Renovating · Extension · Longueuil
In Longueuil the permit is applied for online at midnight, but the real question is settled beforehand: on your street, is the extension worth what it costs? Here is the 2026 process, the costs, and the comparison with selling and buying again.
In Longueuil, any increase in floor area (storey, annex, attached garage, sunroom) requires a building permit, and the city has digitized the process: the application is filed on the Permis en ligne portal, 24 hours a day, with digital plans and a credit card, one file per type of work; some small permits are issued on the spot, an extension is reviewed by an inspector who replies by email, and the city reports delays lengthened by the volume of applications. The fee follows the municipal fee by-law and is shown on filing. Zoning varies greatly from one sector to another: Vieux-Longueuil and its old houses have PIIA sectors and heritage to respect, Saint-Hubert and Greenfield Park line up 1950s to 1980s bungalows and two-storey houses where adding a storey or a rear annex is common. The cost of the work follows the 2026 industry ranges ($250 to $450 per square foot on a full foundation, $200 to $400 for a storey), $100,000 to $160,000 for 400 square feet. The value created is judged on closed sales in the same sector: in a bungalow neighbourhood, a house extended to 2,000 square feet does not resell at the price of two-storey houses in another sector.
| Item | Rule (longueuil.quebec, Permis en ligne) |
|---|---|
| Requirement | Building permit for any extension (storey, annex, attached garage, sunroom, veranda) |
| Filing | Permis en ligne portal, 24 hours a day, 7 days a week, with digital plans and a credit card; every type of permit and certificate can be applied for online |
| Issue | Some simple permits (pool, balcony, interior renovation, exterior repair) are issued immediately under conditions; an extension is reviewed and approved by email |
| Limit | One application at a time per type of work |
| Fee | Per the city's fee by-law, shown when the application is filed |
| Delay | Not guaranteed; the city reports high volume; the delay runs from the complete file |
| Documents | Certificate of location, site plan, scaled construction drawings, cost estimate, structural details for a storey |
Check before the plans: the sector's zoning grid (setbacks, lot coverage, height, number of storeys), the PIIA sectors (Vieux-Longueuil in particular) and the servitudes; a minor variance adds two to three months.
| Type of extension | Typical 2026 cost (Dessins Drummond estimates, August 2026) | Typical project |
|---|---|---|
| Ground-level extension on a full foundation (basement) | $250 to $450 per square foot | 400 sq ft at the back: $100,000 to $160,000 |
| Ground-level extension on piers or a slab | $200 to $390 per square foot | Cheaper, no basement |
| Second storey added on the existing house | $200 to $400 and more per square foot | 800 sq ft: $160,000 to $320,000 and more, depending on structure and roof |
| Attached garage | $180 to $240 per square foot | 400 sq ft: $72,000 to $96,000 |
| Four-season sunroom | $250 to $325 and more per square foot | 300 sq ft: $75,000 to $97,500 |
These ranges are industry estimates, before taxes, excluding plans ($2,000 to $8,000 depending on the architect or technologist), permits and contingencies (allow 10% to 15%); an extension that touches the roof, plumbing, electrical or load-bearing structure lands at the top of the range. Three detailed quotes from RBQ-licensed contractors, with a schedule and a holdback, remain the only way to get a price.
An extension is rarely recovered in full at resale: in a sector where comparable houses already have the added area, the value created comes close to the cost; in a sector of smaller houses, it caps at what the market pays for the best house on the street, and the excess is lost. The honest comparison: the cost of the extension (plus 6 to 14 months of work and municipal taxes that rise with the assessed value) against the cost of selling and buying bigger (commission, notary, welcome tax, moving: about 8% of the price, $50,000 to $60,000 on a $650,000 to $700,000 house) and the price gap between the two houses. A broker who knows the sector's closed sales can price both options within a week, before you pay for plans.
Yes, for any increase in floor area, including a storey, an attached garage, a sunroom or a veranda; the permit is obtained before the work and an inspector visits the site.
About $100,000 to $160,000 in 2026 for a ground-level extension on a full foundation, taxes, plans and permit extra, according to industry estimates.
Partly: the value created depends on the sector's comparable sales and caps at what the market pays for the best house on the street; compare with selling and buying bigger.
Six to fourteen months from plans to completion, including several weeks for the permit, longer if the project needs a minor variance or an architectural integration approval (PIIA).
Before extending, compare with the other option: the cost of selling, renovating before selling and the 2026 renovation grants.
The Loaa & Manseur team, led by Lotfi Manseur and Loaa Al Daow, is the number 1 team at RE/MAX Platine in 2024 and 2025, 6th RE/MAX team in Quebec, 15th in Canada and in the global top 50 of large residential teams according to the official RE/MAX ranking, computed on actual transactions. Its Google profile counts 221 reviews with a 4.9 rating. Its offices are at 55 avenue de l'Équinoxe in Brossard, one bridge from the island, and every broker's licence can be checked in the OACIQ public register. Three things to verify yourself before calling us, and to demand of any other broker.
Also available in French: version française de ce guide.
Published September 7, 2026 by the Loaa & Manseur team, the number 1 team at RE/MAX Platine in 2024 and 2025, 6th RE/MAX team in Quebec, 15th in Canada and in the global top 50 according to the official RE/MAX ranking. Tell us about your project.
Équipe no 1 de RE/MAX Platine en 2024 et en 2025, 6e au Québec, 15e au Canada et dans le top 50 mondial au classement officiel RE/MAX. Réponse en moins de 24 heures, sept jours sur sept.