The Ultimate Guide to Legal Basement Apartments in Ontario

In today’s real estate market, where rental prices remain high and affordable housing is scarce, many homeowners in Toronto and Montreal are considering the option of building a legal basement apartment. This additional dwelling unit can serve as a source of extra income, help pay off mortgages faster, or provide more space for extended family members. However, before embarking on this venture, it is crucial to understand the legalities involved in creating a basement apartment in Ontario and Quebec.

In this comprehensive guide, we will break down the core components of a legal basement apartment, explore the requirements set by the Ontario Building Code and Quebec regulations, discuss the costs associated with the renovation process, and weigh the pros and cons of renting out a basement apartment.

What Makes a Basement Apartment Legal in Ontario?

To qualify as a legal basement apartment in Ontario, the unit must meet the requirements outlined in the Ontario Building Code. It is important to note that the term “basement apartment” is not used in the code itself. Instead, it refers to these units as “second units” to encompass all additional dwelling spaces within a home, regardless of their location.

The key criteria for a legal basement apartment in Ontario include:

  1. Meeting the Ontario Building Code Requirements: A legal basement apartment must adhere to the Ontario Building Code standards for second units. This includes meeting minimum size requirements, ceiling height specifications, window sizes, plumbing and electrical standards, and fire safety regulations.

  2. Complying with Local Municipal Zoning By-laws: Local municipalities have the authority to allow or prohibit basement apartments within their zoning codes. It is essential to check the specific regulations of your municipality to ensure that basement apartments are permitted in your area.

  3. Being in an Existing House Older than 5 Years: The Ontario Requirements for Second Units only apply to houses that are older than 5 years. If your house is less than 5 years old, it may be subject to the new Ontario Building Code, and you should consult professionals in the building industry for guidance.

  4. Meeting Specific Standards for Second Units: There are four key standards that second units in Ontario must meet: size requirements, ceiling height requirements, window requirements, and fire safety requirements. These standards ensure that the basement apartment provides a safe and habitable living space.

Size Requirements

The minimum size of a legal basement apartment in Ontario varies depending on the number of bedrooms it contains. For a bachelor unit (with combined eating, living, and sleeping areas), the minimum size is 145 square feet. It is important to note that these measurements are based on finished surfaces and do not include closets.

Ceiling Height Requirements

A legal basement apartment in Ontario must have a minimum ceiling height of 1.95 meters (approximately 6.4 feet). In cases where the ceiling has a slope, such as in attic second units, at least 50% of the floor area must have a ceiling height of 2.03 meters (approximately 6.7 feet). This requirement ensures that the living space is comfortable and meets the minimum standards for habitability.

Window Requirements

Windows play a crucial role in providing natural light and proper ventilation in a basement apartment. The size of the windows required depends on the floor area they serve. Generally, the living and dining room windows must be at least 5% of the floor area, while bedroom windows must be at least 2.5% of the floor area. It is important to note that windows are not required in laundry rooms, kitchens, or bathrooms.

Plumbing Requirements

To be considered a legal basement apartment, the unit must have hot and cold water supply, a sink, a kitchen sink, and access to laundry facilities. Additionally, the basement apartment should have separate water shut-off valves from the main unit and may require a backwater preventer valve based on the specific situation. If the house has a septic system, it must be capable of supporting the additional load from the basement apartment.

Heating and Cooling

Legal basement apartments in Ontario can share the furnace and ducts with the main unit. However, they must be equipped with special smoke detectors in the ducts that comply with UL268A standards. These detectors are designed to shut off the furnace in the event of an emergency. Ventilation is also required in the bathroom and kitchen of the second unit, which can be achieved through windows or exhaust fans.

Electrical Requirements

A legal basement apartment must have a light switch in every room, as well as switches at the top and bottom of the stairs, if applicable. The electrical work in the second unit must be inspected and approved by a licensed Electric Safety Authority (ESA) electrician. The electrician will provide a certificate or place a special sticker on the main breaker panel for the unit, indicating compliance with electrical safety standards.

Fire Safety Requirements

Fire safety is of utmost importance in a legal basement apartment. There must be a minimum of 30 minutes of fire separation between the basement apartment and the main unit, either in the ceiling or walls, depending on the orientation of the second unit. If the entire house has interconnected smoke alarms, the required fire separation can be reduced to 15 minutes. Smoke alarms are mandatory on every level of the home or unit, in the common area outside sleeping areas, in each bedroom, and in any shared or common areas such as the laundry room. In cases where the furnace room is separate for the secondary unit, a smoke alarm is also required in that space.


