Toronto has more heritage-designated properties than any other Canadian city — over 9,000 individual properties and 42 heritage conservation districts. If your home is among them, replacing your windows isn't as straightforward as calling a supplier and booking an installation date.
We've completed heritage fenestration projects in several Toronto neighbourhoods. Here's what the process actually involves.
Is Your Property Heritage-Designated?
There are two relevant designations under the Ontario Heritage Act: individual property designation (Part IV) and district designation (Part V). Both impose restrictions on alterations to the exterior — including windows — that are visible from a public street.
You can check whether your property is designated through the City of Toronto's Heritage Register, available through the City's online planning portal. If your property is in a neighbourhood built largely before 1940 — Rosedale, Annex, Cabbagetown, South Riverdale, and many others — it's worth checking even if you're not certain.
What the City Requires
For designated properties, replacement windows visible from the street require a Heritage Permit from the City of Toronto. The City's Heritage Planning staff review applications against the heritage attributes of the property — which typically include the original window size, profile, divided light pattern, and material appearance.
The key principle is that replacements should be "sympathetic" to the original — meaning similar in appearance, proportion, and character. This doesn't necessarily mean identical, but it does mean that a contemporary aluminum casement window is not automatically an acceptable replacement for an original 1910 double-hung wood window.
What "Sympathetic" Replacement Actually Means in Practice
In our experience working through this process, the City's heritage staff are generally reasonable — they want the building to look appropriate from the street, not to trap homeowners with rotting original windows indefinitely.
For most heritage replacement projects, an acceptable outcome involves:
- Maintaining the original window size and opening configuration
- Replicating the divided light pattern (the number and arrangement of glass panes) using simulated divided lites if necessary
- Using a profile with similar visible width to the original
- Selecting a colour appropriate to the property's period
Modern materials — high-quality UPVC or aluminum — are generally acceptable to the City provided the appearance criteria above are met. You are not required to use wood.
The Manufacturing Challenge
The difficulty with heritage replacement isn't the City approval process — it's finding a manufacturer who can produce profiles that replicate historical proportions in modern materials. Standard catalogue profiles don't replicate the appearance of 1910 wood windows. Custom profiles can — but require a manufacturer with the capability and willingness to fabricate to non-standard specifications.
This is work we've done. We can manufacture profiles that replicate historical appearances while incorporating modern double-glazing, low-e coating, and thermally broken frames. The result is a window that satisfies the City's heritage requirements and performs to current energy standards.
Timeline note: Heritage permit applications in Toronto typically take 6 to 10 weeks to process. Plan accordingly — this is not a project you can initiate and complete in the same month.
The Result Is Worth It
We've completed heritage replacement projects where the homeowner went from poorly performing, difficult-to-operate 100-year-old wood windows to modern, airtight, thermally performing replacements — that look appropriate from the street, satisfied the City's requirements, and will last another 40 years without maintenance.
It takes more time and more planning than a standard replacement. But the performance improvement in a draughty century home is dramatic.
Have a heritage property that needs new windows?
We've navigated this process before. Book a consultation and we'll walk you through it.
