If you’re an architect or built environment professional working on a heritage permit — or even a routine building plan submission — you’ll need to know whether the building you’re working on is older than 60 years.
Why does it matter? Because under the National Heritage Act, any building older than 60 years (or any site on which such a building stands) is protected. That means you need to declare the building’s age in your plans, and getting it wrong has real consequences.
The Obvious Starting Point: Approved Plans
Approved municipal plans are your best source. They’ll tell you when a building was constructed. If you can get them, go to the municipality and request the approved plans on record — that’s your most reliable evidence.
But what if there are no approved plans? That’s where it gets trickier, and where many practitioners get stuck.
The Fallback: The Survey Diagram and General Plan Number
If approved plans aren’t available, look at the survey diagram for the property. The survey diagram records when the land was first surveyed, and crucially, it contains a General Plan number — which tells you when that township or subdivision was established.
For example, a General Plan dated 1983 tells you the land was subdivided in 1983. That gives you a definitive earliest possible date for any buildings on it.
This is a document you can attach to your heritage permit application or building plan submission as supporting evidence of age.
An Important Nuance
The General Plan date tells you when the land was subdivided — not necessarily when the building was constructed. A General Plan from 1984, for instance, doesn’t mean the building was built that year. Construction may have followed a decade later.
That’s why the survey diagram works best as a floor — it establishes the earliest the building could have been built. Pair it with approved plans wherever possible to narrow it down further.
In Summary
| Source | What it tells you |
|---|---|
| Approved municipal plans | Actual construction date — most reliable |
| Survey diagram / General Plan number | Date the land was subdivided — useful fallback |
When approved plans aren’t on record, the survey diagram is a legitimate and useful document to support your application. Know where to find it, and keep it in your toolkit.
noh ARCHITECTS 