There's a reason skylights show up on so many renovation wish lists, a room with one just feels different. More light, less reliance on lamps during the day, sometimes a whole new sense of space in a room that used to feel closed in. But we've also spent years fixing skylights that were put in badly, and it's rarely the product's fault. It's almost always how, and where, it was installed. So before you call a contractor, here's the stuff worth knowing first.
What Does a Skylight Actually Cost in the GTA?
For a typical residential job, expect somewhere between $1,200 and $3,500 per unit, materials and labour included. That's a wide range, and a few things push it up or down:
- Fixed vs. venting. A fixed skylight just lets light in. A venting one opens, which is nice for a stuffy bathroom or kitchen, but it costs more and has more parts that can eventually need maintenance.
- What kind of roof you have. Cutting into a flat roof isn't the same job as cutting into a sloped shingle roof; different flashing, different labour time.
- Whether framing needs to change. If the skylight doesn't fit neatly between your existing rafters, you're paying for structural work too, not just the window.
- How hard the roof is to get on. Steep pitch, third storey, tricky access; all of that adds time and safety gear.
If a full-size skylight is more than the room (or the budget) needs, tubular skylights are worth a look. They're smaller, tunnel-style units that run more like $600–$1,200, and they're a good fit for hallways, closets, or a small bathroom that just needs some daylight.
Where Should It Actually Go?
This is the part people underestimate. Placement decides whether a skylight is trouble-free for the next twenty years or a recurring headache.
South-facing roof slopes bring in the most light, all day long, but that also means more heat coming through in July and August. If the room already runs warm, it's worth pairing that with tinted or low-E glass so you're not baking the space. North-facing slopes give you softer, steadier light without as much heat, which tends to work well over a kitchen or a home office where you don't want glare.
Structurally, a skylight should sit between rafters, not fighting them, and it needs to stay clear of valleys, ridgelines, or any spot where water already tends to pool or run hard during a storm. If your roof has had ice damming in past winters, that's a sign the flashing height and underlayment need extra attention before anyone cuts a hole in it. And if you've noticed drainage or leak issues already, we go over the warning signs in our piece on common causes of roof leaks, get that sorted first. Adding a new penetration to a roof that's already struggling is asking for trouble.
The Mistakes We See Over and Over
Honestly, we get called out for skylight repairs more than we get hired for new installs, and it's usually one of the same handful of problems:
Flashing done wrong, or done cheap. This is the big one. Flashing has to be layered properly with the shingles or membrane, not just caulked around the edges and called finished. Caulk is a stopgap. It's not flashing.
A skylight sized wrong for the rafter bay. Cutting into the framing without accounting for support can weaken the roof deck, and that's not something you notice until years later.
Underlayment that got skipped, or half-done. In older homes especially, not putting proper ice-and-water shield around the skylight curb is asking for leaks come freeze-thaw season, and in Ontario, that's a long season.
DIY installs, or installers who don't do this often. A skylight looks straightforward from the ground. It isn't. One small gap in the flashing can leak quietly into the attic for a year or two before anyone notices water stains.
Ignoring the inside finish. The drywall shaft and insulation around a skylight need to be sealed properly too. Skip that, and you get condensation dripping down, which homeowners almost always assume is a roof leak, when really it's moisture trapped inside the shaft.
If You're Already Planning a New Roof
If your roof is coming up for replacement anyway, this is the cheapest time to add a skylight. The flashing goes in as part of the new roofing system instead of being tied into shingles that are already ten years old. No disturbing a roof you just paid to finish. If that's where you're at, our guide to roof replacement in Ontario is worth reading alongside this one; the two projects overlap more than people expect.
A Few Quick Questions We Get
Do skylights leak more than the rest of the roof? Not if they're put in right. Almost every skylight leak we've traced back comes down to the flashing or underlayment, not a fault in the skylight itself.
How long does the install take? One day for a single fixed skylight going into an existing roof, in most cases. Add framing changes or more than one unit, and you're looking at two or three days.
Can you put a skylight in a flat roof? Yes, but it's a different flashing and curb setup than a sloped shingle roof, and it really should go to someone who works with flat roof membranes regularly, not just asphalt shingles.
Thinking About a Skylight?
The product matters less than who's putting it in. Our skylight repair and installation team has been installing and repairing skylights since 1998, cleaning up installs that went wrong and doing new ones the right way the first time. If you're weighing a skylight, or just want someone to look at one that's already leaking, reach out for a free estimate; we'll get up on the roof with you before anything gets cut.
Get Your Free Roof Estimate
Ready to protect your home? Ontario Tech Roofing has served homeowners across the GTA since 1998. Book your free estimate or call us at 905-616-4408.