The Hypothetical Detached ADU Regulation (HDR) is a set of hypothetical bylaws for detached ADUs. Our team designed the HDR in consultation with ADU advocates from municipal planning services and the planning field to model the potential for detached ADUs in cities without existing regulations in Quebec.
ADUSearch users can use the HDR mapping tool to identify areas where there exists a high potential for detached ADUs, to consider the impact of allowing detached ADUs, and to consider how they would legislate a detached ADU policy that is responsive to their community’s needs.
Our team has designed the HDR to be responsive to local neighbourhood characteristics. The HDR’s detached ADU requirements, therefore, are more permissive in urban areas than in suburban areas. To identify local neighbourhood characteristics, we used 2021 census data to categorize census tracts into three distinct typologies: urban, intermediate, and suburban.
Census tracts were considered Urban if they had all three of the following criteria:
Census tracts were considered Suburban if they had all three of the following criteria:
Census tracts were considered Intermediate if they had a mix of both urban and suburban criteria.
The HDR adapts setbacks, ADU placement, required main dwelling type, and main dwelling setbacks based on the assigned typology of the lot. For lots in Suburban typologies, the HDR applies a lot coverage maximum of 40%, applies main dwelling and lot line setbacks of 2 meters, and limits buildable areas to rear and side yards. The HDR also requires the main dwelling be a single-family home in order to identify the lot as suitable for a detached ADU.
For lots in Intermediate typologies, the HDR applies a lot coverage maximum of 50% and reduces main dwelling and lot line setbacks to 1.5m. It also allows for detached ADUs on lots where the main dwelling unit is a townhouse, a plex, or single-family dwelling.
For lots in Urban typologies, the HDR does not apply lot coverage maximums or lot line setbacks. Like in the Intermediate typology, it allows for detached ADUs on lots where the main dwelling unit is a townhouse, a plex, or single-family dwelling.
Based on these building requirements, the HDR calculates buildable areas for lots that meet the main dwelling type requirement and fall under the HDR lot coverage maximums. Lots also need to fall outside of any environmental protection or natural hazard area where development is typically precluded, such as a floodplain. The minimum size ADU in the HDR is 30 meters squared. Any lot with a calculated buildable area that is equal or more than 30 meters is categorized as suitable for an ADU in the HDR.
For more details and background about our HDR methodology and analysis, visit our Data Exports page to read our methodological report.
