Case study · decided file
The Committee Approves a Garden Suite in Willowdale
17 Theresa Ave · two-storey garden suite in the rear yard · approved 2026
The subject has 23.5 m of measured rear yard behind the house. Of 643 measured lots nearby, 603, or 93.8%, have at least 7.5 m of rear yard.
This is a retrospective demonstration study. The Committee of Adjustment already decided this application, and the file is a public record. Daniel Du was not retained on the matter. We prepared this analysis after the decision, as a work sample. It states no planning opinion.
The package includes the report (PDF), print-ready map and chart exhibits (PNG), the data tables with a data dictionary (CSV), a methods note (TXT), the interactive map (HTML).
The interactive map is one HTML file. Open it from disk in any browser. Each threshold has a slider and an exact-value box, and the counts and headline update as you move them. You can change the colours, outlines and fill, switch to a colour gradient, or add a satellite, topographic or building footprint background. Click any mapped feature to see its record. The map works offline. The satellite and topographic backgrounds need an internet connection. The package also includes this same file.
How it is measured
We measure every low-rise residential lot within 500 m from parcel geometry in EPSG:2952. Lot depth is lot area divided by frontage, the planning convention. Frontage is the extent of the street-facing edge, measured along the street.
For each lot with a hosted building footprint we take the largest footprint as the main house, as the height studies do. We build a lot-aligned frame from the street-facing edge, the same construction the setback and building envelope studies use. The rear yard depth is the gap, measured along the depth axis of that frame, between the back of the main footprint and the lot line furthest from the street.
The subject is a corner lot. It fronts two streets. We take Theresa Ave, the addressed street, as the front, so the rear lot line is the line opposite Theresa Ave. We apply the same rule to the other 162 corner lots in the cohort and we keep them in the statistics. The median rear yard is 15.4 m for mid-block lots and 18.2 m for corner lots.
We exclude 9 lots where the largest footprint is a garage or where the footprint sits mostly outside the parcel. Those cases give a gap that does not belong to a house. 9 residential lots have no hosted footprint and appear neutral on the map.
The 7.5 m screen is an illustrative working threshold for a two-storey garden suite plus separation from the main house. It is not a by-law test. The garden suite regulations set their own setbacks, height limits and separation distances, and only a full zoning review applies them to a lot. The 10 m band marks lots that clear the screen with room to spare.
Committee precedent comes from Committee of Adjustment records within 500 m, filed from 2015 onward. We search the description field for 'garden suite', 'laneway suite' and 'ancillary', case-insensitive. The wider count adds 'accessory building', 'accessory structure' and 'accessory dwelling'. The open record is thin for this building type, so the counts are small and we report them as they are.