As one of the city's largest neighbourhoods slowly moves from the drawing board to reality, planners and politicians are struggling to decide which of the old buildings can be cleared to make way for the new.

Don Mills Crossing will transform 50 hectares of land around the intersection of Don Mills Road and Eglinton Avenue East from largely commercial properties to a mix of uses, including homes for 10,000 families, as well as parks, businesses, affordable housing and retail space.

"It's a massive change," said Deputy Mayor Denzil Minnan-Wong, whose Don Valley East ward includes the new neighbourhood. "A lot of it has to do with new transit lines being brought in here."

The heart of the new neighbourhood will be its transit hub: the Eglinton Crosstown LRT will run through the centre of the new development, and the northern terminus of the TTC's proposed new subway relief line — called the Ontario Line — will be near the Don Mills-Eglinton intersection.

"Over the next 10 years there'll be some big changes ... We're prospering and because we're becoming a transit hub with the Don Mills Crossing and the Ontario Line, there's going to be more development," Minnan-Wong said.

"We have to get it right."

The area along Eglinton Avenue East that is to be redeveloped, as it looks now. (Google Street View)

Artist's rendition of how the city hopes the area will look about 10 years from now. (City of Toronto)

Before any shovels are in the ground though, the city must decide what to do with the current structures in the area, many of which qualify for protection as heritage sites, city staff and politicians say.

At last week's meeting of North York community council, staff presented a list of eight properties that they say should be on the city's heritage register. Another seven, they said, warrant consideration and further discussion with the buildings' owners.

Coun. James Pasternak, who chairs the North York community council, says the difference between a heritage building and a derelict one can be 'in the eye of the beholder.' (Mike Smee/CBC)

According to correspondence received by the city, some of those owners are balking at the heritage designation because of the limits it can impose on the value of their properties.

And Minnan-Wong acknowledges some of the sites on the "preserve" list might not be obvious choices.

The towering Foresters building, for instance, which was built in 1967.

This office building at 1200 Eglinton Ave. E., had been slated for preservation as a heritage site until it was deemed to be structurally unsound and removed from the list by councillors last week. (Google Street View)

"You want to protect the history of Don Mills, there's no question about that," he said.

"Although, I wouldn't be surprised if someone would wonder why the Foresters building, or some of these other properties that wouldn't seem to be special in any obvious type of way would be put on the list so nothing could ever happen to these buildings."

Another structure, the Computer Sciences Canada building at 1200 Eglinton Ave. W. was on the list, but staff removed it when it became apparent it was structurally unsound and would need to be torn down.

In all, 15 buildings have made the city's list for possible preservation.

Map showing the future site of the community to be known as Don Mills Crossing, shaded in orange. (City of Toronto)

But at the Jan. 8 meeting of North York community council, politicians agreed to pare the list down to just eight, and continue to study the remaining seven. That decision will have to be approved — or altered — by city council at its meeting later this month.

Once on the city's heritage register, developers face limitations on what they can do with the property.

"When it's fully listed as a heritage site, it's very hard to do anything with it," said Coun. James Pasternak, who chairs the North York community council. "You can't change the facade, you can do some minor internal renovations; it can't be demolished."

Even so, Pasternak said he wants to ensure nothing's torn down simply to make way for the new.

Coun. Minnan-Wong, with the former Celestica headquarters, built in the 1950s, in the background. That structure has already been scheduled for inclusion on the city's heritage register and will be at least partially protected when the new Don Mills Crossing community is built. (Mike Smee/CBC)

"What we have to be careful of is not to demolish our history," he said. "Once these buildings are torn down, that's it, they're gone forever.

"It's all in the eye of the beholder. Sometimes various design and architectural characteristics are very appealing to some people, and in others they don't resonate."

The plan to retain some of the current structures as heritage sites goes to city council later this month.

Both Minnan-Wong and Pasternak said it will be years before the project is complete.

Some of the buildings on the Celestica site, which covers most of the development's northeast quadrant, have already been designated for preservation.

The former Celestica headquarters, built in the 1950s, for instance, which sits at 844 Don Mills Rd., just north of Eglinton, will be saved. On the Celestica site's western edge, at 1150 Eglinton Ave. E., the brown, blocky buildings on the north side of Eglinton just east of the railroad tracks, will also be partially retained in the new development.

The Bell Canada building on Wynnford Drive, erected in 1969, is being nominated for heritage protection by city staff developing the new Don Mills Crossing neighborhood. (City of Toronto)

On the south side of Eglinton west of Don Mills, on city-owned land, 800 affordable rental units, plus 1,400 market-priced units and some commercial space will be built, according to city planner Christian Ventresca, who quarterbacked the redevelopment plan through its early stages, between 2013 and 2016.

He said the development will include towers of up to 47 storeys, as well as townhouses and office buildings.

"You're building a new neighbourhood, a new community." Ventresca said.

Until the redevelopment plan began to take shape, he said the area of the city was "a place between places; it's a blank on everybody's mental map.

"It really is an exciting time in terms of connecting neighbourhoods in the Don Mills and Eglinton area," he said.

"We have ... varying housing types, from townhouse to tower. But also as importantly, new public infrastructure as it relates to parks, daycare, community facilities, all connected by a new street network that tries to make both sides of pretty heavily trafficked arterial corridors in Don Mills and Eglinton work together."