Courtier Immobilier Montréal Yanick E Sarrazin

Converting a duplex or triplex (plex) into a cottage (single-family home): a project that is gaining in popularity

Cottage coloré du Mile-End au Plateau Mont-Royal

Conversion of a plex into a single-family home - Neighbourhoods in Montreal

A unique real estate project

One of the properties that Montrealers are particularly interested in is single-family homes. The only problem is that in certain neighbourhoods like Le Plateau Mont-Royal or Rosemont-La-Petite-Patrie, single-family homes are becoming scarce and are the subject of fierce competition! So quickly listed on the market, they are quickly sold and often outbid. Since it is very rare to find vacant lots to build, converting a duplex or triplex into a cottage is a project that is gaining popularity with families who want to create a unique product that reflects their needs.

However, in the last year, several boroughs have adopted new regulations in order to compensate for the lack of rental housing in the metropolis. Regulations are very different from one neighborhood to another, and our real estate brokers have decided to enlighten you 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 borough of Plateau-Mont-Royal has announced that the number of units in a two-unit building as of March 16, 1995 can be reduced despite the minimum number of units prescribed with the exception of duplexes with mezzanines. 

However, even though the borough chose to allow conversions, they made the decision to do so by imposing limits on the area. From now on, if you want to convert your duplex into a single-family residence or expand your building, the living area must not exceed 200 square metres, 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 limited the conversion of triplex into a family residence, but allows the conversion of duplexes with a processing permit.

The houses on the same level, which are omnipresent in the neighbourhood, have opportunities for expansion. For more information, we recommend reading our article on enlargements on shoebox.

Duplex à Villeray à Montréal


In the borough of Villeray, for buildings up to six apartments, it is possible to merge two of them if the area does not exceed 200 m2. The area of a basement is excluded from this calculation. The conversion of a duplex in Villeray could therefore be accepted with a processing permit.  Based on the previous instruction, it is therefore no longer possible for triplex owners to convert their home into a single-family home. This prohibition remains the same for the conversion of rooming houses.

Maison unifamiliale à Ville-Marie à Montréal


The borough of Ville-Marie indicated that the conversion of a building with a dwelling, in order to reduce or increase the number of dwellings, requires the obtaining of a permit and the approval of the work.

Le Sud-Ouest

The Sud-Ouest borough indicated that the conversion of a duplex or triplex requires a processing permit. This would imply that it is possible to carry out your conversion project as long as it does not affect the minimum number of dwellings per building in the area. So you have to apply for a licence and hope to be approved.


The borough of Mercier-Hochelaga-Maisonneuve states that the conversion of duplex and triplex into single-family homes is always possible with the obtaining of a conversion permit.


The borough of Outremont, for its part, indicates that the conversion of a duplex or a triplex requires a transformation permit. It is therefore possible to carry out your conversion project once you have applied for a permit and have been approved by the borough’s permit and inspection division.


The borough of Côtes-des-Neiges-Notre-Dames-de Grâce allows the reduction of triplex to duplex, as well as duplex to single-family homes. These conversions are permissible as of right, regardless of the area limits relating to the number of dwellings.

*Please note that regulations may change, so please contact the boroughs for more information.

Facade d'un cottage du Plateau Mont-Royal

Suggestions from our real estate brokers

In all cases, our team strongly suggests that you make sure to obtain numerous building permits: demolition permits, permits for transformation or construction, permits for excavation or other, according to your needs and contact management to have the work approved by the borough’s Urban Design and Business Services Branch.

Our real estate brokers in Montreal answer your questions

Have additional questions?

For any questions, you can always refer to the website of the city of Montreal or contact directly the boroughs, since it is up to the borough to determine whether the loss of housing or of dwellings resulting from this conversion will not contribute to the minimum amount of housing required in the neighbourhood. However, your real estate broker remains the best person to accompany you in all your projects and guide you in finding the ideal income property to carry out your conversion. 

Questions? Contact one of our real estate brokers