Windows and Glass in Markham: A Homeowner's Guide
Most Markham window problems are glass problems, fixed with new glass in the existing frame: fogged sealed units in the suburban houses and townhouses built since the 1970s, and broken panes in the older sash of the 19th-century village cores in Unionville, Markham Village, Thornhill and Buttonville. In Markham's four heritage districts, repairing a broken pane to original specifications needs no heritage permit, while removing and replacing a window needs a Minor Heritage Permit. Markham also needs about 14% more heating than downtown Toronto by heating degree-days.
Markham grew from about 56,000 people in 1976 to 338,503 in 2021, so most of its houses have factory-sealed double-pane units from the 1980s onward; when one fogs, a new sealed unit goes into the existing frame.
Single-detached houses make up 56% of Markham's dwellings and townhouses 14%; apartments of 5+ storeys rose 28% between 2016 and 2021 and are now about 16% of dwellings.
In Markham's four heritage districts, repairing broken window panes to original specifications doesn't need a heritage permit, but removing and replacing windows or doors needs a Minor Heritage Permit, which has no application fee.
Markham's heritage guidance ranks the options: maintain before repair, repair before restore, restore before replace.
Markham is rated at 4,000 heating degree-days against 3,520 at Toronto City Hall, and has recorded −35.2 °C and 37.8 °C, a wide swing for glass edge seals.
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Markham has two kinds of window stock side by side. Most homes are suburban houses and townhouses built since the 1970s, when the new town's population took off from about 56,000 in 1976 to 338,503 in 2021. But the city also has four 19th-century village cores protected as heritage districts, where repairing a broken pane to original specifications needs no heritage permit but replacing the whole window does.
So a Markham glass job is usually one of two things: a fogged sealed unit in a 1980s–2000s house, or a broken pane in an older sash in Unionville, Markham Village, Thornhill or Buttonville. Either way, the fix is usually new glass in the frame you already have, and Markham makes the heritage case easier than you might expect, as long as the repair matches the original.
How Markham was built, and what that means for its windows
Markham's growth came in a steep curve: 114,597 people in 1986, 153,811 in 1991 and 338,503 in 2021. Today 56% of dwellings are single-detached, 14% are townhouses, 6% semi-detached, 5% duplex and 18% apartments. Apartments of 5+ storeys grew 28% from 2016 to 2021 and make up about 16% of dwellings.
Heritage villages
Unionville's first settlers arrived with William Berczy in 1794, and Main Street still resembles the small town that developed over a century or so starting in the early 1840s, with 19th-century homes along it. Markham Village, Thornhill and Buttonville are the other three districts. Older homes here are more likely to have wood sash and single glazing, so the usual problems are broken panes, loose glazing and worn hardware rather than seal failure.
1960s to 1990s suburbs
Major housing development reached Unionville in the 1960s and is still ongoing. The subdivisions from Markham's 1970s–1990s boom have original sealed units that are now 25 to 45 years old. Sealed-unit life is typically 10 to 25 years, so fogged glass is the most common call in these areas, and a new sealed unit in the existing frame is the usual fix.
Cornell and the newer townhouse stock
Cornell was designed as a new urbanist community in 1994 by Duany Plater-Zyberk, and building began in 1997. Most homes are townhouses, semis or detached houses with garages off rear lanes. These units are younger, but not immune: a 25-year field study found 4.9% of sealed units had failed by year 10 and 7.9% by year 15.
Downtown Markham and the condo towers
Toronto, Vaughan and Markham have had the highest share of new condo development in the Toronto area since 2016. Early Canadian window-wall systems had sealed units that often fogged after only a few years, which led to tighter requirements.
| Where | Typical glazing | Common problems |
|---|---|---|
| Unionville, Markham Village, Thornhill, Buttonville cores | Older wood sash, some single glazing | Broken panes, loose glazing, sash wear (heritage rules apply) |
| 1970s–1990s subdivisions | Original double-pane sealed units, casements, sliders | Fogged units, stripped cranks, patio-door rollers |
| Cornell, South Unionville (1990s–2010s) | Vinyl windows, larger units | Early seal failures, thermal cracks |
| Downtown Markham condos | Window wall, balcony doors | Seal failures; the condo declaration decides who pays |
Markham's heritage exemption for broken panes
This is the rule most Markham homeowners don't know about. Within Markham's four heritage districts, the City lists "Repair of broken window panes to original specifications" as work that does not require a heritage permit. "Removal and replacement of windows or doors" does need a Minor Heritage Permit. Minor Heritage Permits carry no application fee, but they still take time.
Markham's district guidance puts it plainly: "It is better to maintain than to repair. It is better to repair than to restore. It is better to restore than replace".
In practice, that means:
- A cracked or broken pane in an original sash: we replace the glass to match, keeping the sash. No heritage permit is needed under Markham's exemption.
- A fogged sealed unit in a later window within a district: replacing the glass inside the existing frame is closer to repair than replacement. Confirm with Markham heritage staff if the window is visible from the street.
- A failed frame, or a change to the window's look: that's a window-replacement job, not a glass repair, and it needs a Minor Heritage Permit first. We'll tell you if that's where you are.
Markham's climate and your glass
Markham is rated at 4,000 heating degree-days, against 3,520 at Toronto City Hall, about 14% more heating demand. Recorded extremes run from −35.2 °C (January 16, 1994) to 37.8 °C (August 8, 2001).
That swing works the edge seal. Sealants are six to eight times more permeable at 60 °C than at 20 °C, and temperature cycling is one of the main ageing drivers. In winter, colder glass also means more condensation on the room side. NRCan notes that tighter windows can raise indoor humidity, so keep bath and kitchen fans running through the winter. Our condensation guide covers humidity targets.
Permits and condo rules in Markham
Building permits. New glass in an existing frame doesn't change the opening and is generally treated as repair. For whole-window replacement, we couldn't confirm Markham's same-size rule from the City's published guides. Markham's Guide to Building Permits asks for window sizes and egress window details on secondary-suite and coach-house permits, and it points homeowners to the Building Counter for anything unclear. Check with Markham Building Standards before enlarging or adding an opening. Our GTA permit guide compares the rules we could confirm.
Condos and condo townhouses. Ontario's default is that the corporation repairs common elements and owners repair their units, but the declaration can shift that. Check yours before booking.
What we'd do on a Markham job
For a fogged unit in a sound frame, we replace the sealed unit and keep the window. Standard sealed units run $400–650 in the GTA, and oversized ones $900–1,500+. Size, glass type and access all move the price. For heritage sash, we match the original glass so the repair stays within Markham's exemption. If a frame has failed, we'll tell you it's a window-replacement job rather than a glass repair. Not sure which way to go? See our repair vs replacement guide.
Areas of Markham we serve
We cover all of Markham's communities: Unionville (including South Unionville), Markham Village, Cornell, Berczy Village, Milliken, Buttonville, Downtown Markham and the Markham side of Thornhill. We also serve neighbouring Richmond Hill and Scarborough.
Next step
For fogged, cracked or broken glass in a Markham home, see our Markham window repair page and ask for a free quote. If you're in a heritage district, tell us when you get in touch and we'll quote a like-for-like repair.