Thornlea, Markham — a realtor's guide to the detached-house neighbourhood south of the 407 and west of the 404

Thornlea is a predominantly residential neighbourhood in west Markham, south of the 407 and west of the 404. TRREB draws it between the German Mills Creek valley and Highway 404, with CN's York Subdivision freight line as its southern edge. It covers about three square kilometres; Leslie Street runs through the middle from south to north, and Green Lane enters across the valley in the south-west and ends at Leslie.

The 2021 Census tract that matches it almost exactly (CT 0402.13) shows a very uniform place:

• Almost every home is a detached house. Of 1,565 occupied dwellings, 1,530 were single-detached, with no townhouses, semis or apartment units.
• The housing is mostly of one period. About 81% of homes were built between 1981 and 1990, and the census records none built after 2005.
• There are no shops inside the community. Groceries and errands mean Highway 7 north of the 407, John Street and Bayview south of the rail line, or Steeles at the 404.
• A hydro corridor crosses the north side, and St. Robert Catholic High School sits between it and the 407.

One trap in the name: Thornlea Secondary School (8075 Bayview Ave) and Thornlea Pool (8079 Bayview Ave) are on Bayview, west of the creek valley, and outside TRREB's Thornlea. This page covers the TRREB community only.

On TRREB's community map, checked point by point against OpenStreetMap's road, rail and stream geometry (median offset 3 to 4 metres on the rail and creek edges, about 15 to 18 metres on the highways):

• North: Highway 407.
• East: Highway 404.
• South: CN's York Subdivision rail line. The stretch of John Street facing Thornlea's southern edge runs south of the tracks and is not the boundary; both sides of that stretch are German Mills.
• West: the German Mills Creek valley. Between the creek and Bayview Avenue is Aileen-Willowbrook.

Neighbours: across the 407 to the north, Commerce Valley; across the 404 to the east, Milliken Mills West; across the rail line to the south, German Mills, with Bayview Fairway-Bayview Country Club Estates at the south-west corner; across the creek to the west, Aileen-Willowbrook.

For a particular house, what decides it is whether the address is north or south of the rail line and east or west of the creek. The TRREB community label on the listing is the final word.

The 2021 Census does not report by TRREB community. This section uses census tract 0402.13, which covers 99.9% of Thornlea and lies 94.4% inside it; the extra is mostly a narrow strip along the 407. The tract and the community almost coincide, but these are still tract figures rather than an official count for the community.

• 1,565 occupied private dwellings: 1,530 single-detached houses (97.8%) and 35 units counted as an "apartment or flat in a duplex" (2.2%), with no semis, townhouses or apartment-building units. A detached house with a separate suite can be counted by the census as two duplex units, so by building, nearly everything here is a detached house.
• Bedrooms: 1,425 homes (91%) have four or more; 130 have three.
• Condominium tenure: only 20 homes (1.3%), against 21% across Markham.
• Period of construction: 1,270 homes (about 81%) were built in 1981–90, 145 in 1961–80, 110 in 1991–2000, 30 in 2001–05 and 10 in 1960 or earlier; none after 2005.

Two cautions. Dwelling type and construction period are separate census tables, so they cannot be combined into a claim such as "80% of the detached houses date from the 1980s". And lots backing onto the 404, the 407, the hydro corridor or the rail line may live and price differently from lots on the creek or on inner streets; this page has no data on that.

On 2026-10-23, real house numbers inside the community were run one by one through the YRDSB school locator: 175 addresses on 39 streets, 161 of which returned a result. Here is what came back.

YRDSB regular elementary, split by Leslie Street:

• West of Leslie (25 streets, including Huntington Park Dr, Bronte Rd, Bradgate Dr, Prince Edward Blvd and the Thornlea stretch of Green Lane): Bayview Glen PS (42 Limcombe Dr) for JK to grade 6, then German Mills PS (61 Simonston Blvd) for grades 7 and 8.
• East of Leslie (13 streets, including Lyndhurst Dr, Summerdale Dr, Valleyview Rd and Mowatt Ct): Bayview Fairways PS (255 Bayview Fairways Dr) from JK through grade 8.

