Additional Dwelling Units on the Property: Types, Terminology, and Recommendations
In Ontario, homeowners are increasingly considering adding Additional Dwelling Units (ADU, SDU, Garden Suite) to their properties to expand living space, rent it out, or provide housing for family members. Below is detailed information on each type of Additional Dwelling Unit, their differences, terminology, and practical recommendations for those planning to build a larger unit, such as up to 1,500 sq. ft.
Key Terms
- Secondary Dwelling Unit (SDU) – A secondary dwelling unit is an additional living space integrated into the main house, often in the basement or attic. SDU requires minimal changes to the existing structure and is an internal part of the main building.
- Accessory Dwelling Unit (ADU) – An accessory dwelling unit is a broad term covering both built-in and stand-alone structures, such as a Garden Suite. An ADU may include additions or separate buildings on the property and usually has independent utility connections.
- Garden Suite – A garden suite is a separate building in the backyard of the main house, typically not exceeding 60 sq. m (646 sq. ft). Garden Suites are often used to house elderly relatives or for rental purposes.
Features and Requirements for Each Type of Dwelling Unit
Secondary Dwelling Unit (SDU)
- Location: Integrated into the main building, such as in the basement or attic.
- Maximum Size: Typically up to 807 sq. ft or not more than 75% of the main building’s area.
- Purpose: Used as an extension of the main living space; rental is usually permitted.
- Permitting Process: Simple permit process, as SDU usually follows zoning for the main building.
- Timeline and Costs: Fast process (4-6 weeks), lower cost compared to ADU.
Accessory Dwelling Unit (ADU)
- Location: Can be integrated, attached, or a stand-alone structure, such as a garage or Garden Suite.
- Maximum Size: Typically up to 807 sq. ft, though larger sizes are allowed on a case-by-case basis.
- Purpose: Independent living space, can be used for rental or personal use.
- Permitting Process: More complex, requiring additional documentation, including zoning and utility connections.
- Timeline and Costs: Lengthy process (6-10 weeks), higher cost compared to SDU.
Garden Suite
- Location: Separate building in the backyard of the main house.
- Maximum Size: Typically 60 sq. m (646 sq. ft) or up to 40% of the backyard area.
- Purpose: Independent dwelling, often used for relatives or rental.
- Permitting Process: Simplified process compared to ADU, standard zoning for small backyard structures.
- Timeline and Costs: Fast process (4-8 weeks), moderate cost, often lower than ADU.
Why is Garden Suite a Quick and Simple Option?
The Garden Suite generally requires fewer approvals compared to an ADU, as it is not part of the main house and has size limitations. Its construction often does not require modifications to the existing structure and requires standard zoning for small, stand-alone buildings. A Garden Suite can be built in 4-8 weeks, making it an ideal choice for homeowners looking to quickly expand their living space.
