What is the difference between an ADU and a Secondary Suite ?
An Additional Dwelling Unit (ADU) is the broad, modern umbrella term that encompasses all types of self-contained residential units on a single property. A Secondary Unit is a specific classification of an ADU that is integrated within the primary house structure
Key Differences in Classification
| Feature | Additional Dwelling Unit (ADU) | Secondary Unit |
|---|---|---|
| Scope | Includes all unit types: detached, attached, or internal. | Typically refers specifically to units inside the main house (e.g., basements). |
| Location | Can be in the backyard (Garden Suite), above a garage, or in a lane. | Almost always within the footprint of the primary residence. |
| Terminology | Preferred by provincial "Gentle Density" mandates and modern planning. | Common in older municipal by-laws and the Ontario Building Code (OBC). |
| Common Examples | Garden Suites, Laneway Houses, Garage Conversions. | Basement Apartments, In-law Suites, Second Suites. |