No sampled address broke the pattern, and the start, middle and end of each long street agreed; but this is a generalisation from a sample, so check the exact address.

The same for every address that returned a result:

• French Immersion elementary: Woodland PS (grades 1–8, 120 Royal Orchard Blvd).
• Regular and French Immersion secondary: both Thornlea SS (8075 Bayview Ave), for both 2026–27 and 2027–28.
• Programmes by application: the arts programme points to Westmount CI; the IB programme points to Alexander Mackenzie HS for 2026–27, while the 2027–28 lookup returns Langstaff SS. Students apply in grade 8 for entry in grade 9, so the result that matters is the one for the year of entry: a student in grade 8 now, starting grade 9 in September 2027, falls under the 2027–28 result. Langstaff SS is an IB candidate school still seeking authorization and describes its 2027–28 intake as anticipated, so confirm with YRDSB and the school before applying.

YCDSB (Catholic), identical at 21 points across the community: St. René Goupil-St. Luke (135 Green Lane) for elementary, St. Anthony for French Immersion elementary, and St. Robert CHS (8101 Leslie St, inside the community) for secondary. YCDSB's "Additional FI Service Area" layer returns Our Lady Queen of the World in Richmond Hill for French Immersion secondary; that layer may not appear on the public locator page, so confirm with YCDSB.

On location: every YRDSB school returned is outside the community (Bayview Glen, German Mills and Bayview Fairways south of the rail line, Thornlea SS on Bayview west of the valley). On the two boards' data and OpenStreetMap, the only school inside Thornlea is the Catholic St. Robert CHS. Walking distances and bus eligibility have not been checked.

Again from census tract 0402.13. Because a single tract covers the community, its medians can be quoted directly.

• Population: 4,734 in 2021, down about 4.7% from 4,965 in 2016, a period in which the census records no new homes.
• Age: a median age of 50.8, against 42.4 for Markham as a whole; 1,385 residents (about 29%) were 65 or older and about 13% were 14 or younger.
• Households: 3.0 people on average; 100 one-person households (6.4%) and 210 of five or more (13.4%).
• Renters: 55 households, about 3.5%, against about 18% across Markham.
• Income: a 2020 median total household income of $150,000, against $104,000 for Markham. 2020 was a pandemic year, and the figures include government benefits paid that year.
• Commuting: in the May 2021 census, about 90% of commuters went by car, truck or van (935 drivers and 80 passengers) and about 6% by transit. But 955 people worked from home, close to the number commuting, so treat these shares as indicative only.

For Thornlea real estate, TRREB's Q1 2026 Markham community report (All Home Types) shows 4 sales, a median of $1,375,000, an average of $1,576,250, SP/LP of 95% and 105 average days on market.

Before reading anything into these figures:

• The sample is very small. Thornlea records anywhere from a few sales to about a dozen a quarter, so the median, the average and days on market all swing with individual sales. Do not read a trend into one quarter's change from the last.
• "All home types" here effectively means detached houses. In the property-type charts of TRREB's Q1 and Q2 2026 reports, every Thornlea sale and every new listing in both quarters was a detached house; semis, townhouses and condos were zero.
• Compare houses, not averages. Among 1980s detached houses, lot size, orientation, whether the lot backs onto the creek or a main road, and the level of renovation all move the price. For a specific home, pull comparable sales from the last six to twelve months one by one, and where needed add same-era detached sales from neighbouring communities, clearly marked as not Thornlea.

