Roof Repair in Thornhill
Brittle flat sections over garages, shingles past a first cycle, flashing at additions that were built quickly. We trace Thornhill leaks and repair the cause.
Roof Repair in Thornhill, what we fix.
Roof leak repairs
Emergency tarping
Storm damage repair
Shingle repairs & replacement
Metal roofing
Flat roof repairs (EPDM, TPO, Mod-Bit)
Why Blue Knight finds it when others don't.
We trace first
Written reports
25+ years experience
No upsells
60-min emergency
Permanent repairs
We trace first
Every job starts with a full trace from interior stain back to the roof. We find the source before touching anything.
Written reports
You receive a written diagnostic report with photos, suitable for insurance, lenders, and property management files.
25+ years experience
Two and a half decades on GTA roofs means we've seen every failure mode across every building type in the region.
No upsells
We don't sell replacements when repairs are appropriate. Our invoice reflects what the building actually needs.
60-min emergency
Active leaks get same-day priority dispatch, around the clock, including nights and weekends.
Permanent repairs
We use manufacturer-matched materials and test the repair before we leave. No waiting for the next rain.
“We trace the leak from the stain back to the source. That's how leaks get fixed permanently.”
“We trace the leak from the stain back to the source. That's how leaks get fixed permanently.”
Rated 5 out of 5Blue Knight was, by far, the best. Responsive, ethical, totally professional — and their crew went above and beyond at no extra charge.
Rated 5 out of 5They installed a full new roof in one day. The crew worked around the house without us hardly knowing they were there.
Rated 5 out of 5I emailed at 4 a.m. and spoke with someone that same day. Estimate and completed work all within one day. Pricing was fair, work was excellent.
Blue Knight was, by far, the best. Responsive, ethical, totally professional — and their crew went above and beyond at no extra charge.
They installed a full new roof in one day. The crew worked around the house without us hardly knowing they were there.
I emailed at 4 a.m. and spoke with someone that same day. Estimate and completed work all within one day. Pricing was fair, work was excellent.
Luciano did not try to sell me a new roof. Appreciated the honesty — he showed up when he said he would.
We had a leak diagnosed by two other contractors who could not find the source. Blue Knight found it on the first visit and fixed it the same week.
Flat roof replacement on a commercial unit. Clean, fast, no surprises on the invoice. The crew left the site cleaner than they found it.
Called after a storm damaged our roof. Someone was on site within hours, tarped everything, and had us fully repaired before the next rain.
Had a slow basement leak for years. Every other company just caulked it. Blue Knight found the actual source and did a proper waterproofing job. No issues since.
Our neighbours recommended them for a valley repair. Small job, but they treated it like it mattered — showed up on time, matched the shingles perfectly, and charged exactly what they quoted.
Our Work.
Rooftops across the GTA.
From downtown Toronto to the 905 and beyond, one crew, one warranty, twenty-five years of GTA rooflines.
Service availability may vary. Call (647) 383-8664 to confirm coverage for your area.
Rooftops across the GTA.
From downtown Toronto to the 905 and beyond, one crew, one warranty, twenty-five years of GTA rooflines.
Service availability may vary. Call (647) 383-8664 to confirm coverage for your area.
Roof Repair questions for Thornhill.
Localized repairs run $350 to $2,000 depending on the failure and the access. A flat section membrane repair over a garage typically sits in the lower half of that range unless ponding has undermined a larger area. Full replacement on a typical Thornhill home runs $9,000 to $22,000.
Usually because there is not enough fall for it to drain, so water sits on the membrane rather than running off it. Any patch on a ponding roof is temporary. Where that is the situation the honest answer is that the slope has to be built before a membrane will hold, and we say that rather than selling another repair we expect to fail.
Sometimes, and it depends what you are buying with the money. A repair that carries a sound roof another five or eight years is good value, while a repair on a roof with two years left is deferring the replacement at extra cost. We open a section and tell you which of those you are looking at rather than guessing from the age.
Always, itemized and after the diagnosis rather than before it. The estimate names what failed and what the repair involves, so you can compare it against another proposal on substance rather than on the total at the bottom.
Yes, on every job as standard. The report includes dated photographs of the condition before and after, the failure described by mechanism, and the materials used. That record settles the sudden versus gradual question an adjuster will ask, and it answers a buyer's inspector at resale.
Flat section membranes at seams and wall junctions, followed by ordinary end of life failures on the sloped shingles, followed by flashing at additions that were built after the original house and tied in quickly. Knowing that order is why our diagnosis is fast.
