Is your Toronto detached home really a semi-detached? Be careful of this zoning workaround when buying

When buying a so-called “detached” home in Toronto built in the 1970s or 1980s, you might want to double-check what you’re actually getting. Homes that look fully standalone above ground may in fact be built on shared foundations or garages. These are often marketed as detached, but under the rules they’re technically a semi-detached structure—a detail that can affect resale value and zoning compliance. Real estate and legal experts are warning buyers to tread carefully.

In many neighborhoods of Toronto, particularly those developed in that era, builders used a zoning loophole to save on costs. They would build two houses that appear separate above grade, but share a common wall or slab underground. These are known as “linked houses.” Above ground they look like detached homes, but because of a shared foundation or garage wall, they do not meet the legal definition of fully detached.

The distinction may seem minor, but it matters. If a home is legally semi-detached or linked, it may fall under different zoning rules that restrict future renovations, extensions, or adding a secondary unit. It can also affect financing and insurance, since lenders and insurers often distinguish between true detached and attached properties.

For buyers, the best protection is proper due diligence. Ask your agent for zoning documents and floor plans, and consult a lawyer who can look at surveyor records or municipal zoning history. Look specifically for shared walls or foundations—even if you can’t see them, they may exist underground. An experienced home inspector or engineer may spot clues like narrow utility alleys or clues in the property layout.

Most people assume that if a house has space between it and the neighbor, it must be detached. But in linked-house setups, the gap may be less than it seems—a narrow unusable alley separating two very close homes. That alley is not a shared wall, but the homes still share structural elements below ground. It’s this hidden connection that makes a house legally attached even if it doesn’t look like it.

Toronto isn’t alone in facing this issue—many cities built linked housing in similar ways. But it’s especially common in Toronto’s older suburbs, where zoning rules for semi-detached lots were stretched by developers seeking higher profits. To avoid surprises, buyers should verify the zoning classification and condition of title before closing. What looks detached may not have the same value or flexibility as a truly standalone home.