TRREB does not publish rents by community; its rental report stops at the municipal level. For Q1 2026, TRREB's Markham-wide average rents on completed leases were $2,245 for a one-bedroom apartment (333 leases), $2,801 for a two-bedroom apartment (227 leases) and $3,080 for a three-bedroom townhouse (29 leases). These describe apartments and townhouses across all of Markham. They are not Thornlea figures, and they say nothing about the detached houses that make up almost all of Thornlea.

Local listings. On 2026-10-23, Zolo showed five live rental listings tagged Thornlea. Only two could be confirmed as whole houses; the rest were a basement, a main-and-upper lease and a separate suite. That is far too few for a range, so this page gives no local rent range.

The census points the same way: only about 3.5% of households rented in 2021. For any real numbers, pull Thornlea's leased whole-house listings from the last six to twelve months in TRREB's system and group them by bedroom count, rather than relying on asking rents; expect very few.

GO trains. There is no GO station in the community and no passenger line through it; the line along its southern edge is a CN freight route. The nearest stations are on the Richmond Hill line: Langstaff GO, about 1.8 km from the boundary in a straight line to the west, past the creek valley and Bayview, and Old Cummer GO, about 3.2 km to the south. Under Metrolinx Table 61 (effective April 25, 2026):

• The Richmond Hill line runs trains only in the weekday peak direction: four southbound in the morning, leaving Langstaff between 06:15 and 08:16 and reaching Union in 44 minutes (36 minutes from Old Cummer), and five northbound in the late afternoon, leaving Union between 15:45 and 18:45.
• Outside those trains, GO bus route 61 serves Langstaff (not Old Cummer) on a limited timetable: southbound, one early bus at 05:30 and then hourly from 09:46 to 13:48, with nothing southbound after that; northbound buses run from midday, the last reaching Langstaff at 02:07. There is no service on this line at weekends or on holidays.

YRT (service data from September 6, 2026):

• 3 Thornhill runs along Green Lane and Leslie Street between the TTC's Pioneer Village station and the Shops on Steeles and 404, every day.
• 90 Leslie runs the length of Leslie Street through the community, south to the TTC's Don Mills station, every day; 90B follows Leslie on weekdays only.
• 82 Valleymede runs on weekdays only and stops inside the community only on Leslie Street and at St. Robert CHS.
• On John Street, south of the rail line, 2 Milliken runs to the Finch GO Bus Terminal.

Viva and the subway. There is no Viva stop inside the community; the nearest Viva Purple stops are on Highway 7, north of the 407. No TTC route enters the community. The Yonge North Subway Extension's Bridge station is planned near Langstaff GO, and Metrolinx gives no opening year. Under One Fare, transfers between the TTC and YRT within two hours are free with PRESTO or a bank card.

Driving. The 407 has an exit at Leslie. The 404 has no exit along Thornlea; the nearest to the south is Steeles, and there is no 404 interchange at John Street.

OpenStreetMap shows no shops of any kind inside Thornlea: no supermarket, mall or convenience store. Errands mean leaving the community, and usually crossing the 407, the 404 or the rail line:

• Highway 7, north of the 407: the Times Square and Shoppes of the Parkway malls near Highway 7 and Leslie, and Loblaws, Canadian Tire and a Walmart Supercentre around Highway 7 and Bayview.
• John Street and Bayview, south of the rail line: Thornhill Square Shopping Centre with a Food Basics, and a Longo's on Bayview.
• Steeles at the 404, to the south-east: the Shops on Steeles and 404, with another Food Basics, at one end of YRT route 3.
• East of the 404 and north of the 407: a Costco (1 Yorktech Dr).

These supermarkets and malls are roughly 0.9 to 1.8 km from the community boundary in a straight line, and further on foot. For buyers it is a straight trade between quiet streets and convenience.

