Accessory Dwelling Unit Permit Process - Montréal

Housing and Building Standards Quebec 3 Minutes Read · published February 11, 2026 Flag of Quebec

In Montréal, Quebec, adding an accessory dwelling unit (ADU) — often called a secondary suite, basement apartment or accessory unit — requires compliance with municipal zoning and building rules as well as provincial construction standards. This guide explains the typical permit process, inspections, common compliance issues and next steps for homeowners and landlords in Montréal. Always confirm requirements with the city and the Régie du bâtiment du Québec before submitting plans.

What is an accessory dwelling unit (ADU)?

An ADU is a self-contained residential unit located within or accessory to a single-family or multi-unit building. ADUs must meet zoning, safety, habitability and parking rules established by the city and provincial building code.

Before you apply

  • Confirm zoning: check whether your property zoning permits an ADU and any size or occupancy limits.
  • Prepare plans: include floor plans, exits, fire separations, and utilities layouts.
  • Check provincial rules: ensure compliance with the Construction Code and energy and safety requirements enforced by the Régie du bâtiment du Québec (RBQ).
Start with a pre-application discussion with the borough urban planning office to avoid common refusals.

Applying for a permit

Most ADU projects require a building permit and possibly a zoning variance or certificate of authorization. Submit signed plans, a completed permit application, and the owner authorization when applicable. Processing times and required documentation vary by borough and project scope.

  • Application form: complete the city building permit application for construction or renovation.
  • Fees: fees depend on the scope and borough; check the municipal fee schedule.
  • Timelines: typical review may take several weeks; more complex files take longer.

Inspections & compliance

Approved permits include mandatory inspections at prescribed stages (foundation, framing, plumbing, final). Non-compliance found during inspections can result in stop-work orders and requirements to correct work before proceeding.

  • Inspections: scheduled by the permit office; do not conceal work before inspection.
  • Corrective orders: the city may issue orders to remedy unsafe or non-compliant conditions.
  • Report concerns: property complaints and enforcement contacts are handled by municipal by-law enforcement or borough inspection services.
Keep inspection records and permit numbers until final occupancy certification is issued.

Penalties & Enforcement

Enforcement is carried out by borough inspection and the city’s by-law enforcement units, with procedures for orders, fines and court referral. Specific fines, daily penalties, or exact escalation amounts are not specified on the city pages linked in Resources; confirm amounts with the permit office or borough enforcement unit.[1]

  • Monetary fines: amounts and per-day continuing offence rates are not specified on the cited municipal permit pages.
  • Escalation: typical enforcement follows warning, order to comply, fine, and possible court action when unresolved; specific ranges are not specified on the cited page.
  • Non-monetary sanctions: stop-work orders, orders to demolish or alter, and court injunctions may be used.
  • Enforcer & complaints: contact borough by-law enforcement or the city permit office to file complaints or request inspections; see Resources for contact pages.
  • Appeals & review: appeal routes and time limits vary by instrument; if a permit or order is refused or issued, the borough or city permit office provides appeal information—specific statutory appeal time limits are not specified on the cited permit page.

Applications & Forms

The city publishes building permit application forms and guidance; where a separate ADU form exists it will appear on the municipal permits page. If no dedicated ADU form is available, use the standard building permit application and include required drawings and owner declarations.

Do not start construction until you hold an approved permit and all required inspections are scheduled.

Common violations

  • Unpermitted occupancy or unapproved conversion of rooms.
  • Missing required fire separations, egress or smoke detectors.
  • Failure to obtain or display required permits during construction.

FAQ

Do I always need a permit to create an ADU?
Yes. Most ADUs require a building permit and may require zoning approval or a certificate; check with your borough.
Can I rent my ADU short-term (airbnb)?
Short-term rental rules are regulated separately; you must verify municipal licensing and zoning rules before offering short-term stays.
How long does approval usually take?
Typical permit review takes several weeks; complex or variance requests take longer. Check the borough processing times.

How-To

  1. Confirm zoning eligibility and any parking or unit-size restrictions.
  2. Prepare drawings and technical documents to meet the Construction Code and local standards.
  3. Submit the building permit application with plans, owner authorization and required fees.
  4. Schedule and pass required inspections at each construction stage.
  5. Pay any fees, resolve corrective orders and obtain final occupancy certification.
  6. Keep records and contact the borough permit office for amendments, renewals or appeals.

Key Takeaways

  • ADUs need both zoning and building approvals in Montréal.
  • Plan for inspections and documentation to avoid stop-work orders.

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