Legal basement apartments may have a common exit with the main dwelling unit if the smoke alarms are interconnected. However, if the primary entrance to the basement apartment is through the main unit, a second means of escape must be provided. This is a common violation in basement apartments and can be addressed by creating an acceptable window exit that allows for safe egress in case of emergencies.

What Makes a Basement Apartment Legal in Quebec?

In Quebec, the regulations surrounding basement apartments vary based on the location of the unit. The provincial regulations primarily focus on the availability and specifications of an egress window, which serves as a second means of escape. An egress window must be large enough for both a child and an adult to climb through and must be operable without any anti-intrusion bars.

In addition to these provincial standards, municipalities in Quebec often have their own specific rules and regulations for basement apartments. For instance, Montreal has particular requirements regarding the configuration, ventilation, lighting, appliances, exits, and other aspects of second dwellings. It is crucial to consult the local regulations and obtain the necessary permits and approvals before proceeding with the construction or renovation of a basement apartment in Quebec.

Codes and By-laws for Renting Your Basement

Before renting out a legal basement apartment, it is essential to ensure that your space meets all the necessary codes and by-laws. In both Ontario and Quebec, there are multiple codes and regulations that must be followed to ensure the safety and habitability of the basement apartment.


In Ontario, a legal basement apartment must comply with the Ontario Building Code, the Ontario Fire Code, and the specific by-laws of the municipality where the property is located.

The Ontario Building Code sets out the minimum standards for construction, including size requirements, ceiling height specifications, window sizes, plumbing and electrical standards, and fire safety regulations. It is advisable to hire a property inspector or general contractor to assess your basement and determine if any updates or renovations are necessary to meet the Ontario Building Code requirements.

The Ontario Fire Code establishes the fire safety standards for buildings, including second units. It is essential to have your basement apartment inspected by the fire department to ensure compliance with these regulations. However, passing the fire department inspection does not automatically make your basement apartment legal. You must also meet the requirements of the Ontario Building Code and any additional by-laws specific to your municipality.

Each municipality in Ontario may have its own by-laws and processes related to basement apartments. For example, Toronto, Mississauga, Brampton, Milton, Burlington, and Hamilton have specific regulations that may be more restrictive than the Ontario Building Code. It is crucial to familiarize yourself with the by-laws of your municipality and obtain any necessary permits or approvals before renting out your basement apartment.


In Quebec, the regulations for renting out a legal basement apartment depend on the location of the unit. All buildings in the province, including legal basements, must meet the standards set by the Régie du bâtiment du Québec (RBQ), which is responsible for enforcing the Quebec Construction Code.

The RBQ’s standards cover various aspects of building construction, including structural requirements, fire safety measures, plumbing and electrical systems, and ventilation. It is crucial to ensure that your basement apartment meets these standards before renting it out.

Additionally, each municipality in Quebec may have its own specific rules and regulations regarding basement apartments. For example, Montreal has particular requirements for second dwellings, such as ventilation, lighting, appliances, and exits. It is essential to consult the local regulations and obtain the necessary permits and approvals before renting out your basement apartment in Quebec.

The Costs of Creating a Legal Basement Apartment

Creating a legal basement apartment can be a significant investment, and the costs involved will vary depending on several factors, including the condition and layout of the basement, the desired amenities, and the location of the property. While it is challenging to provide an exact cost estimate, we can outline some of the common expenses associated with renovating a basement into a legal living space.

Renovation Costs

The cost of renovating a basement to create a legal apartment can range from tens of thousands to over $100,000, depending on the scope of work and the finishes chosen. A typical benchmark for a turnkey basement renovation without a bathroom is around $45,000 in Montreal and $70,000 in Toronto for an area of approximately 900 square feet. However, it is important to note that these estimates reflect the cost of finishing a basement, not specifically creating a legal second dwelling.

To transform an unfinished basement into a legal basement apartment, additional costs will be incurred. These costs may include installing a full bathroom, creating an independent entrance, upgrading plumbing and electrical systems to meet code requirements, and ensuring proper fire safety measures. According to industry professionals, a complete transition from an unfinished basement to a legal basement apartment typically starts at $85,000, excluding taxes, based on a model of 900 square feet.

It is crucial to obtain quotes from reputable contractors or renovation specialists to determine the specific costs for your project. They can assess the existing conditions, discuss your desired layout and finishes, and provide a detailed estimate that takes into account all the necessary elements for a legal basement apartment.

