Courtier Immobilier Montréal Yanick E Sarrazin

The conversion of a duplex or triplex (plex) into a cottage (single-family house): a project gaining popularity

Converting a plex into a single-family house - Neighborhoods in Montreal

A unique real estate project

One of the real estate assets that particularly catches the eye of Montreal residents is that of single-family houses. The only issue is that in certain neighborhoods like Le Plateau Mont-Royal or Rosemont-La-Petite-Patrie, single-family houses are scarce and subject to fierce competition. Quickly listed on the market, they are swiftly sold, often in bidding wars. Since vacant lots for construction are very rare to find, the conversion of a duplex or triplex into a cottage is a project gaining popularity among families aiming to create a unique product that reflects their needs.

However, over the past year, several boroughs have adopted new regulations to address the shortage of rental housing in the metropolis. The regulations vary significantly from one neighborhood to another, and our real estate brokers have decided to shed light on the subject. Here are the new regulations regarding the conversion of triplex or duplex into single-family homes in each of the boroughs of the city of Montreal.*

Cottage moderne au Plateau Mont-Royal à Montréal

Le Plateau-Mont-Royal

The Plateau-Mont-Royal borough has announced that the number of units in a two-unit building existing as of March 16, 1995, can be reduced despite the prescribed minimum number of units, with the exception of duplexes with a mezzanine.

However, even though the borough has chosen to allow conversions, they have decided to impose limits on the area. From now on, if you wish to convert your duplex into a single-family residence or expand your building, the habitable area must not exceed 200 square meters, or approximately 2,152.78 square feet. This floor area of the dwelling must be calculated by adding the area of each floor, including a mezzanine, but excluding a basement floor.


Duplex à Rosemont-La Petite-Patrie à Montréal

Rosemont-La Petite-Patrie

The borough of Rosemont-La Petite-Patrie has restricted the conversion of triplexes into single-family residences but does allow the conversion of duplexes with the acquisition of a transformation permit.

The ubiquitous bungalow-style houses in the neighborhood have opportunities for expansion. For more information, we recommend reading our article on expansions in shoebox houses.

Duplex à Villeray à Montréal


In the borough of Villeray, for buildings with up to six apartments, it is possible to merge two of them if the total area does not exceed 200 square meters. The area of a basement is excluded from this calculation. Therefore, the conversion of a duplex in Villeray could be accepted with the acquisition of a transformation permit. Following the previous guideline, it is no longer possible for owners of triplexes to convert their units into single-family houses. This prohibition also applies to the conversion of rooming houses.

Maison unifamiliale à Ville-Marie à Montréal


The borough of Ville-Marie indicates that the transformation of a building containing a residence, with the aim of reducing or increasing the number of units, requires obtaining a permit and approval for the work.

Le Sud-Ouest

The borough of Sud-Ouest indicates that the transformation of a duplex or triplex requires a transformation permit. This implies that it is possible to proceed with your conversion project as long as it does not affect the minimum number of units per building in the area. Therefore, you need to apply for a permit and hope for approval.


The borough of Mercier-Hochelaga-Maisonneuve states that the transformation of duplexes and triplexes into single-family homes is always possible with the acquisition of a transformation permit.


The borough of Outremont, on the other hand, states that the transformation of a duplex or triplex requires a transformation permit. Therefore, it is possible to proceed with your conversion project once you have applied for a permit and have been approved by the borough’s permits and inspection division.


The borough of Côte-des-Neiges-Notre-Dame-de-Grâce allows the reduction of triplexes to duplexes, as well as the conversion of duplexes to single-family homes. These conversions are permitted by right, regardless of sector limits related to the number of units.

*Please note that regulations may change. Therefore, we encourage you to inquire with the borough for the most up-to-date information.

Facade d'un cottage du Plateau Mont-Royal

Suggestion de nos courtiers immobiliers

In all cases, our real estate brokers strongly recommends ensuring that you obtain various construction permits, such as demolition permits, transformation or construction permits, excavation permits, or others, as needed. Additionally, it is advised to contact the Urban Planning and Business Services Division of the borough to have the work approved by the municipal authorities.

Additional questions?

For any questions, you can always refer to the City of Montreal’s website or directly contact the boroughs, as it is the responsibility of the borough to determine whether the loss of housing resulting from this conversion will not contribute to falling below the minimum required quantity of housing in the neighborhood. However, your real estate broker remains the best person to assist you with all your projects and guide you in finding the ideal income property for your conversion.

Feel free to contact us; our team has experienced real estate brokers in this type of purchase in various neighborhoods of Montreal, and we will be happy to guide you through all the steps of this complex process.

Phone: 514.799.9841

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