Converting a Duplex Into a Single-Family Home in Montreal: The Borough and the Tenant Decide First

The idea is appealing: buy a duplex in a central neighbourhood, merge the two units and get a large house for less than a single-family home in the same area. In Montreal, that plan depends on two decisions that are not yours: the borough's, which may or may not allow the merger, and the sitting tenant's, whom the law protects strongly. Here is what to check before making an offer.

First obstacle: borough rules

In Montreal, much of urban planning is handled by boroughs, and several have tightened their rules on merging units. La Presse reported in July 2024 that boroughs such as Le Plateau-Mont-Royal, Verdun, Mercier–Hochelaga-Maisonneuve, Villeray–Saint-Michel–Parc-Extension and Rivière-des-Prairies–Pointe-aux-Trembles were adopting or studying stricter rules, which differ from one borough to the next:

• in Rivière-des-Prairies–Pointe-aux-Trembles, a by-law banning both merging and subdividing units, except to return a building to its original layout, such as separating a duplex that had been merged in the past;
• in Le Plateau-Mont-Royal, a proposal to send every merger request to the borough council, with a $2,785 review fee;
• in Verdun, a freeze on merger permits as soon as the by-law study began.

These rules may have changed since. The only reliable answer comes from the borough, for the specific address, before you make an offer.

Second obstacle: the sitting tenant

If the second unit is rented, merging it means getting it back. Quebec's Administrative Housing Tribunal notes that the act assented to on June 6, 2024 bars, for three years, evictions to subdivide a dwelling, enlarge it substantially or change its use, subject to exceptions set out in the act.

Outside the moratorium, eviction is still tightly framed: written notice at least six months before the end of a lease of more than six months, the tenant's right to refuse, the landlord's duty to prove to the Tribunal a genuine intent that is not a pretext, and compensation of one month's rent per year of uninterrupted lease, between three and twenty-four months, plus reasonable moving costs.

In practice, buying a rented duplex to merge it quickly is not realistic during the moratorium.

What to check before the offer

• Zoning and borough rules for the address: required or permitted number of units, whether merging is allowed, procedure and fees.
• The building's history: a duplex that was originally a house may fall under a return-to-original-layout exception, where one exists.
• Occupancy: vacant, rented, or occupied by a relative of the seller. Leases and their end dates are read before the offer.
• Technical feasibility: stairs, entrances, separate services. A contractor or architect can price the conversion.
• Financing: the lender finances what exists, a duplex, not the planned house.

A condition to write into the promise

If the conversion is the reason for buying, it belongs in the promise to purchase as a condition: obtaining written confirmation or a permit from the borough within a set time. Without it, you are buying a duplex, with its tenants and its rules. Our article on plex zoning in Montreal explains how to read the zoning for an address.

Keeping the duplex may be the best option

A duplex you can't merge is not a bad deal for all that. Living in one unit and renting the other helps carry the mortgage, and rental income counts in the lender's analysis under its rules. Before giving up on a house project, compare the net monthly cost of this setup with that of a single-family home in the same area.