Secondary suites and accessory dwelling units (ADUs) have been moving from a niche tactic to a mainstream housing tool for homeowners and municipalities. As part of this change, financing and provincial/municipal policy are aligning to encourage legal, safe suites; however, regulatory details still vary by jurisdiction. Local due diligence remains essential.

Key Federal Policy Change That Shifts Economics

A key national change in 2025 was the federal move to make mortgage-insurance-backed refinancing available to help homeowners add secondary suites. As of January 15, 2025, the change allows insured refinancing that can include the anticipated value of new secondary units and permits refinancing up to 90% of a home’s value (with program caps and qualifying rules). The program and related mortgage-insurance rule adjustments explicitly require that added unit(s) not be used as short-term rentals and carry standard occupancy and equity requirements. This change can improve the cash flow case for owners who previously struggled to access low-cost capital to create legal suites.

Provincial and Municipal Frameworks Remain a Gating Factor

While the federal financing change lowers a major economic barrier, provincial and municipal rules determine if a unit can be built, what the requirements are, and how quickly it can be legalized. Provinces have been clarifying that ADUs and secondary suites are permitted uses in many zones, but the path varies.

British Columbia’s provincial guidance asks owners to check local land-use rules and follow the BC Building Code for construction and safety, and it provides plain-language resources to help homeowners and builders understand title restrictions and bylaw interactions. Municipal pages in Metro Vancouver, including Vancouver’s dedicated secondary suite web pages and district zoning schedules, show that cities typically require permits, plan review and adherence to zoning district schedules; some Vancouver district schedules explicitly limit the number or type of suites allowed on a lot.

Municipalities in Alberta and the Prairies have also been active. Edmonton publishes a practical secondary suite guide and a municipal page that explains permitting and inspection requirements; Calgary likewise maintains clear permit guidance for new secondary suites, and in many Calgary neighbourhoods, backyard suites and basement suites are now both possible on a single lot where zoning allows. These municipal resources confirm local allowance, maximum number of units, occupancy rules and utility/solid-waste arrangements.

Calgary demonstrates how incentives, rules, and regulations keep changing. After introducing its secondary suite incentive program in 2024, it announced a new change in June 2025; incentivized secondary suites will not be approved for a Short-Term Rental business licence for two years.

Ontario’s planning changes of recent years have pushed municipalities to allow additional residential units more broadly; the province has also signalled regulatory amendments intended to reduce the need for rezoning or minor variances for many ADU projects. However, municipal implementation, permitted performance standards, and tree/landscape or parking expectations remain local matters and can vary considerably across councils. Agents must therefore confirm both the provincial policy direction and the municipality’s current zoning and any pending changes.

As an example, Vaughan permits one secondary suite in detached, semi-detached, or townhouse dwellings, with rules on minimum lot frontage, suite size (at least 35 m² and no more than about 45% of the main dwelling), and parking requirements. The city most recently updated its Secondary Suites Information Guide in November 2022 to reflect the province’s Additional Residential Unit policies. Hamilton also broadened permissions, allowing one internal secondary unit and, in many cases, one detached unit per lot. Key zoning by-law amendments adopted in 2021 and updated further in June 2022 clarified where suites are permitted across most residential zones while outlining building code and parking standards.

Building Code and Safety Standards

Across Canada, the National Building Code (and its provincial/territorial adaptations) establishes minimum technical requirements for fire separation, egress, ventilation and alarms. Recent code updates (for example, Ontario’s 2024 Building Code coming into force for permits in 2025) change technical thresholds and transitional rules that affect permit timing and costs. Practical implications for clients include minimum ceiling heights, required escape windows in bedrooms, mandatory smoke and CO alarms, and sometimes independent mechanical systems or clear separation between units. Those technical items drive design costs and the timeline for legalization, but also protect resale value and insurability.

Key Trends

A key trend is that municipalities are increasingly focused on legalizing existing suites and ensuring their safety rather than criminalizing them; many cities now offer legalization processes or inspections rather than automatic fines, although penalties apply where registration or permits are required and not obtained.

While increased financing makes more projects viable, lender underwriting and program rules will include restrictions, such as prohibiting STR use, and insurers and mortgage insurers will apply their own criteria to cash flow calculations and value estimates. In short, demand and feasibility are improving, but profitability also depends on getting the permit and code work right.

Practical Steps and Client Messaging

For clients considering a secondary suite in 2025, the first step is confirming what’s actually allowed on the property and what standards apply. Municipal zoning maps, district schedules, and title searches can show whether suites are permitted, while building departments confirm the safety and code requirements before any work begins.

Real estate professionals can’t provide technical or legal advice, but they can add value by spotting properties that are good candidates, noting features that might reduce upgrade costs, and pointing out challenges like parking or servicing limits. For sellers, this means knowing whether an existing suite is fully legal and insurable before promoting it as income-producing and considering this when pricing. For buyers and investors, it means checking if the property can realistically support a legal suite, and connecting with experienced planners, builders, and lenders and sharing other resources. By guiding clients toward realistic expectations and reliable resources, agents help ensure secondary suites are both achievable and financially worthwhile.