Shared walls bring shared costs and shared decisions. A semi-attached or attached property often means a shared roofline, a shared party wall or a shared driveway, and any of those can require a registered agreement through Information Services Corporation covering maintenance and repair responsibility, paperwork a fully detached home never needs.
The gap narrows in specific pockets of the market. First-time buyers priced out of detached homes support attached and semi-attached product strongly in denser, walkable areas, so the discount detached homes usually command over attached ones can shrink or even flip depending on lot size and location rather than holding as a fixed rule citywide.
Joel Dyck prices each category against its own comparable set rather than adjusting one blended detached number. Get your hand-reviewed valuation from Joel Dyck.