founder’s leak checklist at the end of the day.
Smoke Pencil Tests
Find air leaks around frames that bring humid house air to cold glass, which is the cause of more January “leaks” than most homeowners expect. We hold a smoke pencil at the curb corners while someone watches the shaft inside, and where the smoke pulls we seal with compatible polyurethane so the humid air stays in the room where it belongs.
Materials for Leak Repair
| Problem | Repair materials |
|---|---|
| Ice dam | Grace Ice & Water Shield extended up-slope, saddle cricket |
| Flashing failure | New factory kit or aluminum step and counter-flashing |
| Transitions | Grace Vycor membrane at curb corners |
| Condensation | Roxul batt, 6-mil poly, sealed shaft |
Our Leak Repair Expertise
We have traced thousands of skylight leaks across the GTA. We know the dew point math behind January condensation, the way meltwater travels along a rafter before it shows up two feet from the skylight, and exactly which corner of a 1990s builder install usually fails first. Nine times out of ten, this is where the previous installer cut a corner.
What Actually Stops Homeowners From Fixing a Leak Properly
“It only drips when it’s really cold.”
In our opinion, that is the best clue you can give us because it points to either ice damming at the curb or condensation in the shaft, and the two have completely different fixes. Ice dam leaks need a saddled crickit and extended ice and water shield; condensation leaks need Roxul insulation and a sealed vapour barrier, and we test before we quote so you do not pay for the wrong repair.
“I already paid someone to fix it.”
If it was caulked, it was not fixed, because caulk almost never fixes a skylight leak in our climate. We strip the caulk, run sequenced hose testing and thermal imaging to find the source, and write up the cause in plain language with a CAD price to fix it once. Honestly, caulk is the most expensive way to delay the repair.
“They’ll say I need a new skylight.”
If the unit is sound, we repair it, and we tell people to repair rather than replace on most calls where the unit is under about 20 years old with clear glass. We recommend replacement only when repair will not last ten years, which is a small share of the leak calls we get. Honest pricing on this is what most callbacks are about.
“The ceiling is already stained.”
We can repair the drywall and insulation after the leak is fixed, with a drywall finisher on the truck for repair days where the ceiling has been stained. The interior work is line-itemed on the quote as its own row so the leak fix and the cosmetic repair do not get bundled into one mystery number.
Leak Repair Timeline
First Call
Leak history over the phone, same-day or next-day visit for most of the GTA, with our 24/7 emergency line answered by a person for active storm leaks after hours. When you describe the symptom and the weather, our dispatcher can usually tell you on the phone whether the leak is urgent or can be patched temporarily until the next regular slot.
Diagnostic Visit
Hose testing, thermal imaging, written cause and price. We run sequenced water testing from the bottom of the skylight up with someone watching inside, use infrared cameras to find wet insulation and cold spots, and write up the cause in plain language with a CAD price to fix it before any work starts. Honest pricing on this is what most callbacks are about.
Repair
Usually same visit as the diagnostic if the parts are on the truck and the cause is a flashing or seal issue. The crew lead rebuilds the failed layer with new ice and water shield and a factory flashing kit, signs off against our founder’s leak checklist, and the bucket goes back in the garage before the day is done.
Re-Test and Report
Proof it is dry, photos for your records or insurer. We run a second hose test on the rebuilt zone after the repair, email you the before-and-after photos the same day, and write up a contractor report in plain language that is ready for your insurance adjuster if storm damage is the cause.
Skylight Leak Repair Cost in Toronto: What You Are Paying For
Testing and Diagnosis
The step that saves you from paying twice, because guessing at a skylight leak is the most expensive way to fix one. We test from the bottom of the unit up, image the shaft for wet insulation and cold spots, and put the cause and the CAD price in writing before the crew reaches for a tool.
Flashing Materials
Factory kits (Velux EDL, EDM or EDW) or hand-formed step and counter-flashing for heritage roofs where a kit does not fit. We match the kit to the roofing material on the quote so you are not paying for a flashing detail that does not actually fit your shingles, tile, slate or membrane.
Underlayment
Ice and water shield around the full curb, lapped a minimum 18 inches up the slope so Toronto freeze-thaw and ice damming have nothing to grab. Grace Ice & Water Shield and Grace Vycor at the corners are our standard, never substituted for cheaper synthetics, and we detail to OBC 9.26 for roofing on every repair.
Crickets
Added on wide units and snowy roofs, especially on kitchen additions and cathedral ceilings where the snow load piles against the curb for weeks at a time. A saddled cricket up-slope of the skylight runs $300 to $600 on most repairs and is the single most effective add-on for stopping repeat ice dam leaks.
Shaft Work
Insulation and vapour barrier for condensation, because about half of our January “leak” calls are really shaft condensation rather than a roof leak at all. Roxul batt plus 6-mil poly sealed at every seam is our standard, and a venting upgrade to a Velux VS is the long-term answer for the worst cases.
Interior Repairs
Drywall and paint after the leak is fixed, quoted separately so the leak repair and the cosmetic work do not get bundled into one mystery number. We bring a drywall finisher on leak repair days where the ceiling has been stained, so the room is back to paint-ready before we leave.
Leak Repair vs Replacement vs Installation: Which Service You Need
Sound unit, one leak source: repair. Fogged, old and leaking: residential replacement. Active storm leak right now: emergency service.
Fixed, Venting or Solar: Choosing Your Skylight Type
If condensation is the issue, a venting Velux VS or solar VSS can help by letting humid air out at the ceiling. If replacement is needed, it is the right moment to choose.
Leak Repair Timeline in Toronto: What to Expect Week-by-Week
Most leaks are diagnosed within a day or two of your call and repaired within the week. Winter jobs wait for safe roof conditions, with temporary protection in the meantime.
Why Toronto Homeowners Trust Our Leak Specialists
We have been tracing and fixing skylight leaks across Toronto and the surrounding GTA for over twenty years, certified for both Velux and Fakro since 2004. Every repair starts with sequenced hose testing and thermal imaging instead of a guess and a bead of caulk, every crew is in-house and WSIB-covered with no subcontractors, and every quote lists parts and labour on separate lines with no padding. CSA A440-rated glass, factory flashing and a written workmanship warranty round out what you are actually paying for. We test, we trace and we rebuild. Trust us, you’re in good hands.