Additional Costs and Considerations

In addition to the renovation costs, there are other expenses and considerations to keep in mind when creating a legal basement apartment:

  • Inspection and Certification: You may need to pay for inspections by professionals, such as structural engineers, electricians, and plumbers, to ensure that the renovation work meets all the necessary codes and regulations. Certification fees may also apply to obtain the required documentation for a legal basement apartment.

  • Permits and Approvals: Depending on your municipality, you may need to obtain various permits and approvals before starting the renovation work. These permits typically come with associated fees that should be factored into your budget.

  • Property Taxes: Renovating your basement to create a legal apartment could potentially increase the assessed value of your property, leading to higher property taxes. It is advisable to consult with your local tax authority to understand the potential impact on your property taxes.

  • Ongoing Maintenance and Upkeep: As a landlord, you will be responsible for the ongoing maintenance and upkeep of the basement apartment. This includes repairs, regular inspections, and addressing any issues that may arise during the tenancy.

  • Insurance: It is important to review your homeowner’s insurance policy to ensure that it covers a basement apartment. You may need to adjust your coverage or purchase additional insurance specifically for the rental unit.

It is crucial to have a realistic budget in place and consider all the potential costs associated with creating a legal basement apartment. Consulting with professionals and obtaining multiple quotes will help you make informed financial decisions and ensure that you are adequately prepared for the expenses involved.

Pros and Cons of Renting Out a Legal Basement Apartment

Before deciding to rent out a legal basement apartment, it is important to weigh the advantages and disadvantages. Here are some of the pros and cons to consider:


  1. Additional Income: Renting out a legal basement apartment can provide a steady source of additional income, helping to offset mortgage costs or generate extra cash flow.

  2. Increased Property Value: Adding a legal basement apartment can increase the value of your property. It appeals to potential buyers who may be looking for additional rental income or space for extended family members.

  3. Flexible Use: A legal basement apartment can serve various purposes, such as providing housing for family members, accommodating guests, or acting as a home office or studio.

  4. Mitigating the Housing Crisis: By offering a legal basement apartment, you contribute to addressing the shortage of affordable housing in your community, providing a safe and regulated living space for tenants.

  5. Tax Benefits: Renting out a basement apartment may provide certain tax benefits, such as deducting eligible expenses related to the rental unit from your income tax.


  1. Reduced Privacy: Renting out a basement apartment means sharing your home with tenants, which may result in a loss of privacy. Noise and disturbances from tenants can also be a potential issue.

  2. Costs and Responsibilities: Creating a legal basement apartment involves significant upfront costs for renovations, inspections, and permits. As a landlord, you are responsible for ongoing maintenance, repairs, and addressing tenant issues.

  3. Legal and Regulatory Compliance: Ensuring that your basement apartment meets all the necessary codes, by-laws, and regulations can be complex and time-consuming. Failure to comply with these requirements can have legal and financial consequences.

  4. Tenant Management: Being a landlord requires time, effort, and effective tenant management skills. Dealing with tenant inquiries, collecting rent, and addressing tenant concerns can be demanding.

  5. Tax Implications: Renting out a second unit may have tax implications, including rental income tax, which you need to report to the provincial government. Familiarize yourself with the tax regulations and consult with a tax professional to understand your obligations.

It is essential to carefully consider these pros and cons, assess your personal circumstances, and determine if renting out a legal basement apartment aligns with your goals and lifestyle.


Creating a legal basement apartment in Ontario or Quebec can be a viable option for homeowners looking to generate additional income or accommodate extended family members. However, it is crucial to understand the legal requirements, costs, and responsibilities involved before proceeding with the renovation process.

By adhering to the Ontario Building Code requirements and local municipal regulations, homeowners in Ontario can ensure that their basement apartments meet the necessary standards for safety and habitability. In Quebec, it is essential to comply with the provincial regulations and any specific rules set by the municipality.

The costs associated with creating a legal basement apartment can vary depending on factors such as the condition of the basement, desired amenities, and location. It is advisable to obtain quotes from reputable contractors or renovation specialists to accurately estimate the renovation costs.

Renting out a legal basement apartment has its advantages, such as additional income and increased property value. However, it also comes with responsibilities, including ongoing maintenance, tenant management, and compliance with legal and regulatory requirements.

Before embarking on the journey of creating a legal basement apartment, it is crucial to conduct thorough research, consult professionals when needed, and carefully evaluate the potential benefits and challenges. By doing so, homeowners can make informed decisions and create a safe and compliant living space that meets the needs of both tenants and landlords.

If you have any further questions or need assistance with your basement renovation project, feel free tocontact us. We are here to help you navigate the process and provide guidance along the way.

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