Secondary suite
A secondary suite is a self-contained apartment, cottage, or small residential unit that is located on a property that has a separate main, single-family home, duplex, or other residential unit. In some cases, the ADU or in-law is attached to the principal dwelling or is an entirely separate unit, located above a garage, across a carport, or in the backyard on the same property. Reasons for wanting to add a secondary suite to a property may be to receive additional income, provide social and personal support to a family member, or obtain greater security.
Description
Background
Naming conventions vary by time-period and location but secondary suites can also be referred to as an accessory dwelling unit, mother-in-law suite, granny flat, coach house, laneway house, Ohana dwelling unit, granny annex, granny suite, in-law suite, and accessory apartment. The prevalence of secondary suites is also dependent on time and location with varying rates depending on the country, state, or city. Furthermore, regulations on secondary suites can vary widely in different jurisdictions with some allowing them with limited regulation while others ban them entirely through zoning, limit who may live in the units, or regulate if units can be rented.Spatial relationship to main residence
A secondary suite is considered "secondary" or "accessory" to the primary residence on the parcel. It normally has its own entrance, kitchen, bathroom and living area. There are three main types of accessory units: interior, interior with modification, and detached. Examples include:- A suite above a rear detached garage,
- A suite above the main floor of a single-detached dwelling,
- A suite below the main floor of a single-detached dwelling.
- A suite attached to a single-detached dwelling at grade
- A suite detached from the principal dwelling.
- A granny flat, granny annex, mother-in-law cottage and the like are generic familial names for an ADU.
Benefits and drawbacks
Benefits
- Higher density residential areas have many advantages. They require less resources for transport, heating and cooling, infrastructure and maintenance. They allow for closer-knit communities by facilitating interaction between neighbors, especially children and teenagers.
- Creating affordable housing options as secondary suites are typically small, easy to construct, and require no land acquisition.
- Enabling seniors to "age-in-place" by creating small and affordable units where seniors can downsize in their own neighborhood. Some of the recent popularity of secondary suites in the United States can be attributed to the activities of the American Association of Retired Persons and other organizations that support seniors.
- Supporting diverse and multi-generational households as seniors, young-adults, or other relatives can live on the same property as their families while maintaining independence and privacy. For seniors, this arrangement can improve social life, allow to easily provide care, and possibly live in more walkable neighborhoods when they can no longer drive.
- Facilitating homeownership by providing a reliable extra income that can support mortgage payments and home maintenance.
- Creating sustainable and energy-efficient housing as smaller or attached units require fewer resources.
- ADUs can be integrated into the scale and character of single-family neighborhoods while also promoting workforce housing in these neighborhoods.
- Municipal budgets may benefit from new taxable housing that does not require new infrastructure or significant utility upgrades.
Drawbacks
By country
Australia
In Australia, the term 'granny flat' is often used for a secondary dwelling on a property. The land is not subdivided with construction requiring approval from the council or relevant authority. The approval processes vary between States and Territories, and between councils. This is different from a dual occupancy, where two primary dwellings are developed on one allotment of land, being either attached, semi-detached or detached. In 2018, New South Wales led the construction of new granny flats while Victoria had the fewest number of new granny flats constructed. In 2019, the federal government launched a study concerning prefabricated buildings and smaller homes citing affordable housing, extra space for family members, and support for the construction industry as reasons for the study. The government set aside $2 million for the initial study and then plans to set up an innovation lab to help manufacturers design prefabricated buildings.New Zealand
Similar to Australia, a secondary dwelling on a property is also known as a 'granny flat', but more commonly as a 'sleepout'. A sleepout, or 'cabin',:- Is separate from the main house
- Can be used as an extra accommodation, a hobby room, home office or storage
- Does not contain cooking, sanitary facilities or drinking water supply.
- Not exceed 30m2 in floor area
- Be one storey with a height not exceeding 3.5 metres above the floor level
- Have a floor level not exceeding 1 metre off the supporting ground - including mezzanine floors
- Hot contain any plumbing or facilities for the storage of drinking water
- Only be used for sleeping accommodation if the sleepout is used in connection with a dwelling and the sleepout does not contain cooking facilities
- Have a smoke alarm installed if used for sleeping accommodation
- Be sited at least 1 metre from any residential building or boundary, if it measures more than 10 square metres in floor area.
In September 2025, a select committee report called for minor amendments to the government's legislation allowing small homes like granny flats to be built without a consent. The Amendment Bill would allow for standalone dwellings of up to 70 square metres to be built without a consent, so long as certain conditions are met.
The proposed changes, championed by Housing Minister Chris Bishop, were backed unanimously by all parties and the bill is expected to pass by the end of the year.
Canada
Secondary suites have existed in Canada since the 19th century where they took the form of coach houses, servant houses, stables converted to permanent apartments, and small apartments for young people within large houses. Secondary suites became increasingly popular during the economic crisis of 1929 and the housing shortage following WWII. During this period the Canadian government actively supported the creation of secondary suites. However, suburbanization and zoning changes in the 1950s and 60s led to a decrease in secondary suites in Canada. More recently, secondary suites are increasing in popularity and many municipalities are reexamining their regulations to support secondary suites.CMHC (government program)
The Canada Mortgage and Housing Corporation provides a financial assistance program to help Canadians create affordable housing for low-income seniors and adults with a disability within a secondary suite. The program is called the . The maximum fully forgivable loan depends on the location of the property:- Southern areas of Canada: $24,000/unit
- Northern areas of Canada: $28,000/unit
- Far northern areas: $36,000/unit
British Columbia
After adopting legislation in 2009 to support secondary suites, Vancouver, British Columbia has become a leading city of their construction in North America. In the city, approximately a third of single-family houses have legally permitted secondary suites, many of which are laneway houses. The Housing Policy Branch of British Columbia's Ministry of Community, Aboriginal and Women's Services published a guide for local governments to implement secondary suite programs called 'Secondary Suites: A Guide For Local Governments'. The current issue is dated September 2005. The intent of the guide is to "help local governments develop and implement secondary suite programs". It also highlights good secondary suite practices as well as providing practical information to "elected officials, planners, community groups, homeowners, developers, and others interested in secondary suites".Europe
In German speaking countries an interior secondary suite is known as an Einliegerwohnung.In the United Kingdom, "granny flats" are increasing in popularity with one in twenty UK households having such a space. 7% of householders say they have plans to develop this type of space in the future. 27% of those surveyed were making plans for older relatives, 25% were planning for grown-up children, 24% were planning to rent as holiday lets, and 16% were planning to take in lodgers.
In Norway, particularly in the bigger cities, it is quite common to build separate adjoined smaller flats that the owner of the main flat will rent out.
In Sweden, a friggebod is a small house or room which can be built without any planning permission on a land lot with a single-family or a duplex house.