A Two-Stage Data-Driven Framework for Accessory Dwelling Unit Feasibility Screening and Preliminary Cost Assessment in Urban Neighbourhoods

The global housing crisis reflects a persistent imbalance between supply and demand, intensified by restrictive land-use regulations, housing financialization, and zoning practices that constrain incremental densification. Accessory Dwelling Units (ADUs) provide a sustainable pathway for infill housing by reusing existing serviced land and infrastructure, supporting United Nations Sustainable Development Goal 11, Sustainable Cities and Communities, while offering homeowners an affordable route to additional rental income. However, implementation remains constrained by complex regulations and a lack of integrated feasibility tools. This study develops a two-stage data-driven framework: Stage 1 integrates regulatory, geometric, and image-based constraints, including a YOLOv8n-cls roof-type classifier, for automated parcel-level screening; Stage 2 evaluates construction costs and financial performance for detached ADUs built above an existing garage using light wood frame (LWF) and cross-laminated timber (CLT) construction. In Edmonton, Canada, Stage 1 screens 296,749 parcels and identifies 8691 flat-roof detached garages, of which 7925 are located in permitted zones and considered in Stage 2, comprising 1619 single and 6306 double garages. Under optimistic assumptions, LWF achieves payback periods of 4.8–5.0 years compared with 6.1–6.7 years for CLT. Under conservative assumptions, these increase to 15.7–16.3 and 19.0–20.8 years, respectively, as undiscounted values extrapolate beyond the 10-year analysis horizon, with construction cost and rental income being the principal factors affecting payback. Full-cost homeowner financing remains positive under optimistic conditions but turns slightly negative for CLT Configuration B under conservative conditions. The framework unifies parcel-level screening with preliminary cost and financial assessment, providing a basis for identifying affordable infill housing opportunities and supporting sustainable urban densification.