A beloved architectural gem dating back to the turn of the 20th century could become the base for a new condo building if a new development proposal is approved.

A fresh application from developer Prowinko seeks to place a modern addition above an old apartment block at 41-45 Spadina Road, with the two combining to form a new 15-storey structure.

Known as Spadina Gardens, the block of heritage apartments at Spadina and Lowther was constructed circa 1905. The four-storey apartment block, in the Edwardian Classical style, is one of the city's oldest such buildings, designated as a heritage building by the City of Toronto.

Prowinko's application proposes to float a ten-storey architects—Alliance-designed addition with 70 condominium units above the existing building, retaining the current heritage structure and its 24 rental units in its entirety.

And, let me stress emphasis on the word float.

While plopping condos atop a heritage building is nothing innovative, this project's plan to coexist with its base building really sets it apart from the standard Toronto value-maximizing exercise.

Aside from a central elevator core and a southern support column spanning the tower, this proposal seems to hover weightlessly above the retained heritage component.

Planning documents specify that the existing heritage building would be retained in-situ, suggesting that residents of the current complex would not be displaced during construction. New levels would be set back from the street in an effort to minimize the addition's impact on the street below.

According to a document filed with City planners this month, "The proposed massing strategy maintains the prominence of the existing heritage building from the public realm, while appropriately distinguishing and locating new construction above it with a sensitive and innovative massing, material, and design strategy."

Beyond the impressive structural engineering at play here, the plan's bid to retain the existing rental units and leave the heritage building almost entirely undisturbed is worth acknowledgement in a Toronto where demo-victions are the norm.

Despite leaving the apartments untouched, the incongruity of a tower plopped onto a heritage apartment block and the proposed height compared to surrounding structures are sure to ruffle some feathers.