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ADU: accessory dwelling units in Quebec

#Real estate in Quebec

Last update : 2023-11-29 12:47:57

Are you familiar with accessory dwelling units? Better known by the acronym ADU, these small properties, sometimes compared to tiny homes, are becoming increasingly popular in Canada. But they come with their own set of challenges!

In Quebec, in particular, their use remains limited due to restrictive regulations in most cities. Yet many experts agree that their wider use would bring multiple benefits, for citizens and communities alike.

Here's a look at ADUs in the Quebec real estate sector.

What is an accessory dwelling unit?

To better understand the issues surrounding ADUs, let's start by defining what they are.

An accessory dwelling unit (ADU) is a dwelling built on a lot occupied by a main building. It shares its lot with another, larger, existing building.

It's important to note that the term "accessory dwelling unit" and its abbreviation refer to several types of secondary units. In fact, there are more than fifty different names for them: secondary dwelling, accessory dwelling, backyard house, and so on.

Examples of ADU (in fench)


Thus, depending on the characteristics of the main building and the area in which it is built, the ADU can take different forms:

  • Accessory dwelling: a dwelling unit built inside the residence (for example, in a garage or basement).
  • Attached accessory dwelling unit (AADU): an addition to the existing building (side addition or addition of a floor).
  • Detached accessory dwelling Unit (DADU): a small detached house that is not attached to the building.

The 4 main principles of ADU design

According to Arpent, a nonprofit urban planning firm that provides land use planning services, there are four main principles of ADU design:

1. Small size

The ADU is a small unit. It must be proportionally smaller than the main dwelling (generally less than half the living area of the main building). Depending on the environment in which it is built, it can occupy between 15% and 50% of the lot's open space.

2. Harmony

The integration of the ADU is harmonious. The new unit must be in harmony with the residence and the neighbourhood in which it is located. It can imitate the original architectural style or integrate it more originally, depending on the vision of the architect and the regulations in force.

3. Privacy

The ADU must provide privacy. It must be reasonably placed on the lot. The location of doors and windows must not interfere with the privacy of the occupants or nearby neighbours.

4. Environment

ADU construction takes environmental considerations into account. In several cases, its design promotes sustainable development. Several regulations also encourage the use of green roofs, green walls, ecological heating systems, etc.

Small room decor

ADU: a new concept in housing?

Contrary to popular belief, the ADU concept is not new. It goes back many, many years.

Indeed, this type of property was particularly popular during the 19th century and the first half of the 20th century. In Canada, ADUs developed largely as a result of the economic crisis of 1929 and the housing shortage following World War II.

However, the phenomenon almost completely disappeared a few years later, between 1950 and 1960. Economic prosperity and suburban development reduced the need for second homes. In this context, many municipalities banned ADUs in their zoning and building codes.

Since the 1990s, however, there has been a resurgence of interest in ADUs among many Canadian households. Nevertheless, many cities have not yet changed their bylaws to allow ADUs.

The advantages of ADUs

If ADUs have enjoyed a resurgence in popularity in recent years, it's because they offer several benefits. This is true for both citizens and municipalities.

Benefits for citizens

  • By enabling the creation of an intergenerational home, ADUs can encourage mutual support and strengthen ties between generations.
  • In the context of an aging population, they are a solution for keeping seniors at home, especially when built to universal accessibility standards.
  • They also promote access to affordable housing for low-income households.
  • The development of an ADU provides a supplemental source of income, reducing the financial burden on homeowners.

Economic growth

Benefits for communities

  • ADU construction reduces urban sprawl and densifies existing neighbourhoods. The land is better utilized.
  • The new units generate additional property tax revenue for the municipality.

The introduction of accessory dwelling units to the area therefore kills two birds with one stone, as both the city and its citizens benefit.

Limitations of accessory dwelling units

Inadequate regulations are undoubtedly one of the major obstacles to the construction of ADUs in Quebec. But it's not the only one. Several technical challenges and economic concerns also stand in the way of the implementation of these units:

  • Uncertainty about the value of the land;
  • Concerns about the rentability of the home;
  • Fear of increased density;
  • Fear of potential changes to the neighbourhood.

In fact, many homeowners are opposed to new housing being built near their homes. While they recognize the merits of the concept, few are willing to implement it in their own backyard at the risk of having to change their lifestyle.

Regulations in Quebec

For citizens interested in adding an extra unit to their home, the project is not an easy one. It's not for nothing that the use of ADUs remains limited in Quebec: municipal bylaws are sometimes a real obstacle to their implementation.

Several Quebec cities do not allow the construction of ADUs. Others do, but only under strict conditions. For example, it may be required that the new home be occupied only by family members, making it impossible to rent to strangers.

Given this situation, many experts argue that municipalities need to develop more flexible rules. Not only to encourage the construction of ADUs but also to encourage households to declare them. After all, many ADUs are still built "clandestinely" and informally.

Neighbourhood seen from above

Municipalities that accept ADUs in Quebec

It should be noted, however, that several Quebec cities have already begun the process of facilitating the installation of ADUs on their territory.

This is the case of Sainte-Catherine, on the south shore of Montreal. With 98% of its territory built up, the town saw accessory dwelling units as a solution to its problems, particularly in terms of homeownership for its residents.

In addition to Sainte-Catherine, the Municipality of Mont-Saint-Hilaire has also modified its bylaws to accommodate these citizen choices, as many homeowners in its area have adopted AHUs despite the ban.

The city of Longueuil is currently considering the densification of its sectors. It is therefore expected that the framework for ADUs will change in the next few years.

And what about Montreal? The regulations on accessory units vary from borough to borough. Ville-Marie and Plateau-Mont-Royal are among the boroughs that accept them, especially if they are located in basements.

Taking inspiration from Ontario: a good idea?

To promote the presence of accessory suites throughout the province, many experts believe that Quebec would benefit from taking a leaf out of its neighbour Ontario's book.

Since 2011, the Ontario government has required municipalities to amend their bylaws to allow for the use of secondary suites. In 2016, Ottawa even became the first city in the province to adopt a clear and precise framework for ADU development.

Elsewhere in the country, the cities of Vancouver, Calgary, Edmonton and Hamilton also have regulations that Quebec could learn from.

Interested in accessory dwelling units? You can use this opportunity to start a discussion with your municipality.

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