Good summary. A few practical things from the GTA heritage side that decide whether a project actually gets through Toronto Heritage Preservation Services without a six-month detour.
Timeline planning is what most homeowners underestimate. A Part V HCD permit in Toronto is realistically 8-14 weeks if your scope is straightforward and your drawings match the district guidelines exactly. Add window or door replacements that are not strict like-for-like and you are usually 4-6 months minimum, sometimes longer if it gets referred to Toronto Preservation Board. Plan accordingly - start the heritage application 60-90 days before you want the building permit submitted, and assume two rounds of revisions.
On materials, the part that catches people: synthetic slate, vinyl windows, and modern composite siding are not approved in most HCDs even when they are visually close to the original. For Cabbagetown, Riverdale fringe, Roncesvalles HCD, the Annex, and the Beaches HCD, you will be specifying real wood windows, real cedar trim, and standing seam metal or natural slate roofs. The 30-50% material premium over modern equivalents needs to be in the budget from day one - not absorbed mid-project.
This dovetails with the broader hidden-cost picture for older Toronto homes that we walked through here for anyone planning a pre-1960 reno: Pre-1960 GTA homes: why 2026 renos need a 20-25% buffer. Heritage adds another layer on top of that buffer. If your contractor has not budgeted for heritage permit revisions and material upcharges, the real number will surprise you.