ADU
An ADU, or Accessory Dwelling Unit, is also known as a secondary suite, a laneway house, an in-law flat, or a basement apartment, among others. This secondary living area includes private kitchen and bathroom facilities, and may be within, attached to, or completely detached from the main dwelling.
ADU Suitability
This was calculated by considering a number of factors, including:
- Size of lot
- Size of main dwelling
- Size of ADU Buildable Area
- Existence of a secondary structure (i.e. garage)
- Zoning district
- Building Type
- Flood plain status of lot
- Availability of required parking
Some of these factors can immediately disclude a lot from building an ADU, including:
- Size of lot
- Size of main dwelling (if it is less than 40 square meters)
- Zoning of Lot (lot is zoned other than RD1, RD2, or RD3)
- Building Type (lot does not contain a single family dwelling, semi-detached, or townhome dwelling)
Some of these factors may exclude a lot from building an ADU, but further information and investigation would be required. These factors include:
- Size of ADU Buildable Area (If it is less than 40 square meters, an internal or attached ADU may still be possible)
- Existence of a secondary structure (If the structure can be modified or removed, a detached ADU may then be possible)
- Zoning of Lot (lot is zoned RD3)
"All requirements are met, but located in RD3"
Properties zoned as RD3 are high-density housing areas, meaning they are eligible for medium- to large-scale multi-unit dwellings, and are therefore potentially ineligible for an ADU.
"All requirements are met, except for parking"
Our estimates indicate that there is not space on the lot to accommodate the required parking spot. If this is the only missing requirement, a lot may still be eligible for an ADU if a parking space can be made available elsewhere (for example, in the existing driveway), or special permission is given to not have one.
Amenity Proximity Score
Measures how close a Dissemination Area is to another Dissemination Area that contains a particular amenity. This proximity is then expressed as a score between 0 and 1, with 0 being farthest and one being closest to that amenity. The score is determined based on how well this area's proximity to that amenity compares to the rest of Canada.
For more information, visit the Proximity Measures Data Viewer on statcan.gc.ca.
Buildable Area
This space is calculated by configuring the appropriate setback from property lines and the main dwelling. It does not account for secondary structures (such as detached garages, pools, and sheds), and there may be some overlap between the ADU buildable area and these structures.
Dissemination Area
The smallest standard geographic measure in Canada, Dissemination Areas (DAs) are drawn to have a population between 400 and 700 people.
Flood Plain
An area of land that is prone to flooding. Municipal bylaws restrict ADU construction in these areas.
High Density Housing
Residential area containing a medium to large multi-unit dwelling (double duplex, lodging house, multiple dwelling).
"Located in RD3 and parking requirements are not met"
This lot is zoned for high-density housing, and our estimates show that it may not have the space to allow for the necessary tenant parking. However, depending on the type of building on the lot, and parking availability not visible in this tool, an ADU may still be possible.
Low Density Housing
Residential area containing predominantly single unit dwellings, semi-detached dwellings, and/or townhomes.
Main Building is less than 40 sq. m
ADUs are intended to be smaller than the main dwelling, and the minimum size for an ADU is 40 square meters. With a main dwelling sized at 40 square meters or less, these two requirements cannot be met simultaneously.
Medium Density Housing
Residential area containing predominantly small to medium multi-unit dwellings, typically less than 4 units (duplex, triplex, double duplex,).
Minimum and Maximum ADU Size
Our tool assumes a 40 square meter, one storey ADU. The minimum and maximum ADU size combines both lot coverage restrictions and size restrictions in relation to the main dwelling.
For lots larger than 400 square meters: the minimum ADU size is 40 square meters, and the maximum ADU size is 100 square meters, but not more than 10% of the total lot area, and must be smaller than the main dwelling.
For lots less than 400 square meters: ADUs can be no smaller and no larger than 40 square meters, in order to adhere to lot coverage and minimum ADU size requirements. This means that an ADU may end up as larger than 10% of the lot coverage, but only when necessary to ensure it meets the minimum 40 square meters minimum.
e.g. If the lot is 390 square meters, 10% of the lot area would be 39 square meters. This would violate the 40 square meters minimum size of an ADU and therefore, an ADU on this property can only be 40 square meters.
"No single-unit, townhome, or semi-detached"
The building type on this lot is not eligible for any additional dwellings.
Planning District
In order to develop more detailed planning policies, municipalities may divide their geography into smaller parcels called "Planning Districts." These districts are often of unequal size, and are chosen based on physical, social, and economic characteristics of the region.
"Secondary structure exists, but can have ADU"
Despite the secondary structure present on this lot, there is still enough buildable area to accommodate an ADU within the lot coverage restrictions.
"Secondary structure must be removed or modified"
This lot would be able to accommodate an ADU if the secondary structure (garage, shed, etc.) did not take up as much of the buildable area.
Setback
This is the minimum distance from the property line that a building is required to be built.
I.e. The side and rear property lines have a 1.2m setback for a detached ADU. This means that the ADU must have at least a 1.2 metres space between the ADU walls and property boundaries/main dwelling.
