The portrait the borough of Verdun filed with the Office de consultation publique de Montréal in 2017 put the island at 20,461 inhabitants at the 2016 census — against 18,315 in 2011 — over 3.7 km², with 9,635 households, 3,785 of them one-person, and growth concentrated among the 65-to-74 age group (+22%) and people 75 and over (+26%).
The property assessment roll explains all the rest. It records 8,661 residential units spread over 2,273 civic addresses, and 60.1% of those units — 5,202 dwellings — hang on 31 addresses alone, each of 100 units or more; 15 further addresses carry between 50 and 99. At the other end of the range, 2,206 addresses hold a single dwelling, on lots whose median area is 209.5 m²: row housing, not suburban bungalows. Add 562 accessory condominium units — 445 indoor parking spaces, 75 storage spaces, 42 outdoor parking spaces — a signature you will not find in a plex neighbourhood.
Another local trait: not one residential unit here was built before 1961. The oldest dates from 1967, the newest from 2025. The 1980s delivered 30.5% of the stock — 2,602 units now turning forty, the age at which windows, balconies, roofs and underground garages come due — and 52.3% of the stock is later than 2001. The work here is therefore not the heavy restoration of an old building: it is the inside of a condo being redone, and an entire building brought up to standard by its board.
Portrait-diagnostic de la population de L'Île-des-Sœurs, Raymond Chabot Grant Thornton for the borough of Verdun, October 3, 2017 (OCPM file P105, 2011 and 2016 censuses), and the City of Montreal's "Unités d'évaluation foncière" file, extract published August 12, 2026 — recounted and consulted August 17, 2026.