Québec garden houses
The provincial as-of-right rule does not cover a detached garden house. Local zoning does. French terms on this page are the ones municipalities use.
Last verified 13 October 2026
Plein droit provincial
Until 20 August 2029, a municipality cannot prohibit an accessory unit inside a detached single-family house (conditions apply). This does not cover detached garden houses. Those depend on local zoning, and a municipality can opt out of parts of the framework.
Permits
Check zoning with the municipality or borough, then a building permit. A surveyor's site plan and a PIIA architectural review are sometimes required. The work must meet the Code de construction du Québec, and the contractor must hold an RBQ licence.
Ville de Québec
A maison de jardin has been allowed since June 2024. One additional unit per lot, at most 75% of the main house footprint and 80 m², on a real foundation (piles or slab; elephant-foot blocks do not count), with a walkway to the street. Allowed with detached homes and, more recently, semis, duplexes, and triplexes.
Montréal
Rules vary by borough. Some, including Rosemont–La Petite-Patrie, have adapted their by-laws, and PIIA review may apply. Feasibility is checked lot by lot.
Gatineau
A permanent detached accessory building needs a permit and must follow accessory-building zoning (setbacks, area, height). Gatineau's 2025 construction by-law R-534-2025 requires sound insulation for accessory units and sets minimum areas: 18.5 m² for one habitable room and 30 m² for two rooms, plus 10 m² per extra room.
Open item: confirm whether Gatineau zoning currently allows a detached dwelling unit, and in which zones. Do not treat this page as that confirmation.