Inside the community (by the addresses in the City of Markham parks list):

• Huntington Park (116 Huntington Park Dr): a playground, a soccer field, a ball diamond and an off-leash dog area.
• Summerdale Park (128 Summerdale Dr): a playground.
• Franklin Carmichael Park (277 Green Lane): a playground and a soccer field.
• St. Robert's Soccer Dome (8101 Leslie St, on the St. Robert CHS campus): a YCDSB–City of Markham partnership in which a third of the field is covered by an air-supported dome from October to March; open for rentals and programmes.
• Trails: the Lake to Lake Route multi-use path runs along Leslie Street, and the city describes the 4.2 km Markham section from Highway 7 to John Street as complete; Huntington Trail follows the creek on the west side.

The hydro corridor. An east–west transmission corridor crosses the north of the community; OpenStreetMap shows two 500 kV lines and a 230 kV line running from the 404 side to west of Huntington Park. On a viewing, judge for yourself what it does to views and feel.

Close by, but outside the community: R.J. Clatworthy Arena (2400 John St, south of the rail line); Thornhill Community Centre & Library (7755 Bayview Ave, with two ice pads, a therapy pool, a fitness centre and a library branch); Thornlea Pool & Gymnasium (8079 Bayview Ave, a 25-metre pool); and German Mills Settlers Park (80 German Mills Rd).

Thornlea falls in York Regional Police #2 District, which serves Richmond Hill and the Thornhill area of Markham and Vaughan (nearly 285,000 people) from 171 Major Mackenzie Dr W in Richmond Hill. The basis for that is YRP's open data: the records that fall inside this community all carry district 2.

There are no official crime statistics by TRREB community, and this page does not compile its own by category or per head, nor does it call the area safe or unsafe. For actual figures, use the Crime map and statistics section of YRP's website, which links to the Community Safety Data Portal, crime statistics and an interactive map you can search around an address.

The official plan (Markham Official Plan 2014, July 2024 office consolidation).

• Thornlea's residential area falls inside the plan's Thornhill district, whose northern limit is the edge of the Parkway Belt West (§9.18.1, running roughly from Yonge Street to the 404 and from the Langstaff Gateway and the Parkway Belt West down to Steeles). The district is far larger than Thornlea and its policies apply across all of it; none of them is specific to Thornlea, and Thornlea has no secondary plan of its own.
• On the plan's land-use map (Map 3), most of Thornlea is Residential Low Rise, which the plan describes as "established residential neighbourhoods with lower-scale buildings … which will experience minimal physical change in the future". Permitted forms include detached and semi-detached houses, townhouses (not back-to-back) and small multiplexes of three to six units fronting a public street, up to three storeys; what can actually be built on a lot is set by the zoning by-law. The German Mills Creek valley is Greenway.
• The strip along the 407 is transportation and utilities land under the provincial Parkway Belt West Plan (1978). Under §8.11 of the plan, the provincial plan governs it, and the designations drawn underneath are only potential ones that would apply if the Province released the land, not a current permission to build.

Things that are not in Thornlea and are easy to mix up:

• None of the protected major transit station areas listed for Markham in York Region's 2022 Official Plan (approved with modifications by the Province on November 4, 2022; this page uses the Appendix 2 map from the version sent for approval) is in Thornlea; the nearest, around the Leslie–Highway 7 station, stops north of the 407.
• Section 9.18.12 of the plan says Markham will consult the Region and the Province on the potential for a GO station in the vicinity of John Street and Green Lane. That is beside the Richmond Hill line near Bayview, outside this community to the south-west, and it is a possibility under study, not a decision.
• Nearby applications: 95 Green Lane (a proposal for 18 townhouses, with a statutory public meeting scheduled for February 25, 2026) is west of the creek in Aileen-Willowbrook, and the application at the south-west corner of Leslie and Highway 7 is north of the 407 in Commerce Valley.

Applications inside the community. The city's published planning-application notices and biweekly circulation summaries (roughly December 2023 to October 2026, with some gaps) showed no official plan amendment, rezoning or subdivision application inside Thornlea as of 2026-10-23. Minor variances and severances before the Committee of Adjustment are not in those summaries, so this does not mean there is no development at all.

