The phone starts ringing about skylight repair Markham homeowners have been putting off within a day or two of the first long autumn rain. A damp patch appears at the corner of the ceiling, a drip lands on the landing carpet, or the drywall around the shaft turns a shade darker than it was in August. The frustrating part is that a great many of those calls are not leaks at all. They are condensation, and a contractor who cannot tell the two apart will happily sell you a repair that does nothing.

This guide shows you how to read the symptoms yourself, explains the four places skylights genuinely leak, sets out what repairs cost in 2026, and gives you a clear line between a repair that is worth doing this autumn and a unit that should simply be replaced.

Why Skylight Repair Markham Calls Cluster In Early Autumn

September and October deliver the first sustained rain of the season, and sustained is the key word. A summer thunderstorm passes in twenty minutes and a marginal flashing detail often survives it. Six hours of steady rain driven by an east wind is a completely different test, and it is the test that exposes every shortcut in a roof detail. That is why skylight repair Markham enquiries arrive in clusters rather than evenly through the year.

The second factor is temperature. Once night time temperatures drop into single digits while the house is still warm and humid from cooking, showering and laundry, the inside face of a skylight becomes the coldest surface in the room. Moisture condenses there and runs down onto the shaft. It looks like a leak, it stains like a leak, and it is not a leak.

Booking skylight repair Markham work early in the season matters for a third, practical reason. Shingles are still warm and pliable in September and October, so they can be lifted and reseated around a skylight without cracking, and flashing cements cure properly at daytime temperatures in the low teens and above. A repair done now is a proper repair rather than a temporary patch.

Condensation Or A Genuine Leak? How To Tell

Before you call anyone about skylight repair Markham service, spend ten minutes observing. The pattern of the moisture usually gives the answer, and knowing it makes you a much better customer.

There is a third possibility that sits between the two: a failed insulated glass seal. If the haze or the droplets are trapped between the panes rather than on the inside surface, the glazing unit itself has failed. No repair will fix that, because on residential skylights the glass and frame are supplied as one sealed factory assembly. That case moves straight to replacement.

The Four Places Skylights Actually Leak

When water really is getting in, it is nearly always through one of four details, and every skylight repair Markham diagnosis starts by narrowing it down to one of them. Diagnosing which one saves a great deal of money.

• The head flashing. Water running down the roof above the unit has to be diverted around it. If the head piece was face nailed and caulked instead of being lapped under the shingle course above, it will eventually let water through. On roofs with a long run above the skylight, a saddle or cricket may be required rather than optional.
• The side or step flashing. Each piece must lap the one below and tuck under the shingle beside it. Installations that rely on a continuous bead of sealant instead of layered metal are on borrowed time from day one.
• The sill or apron at the bottom. Less common, but a bent or corroded apron will hold water against the frame instead of shedding it onto the roof.
• The unit perimeter gasket. The gasket between the glazing and the frame hardens with age. On older units it can shrink away from the corners and admit water even though the flashing is sound.

There is a fifth source that is not the skylight at all: a bathroom exhaust fan discharging into the attic rather than outdoors. That dumps warm, moist air directly beneath the roof deck, and the moisture finds the coldest surface available, which is usually the skylight. We check for this on every skylight repair Markham inspection because it explains a surprising number of stubborn cases.

Repairs Worth Doing, And Repairs That Waste Money

Not every repair is a good investment, and the honest split for skylight repair Markham projects looks like this.

Worth doing. Re-flashing a sound unit properly, replacing a corroded apron or head piece, rebuilding a soft section of roof deck around the opening, replacing a hardened perimeter gasket where the manufacturer still supplies one, air sealing and insulating the interior shaft, and re-routing a bathroom fan duct to discharge outdoors. Each of these fixes a specific cause and the result lasts.

Not worth doing. Running another bead of sealant over an existing bead. Applying roof cement across the head of a skylight. Repairing a unit whose glazing seal has already failed. Re-flashing a twenty five year old acrylic dome that is yellowed and crazed. In each of these cases you are paying for access to a component that will fail again soon, and paying for that access twice is the most expensive way to own a skylight.

The test we apply on a skylight repair Markham visit is simple: if the frame and the glazing are sound and only the water management is wrong, repair is the right answer. If the unit itself is compromised, repairing around it is throwing good money after bad.

Skylight Repair Markham Costs In 2026

Repair pricing depends on what is actually wrong, how high and how steep the roof is, and whether interior finishes need attention afterwards. The ranges below reflect typical 2026 residential pricing in the Greater Toronto Area.