Usually not, because on these houses the failure is nearly always the curb flashing around the unit rather than the glazing or the seal, which makes it a flashing repair rather than a skylight replacement. Step flashing up the sides, a proper head flashing above, and an apron below all have to be layered into the covering, and the common shortcut was to bed the whole assembly in sealant instead. We diagnose the curb before anybody quotes you a new unit, because replacing the skylight and reusing the same detail reproduces the same leak.
Orientation and exposure: the slope facing the prevailing weather takes the wind and driving rain, and the south or west facing slope takes far more ultraviolet and heat cycling than the one opposite. It is completely normal on a Thornhill house to find one elevation at end of life and another with several years left. That also means a quote based on the worst slope may be replacing more than the building needs, which is why we report condition by elevation rather than as one figure.
Worth establishing, because two is the practical limit and a number of these houses are already there after a first re-cover. If yours is carrying two, the next replacement is a strip to the deck rather than an overlay, which costs more, needs budgeting for, and exposes sheathing nobody has seen since the overlay went on. We check at the rake and eave edges during diagnosis and tell you where you stand.
At the eaves and in the valleys, yes, and on a good deal of this housing it either was not or it was run too short to be useful. That membrane is what protects the assembly when meltwater backs up behind an ice dam, and its absence is the reason some Thornhill roofs leak every February despite sound shingles. It can only be added when the covering comes off, so it is a replacement item rather than a repair, and we will tell you whether yours has it.
Roof repair in Thornhill divides between the sloped roof and the flat section, and they are different trades. On the sloped roof the housing is at or past a first full cycle, so the failures are the ordinary end of life ones: sealant strips gone, nail line working loose, pipe boots cracked, and wind loss on whichever slope takes the weather.
The flat sections are where the surprises live. Early modified bitumen and EPDM over garages and rear additions has gone brittle after three decades, and it fails at seams and at the junction where the flat meets the wall of the house. A roofer who only does slope will patch that with sealant and be back next spring.
The Edge of the Roof Does More Work Than the Middle
The eave is where a Thornhill roof is most likely to be quietly failing, and it is the part almost nobody looks at. Water concentrates there, ice forms there, and the assembly at that edge is a stack of components that each depend on the one behind them: the shingle course, the drip edge, the fascia board, the eavestrough, and the soffit with its intake vents.
When the eavestrough has been overflowing for a few seasons, either from debris or from a pitch that has dropped, the water runs behind it instead of through it. That saturates the fascia board and the ends of the rafters it is fixed to, and because it is happening behind aluminium capping there is nothing to see from the ground. We check the fascia by probe rather than by eye for exactly this reason, and on a house of this age we find soft timber behind sound looking capping fairly regularly.
It matters at quoting time because rotten fascia is not a roofing extra to be discovered mid-job. Fasteners will not hold in it, so the drip edge and the trough have nothing to fix to, and a covering installed over it is compromised at its most exposed edge. We report it before the work rather than after the tear off.
Skylights, Boots, and Everything That Punctures the Roof
Every hole in a roof is a managed failure waiting to happen, and on Thornhill's housing the penetrations are where a disproportionate share of the leaks originate. Plumbing stack boots crack at the rubber collar after twenty to thirty years of ultraviolet exposure, which is entirely predictable and cheap to correct. Bathroom and range vents lose their flashing seal. Skylight curbs, which are the largest penetration on most of these houses, fail at the flashing rather than at the glass.
The reason this matters commercially is that a penetration failure and an end of life covering look identical from inside the house. Both produce a ceiling stain. One is a few hundred dollars and one is a replacement, and the only way to know which you have is for somebody to go up and look at the detail rather than at the age of the roof.
We report penetrations as their own line items with their own recommendations, so a sound roof with three cracked boots gets three boots rather than a replacement quote.
The Flat Section Nobody Quotes Properly
A great many Thornhill houses are not entirely sloped. The subdivisions of the 1980s and 90s frequently put a flat or near flat roof over a garage, a rear addition, or a porch, and thirty years on that is the part of the building most likely to be leaking.
It matters because it needs a different trade and a different quote. Membrane work is not shingle work, and a roofing quote that treats the flat section as an afterthought is a quote that will need revisiting. We price it separately and explain what we found, including the awkward answer when the problem is drainage rather than the membrane.
Repair or Replace on a Thirty Year Old Roof
Most Thornhill owners at this point have been told by somebody that the roof needs replacing. Often that is right. Frequently it is a conclusion reached from a driveway on a roof that has eight good years left in the field and one failed detail.
We open a section before recommending replacement, photograph the deck, and put the finding in writing. If the roof is finished, the photographs show why. If it is not, you have evidence to hold up the next time somebody knocks on the door after a storm.
We also cover nearby cities.
Ready to schedule your estimate?
We come to you, assess the roof, and give you a written quote. You are not obliged to proceed. Most estimates completed same week.