Adding a unit. According to markham.ca, since the province's Bill 23 every urban residential lot may have up to three residential units; two-unit houses must be registered with the city and pass fire and building safety inspections. Whether a given lot qualifies depends on zoning and a building permit.

Before making an offer on a home in Thornlea, work through these:

• Check the community first. Look at the TRREB community label on the listing. The stretch of John Street south of the rail line is German Mills, and west of the creek is Aileen-Willowbrook; "Thornhill" or "Thornlea" in a listing does not put a house in this community.
• Look up schools by address. Enter the exact address in the YRDSB and YCDSB school locators rather than going by the community or a school's name. The secondary school called Thornlea is on Bayview, and whether it serves a given house depends on the address.
• Age of the house. Most homes here were built in 1981–90 and are now 35 to 45 years old. Focus the inspection on the roof, windows, heating and cooling, wiring, plumbing and basement waterproofing, and ask what has been replaced and when.
• Where the lot sits. Lots backing onto the 404, the 407, the hydro corridor or the rail line may feel different from lots on the creek or on inner streets; visit on a weekday and at a weekend to see and hear for yourself.
• Lots backing onto the valley. Before planning an addition or major alterations, ask both the city and the Toronto and Region Conservation Authority (TRCA) whether the lot falls in a regulated area and needs a TRCA permit.
• Basements and suites. If the house has a rented suite, check that it is registered with the city and has passed its fire inspection.

When selling a home in Thornlea, settle these points before pricing and listing:

• Few comparable sales. Thornlea records only a handful of sales a quarter, so there may be no recent sale of the same model on the same street. When pricing, be explicit about each comparable: which community, the year built, the lot size and the extent of renovation.
• Be specific. Name the schools an address lookup returns rather than quoting rankings; give the distance to the YRT stops on Leslie, Huntington Park and the Lake to Lake trail; and list what has been updated.
• Stand out. Almost every house here is detached and most date from the same decade, so buyers compare them directly. The scope of renovation, the lot (especially one backing onto the valley or a park) and the maintenance record are what set a house apart.
• Do not overstate. Quote sale-to-list ratios and days on market from TRREB's published figures, without claims such as "bidding war" or "fastest in the city".

• Only about 3.5% of households rented in the 2021 Census, and live rental listings are scarce (five in a snapshot taken 2026-10-23), so the rental market is thin and rents are hard to gauge.
• The houses are large detached homes 35 to 45 years old; holding costs should include renovation and upkeep.
• According to markham.ca, an urban residential lot may have up to three units and two-unit houses must be registered; whether adding a suite is possible or worthwhile depends on the lot and the zoning, which this page does not assess.
• This page makes no price forecast and no judgement on cash flow, and is not investment advice.

Thornlea is a clearly bounded, uniform residential area in west Markham, enclosed by the 407, the 404, a CN freight line and the German Mills Creek valley. Almost every home is a detached house, about eight in ten homes were built in 1981–90, and more than nine in ten have four or more bedrooms; residents skew older and very few rent; there are no shops, a hydro corridor crosses the north side, and the parks and valley trail are its strengths. By address, public elementary splits at Leslie into Bayview Glen then German Mills on one side and Bayview Fairways on the other; public secondary is Thornlea SS on Bayview, and the Catholic St. Robert CHS is inside the community. Transit means YRT routes 3 and 90, and GO trains mean Langstaff or Old Cummer, at weekday peaks only. In planning terms it is a low-rise area expected to see "minimal physical change", and the city's application notices and summaries checked for this page (with gaps, and excluding the Committee of Adjustment) showed no planning application inside it as of 2026-10-23. When choosing a Thornlea realtor, the three questions in FAQ 5 below are a quick check on the comparables and school lookups they bring.

One thing to remember about the name: Thornlea Secondary School and Thornlea Pool are on Bayview Avenue, not in the Thornlea community.