A useful rule: once the combined repair cost approaches roughly half the installed price of a new unit, replacement is usually the better value, because a new skylight resets the warranty clock on both the product and the workmanship. Most single unit replacements on a shingle roof run from $1,600 to $4,800 installed depending on whether the unit is fixed, venting or solar powered.

Be cautious about very low quotes for skylight repair Markham work. In our experience they usually cover sealant applied from a ladder and nothing else, which buys a few weeks and leaves the underlying detail untouched.

Markham Housing And What Shows Up On Its Roofs

Markham spans a wide range of building ages, and the pattern of skylight repair Markham requests follows it closely. Older homes in Unionville and Markham Village, and the mature areas bordering Thornhill, often carry original acrylic dome units on site built timber curbs. Those curbs were rarely flashed the way a modern kit flashes, and the acrylic itself has usually gone brittle with ultraviolet exposure, so these are replacement candidates more often than repair candidates.

The large subdivisions built through the 1990s and 2000s, including communities such as Wismer, Berczy and Cornell, tend to have glass units over stairwells, ensuites and family rooms on steeply pitched roofs. Units from that era are now at or near the end of their seal life, and complex roof geometry means many of them sit close to a valley or a dormer, where flashing has to be detailed carefully. Newer homes still have serviceable units, so here a targeted repair is frequently the right answer.

Because the housing is so varied, a phone quote is guesswork. We look at the roof, the flashing assembly, the deck condition and the interior shaft before recommending anything. You can read more about how we handle skylight installation and repair across Markham, and our dedicated skylight repairs page explains what a standard service visit covers.

What A Proper Repair Visit Includes

A serious skylight repair Markham appointment follows a sequence, and you are entitled to see each step reflected in the invoice.

• Interior assessment first. The technician looks at the stain pattern, checks the shaft for air leakage, and notes whether the glazing shows internal moisture. This is what separates condensation from a leak.
• Attic check where accessible. Wet insulation, stained sheathing and a bathroom fan venting into the attic are all found from inside, not from the roof.
• Roof inspection. Shingle courses at the head of the unit are lifted to see how the flashing was assembled. The deck around the curb is pressed for softness. Fasteners, sealant beads and corrosion are recorded.
• Controlled water test. Water is applied in stages from the bottom up so the entry point can be isolated rather than guessed.
• The repair itself. Flashing is rebuilt in layers from the bottom up, deck repairs are made where required, and sealant is used only as a secondary defence, never as the primary one.
• Re-test and report. The completed detail is tested again, and you receive photographs of what was found and what was done.

Most repairs are completed in a single visit of three to six hours. Interior drywall and paint, where needed, are scheduled afterwards so the patch can dry properly first.

When Repair Stops Making Sense

There is a point where continuing with skylight repair Markham work becomes the expensive choice. The table below is the framework our estimators use.

If replacement is the answer, autumn remains a good time to do it. The work is a single day for most units, the weather still suits flashing, and the job is finished before the wettest stretch of the season.

Preventive Steps Before The Wet Part Of The Season

A few straightforward measures reduce the chance of needing skylight repair Markham service at all, and several cost nothing.

Have leaf litter cleared from the roof and the flashing. Mature trees are common in the older parts of Markham, and leaves that pile against the head of a skylight hold water where it should be running away. Having them cleared is the highest value autumn task on any roof with a skylight.

Keep gutters and downpipes flowing. Water backing up at the eave affects the whole roof surface and puts more volume across low details.

Run the bathroom fan for longer. Twenty minutes after a shower rather than five makes a measurable difference to condensation on cool mornings, and it costs nothing.

Confirm the fan actually vents outdoors. If the duct terminates in the attic, no amount of skylight work will solve the moisture problem.

Book an inspection rather than waiting for a stain. A short assessment in early autumn is far cheaper than emergency skylight repair Markham service after water has reached the drywall. Toronto Skylight Installers carries out inspections throughout the Greater Toronto Area and will tell you plainly when nothing needs doing.

Book Skylight Repair Markham Homeowners Can Rely On

If a ceiling stain has appeared, a corner is damp or the glass has gone permanently hazy, a proper diagnostic visit will tell you what is actually happening rather than what is easiest to sell. Toronto Skylight Installers handles skylight repair Markham projects with an interior assessment, an attic check, a roof inspection and a controlled water test before any work begins, and provides photographs of what was found.

Call us today at (416) 365-7557 or request a free consultation before the wettest part of the season arrives.

Proudly serving Markham and communities across the Greater Toronto Area.