As Toronto grows ever more sophisticated, and its downtown more affluent, it's inevitable that established residential neighbourhoods will change. But even as revitalized interiors become more and more the norm, the idea of going the full Monty – tearing down an outdated 1920s city home and starting over – can be traumatic for the rest of the street, especially if your dream house is Modernist. This handsome new house in the Roncesvalles area by Altius Architects is a splendid example of how it can be done with sensitivity, but even so, it initially faced considerable opposition.

There's a received wisdom that streetscapes should be consistent, and since whole swaths of the city were built during a feverish period between about 1910 and 1930, many of our downtown streets are lined with houses that are remarkably similar. But since then, pretty much everything else about life in the city has changed radically. It's becoming rare now to find a house that hasn't undergone at least some renovation over its life, from simply upgrading the windows and furnace, to total gut-and-rebuilds that retain nothing of the original but the façade.

"Through the '80s and '90s, the vast majority of our work was adding a kitchen and family room onto the back of the house," recalls Altius principal architect Graham Smith. "It's a reaction to the formal layout of so many traditional homes, with the living room and dining room at the front and the kitchen on the back. But then everyone inevitably ends up in the kitchen, so why do you even need a living room? And the idea of the breakfast nook, with another table 15 feet away in the dining room, is even more absurd."

A house that's only 20 or 30 feet wide can't afford to waste that much space, so the next big wave was to go open-concept. But there are other problems with shoehorning this layout into an old city house: not everyone wants to live with the sound of the TV in the front of the house while they read at the back, for example. Add in upgrading all the mechanicals, adding insulation, and reinforcing a structure that may not have been all that well built in the first place, and the whole process can become prohibitively expensive – before you even start adding wish-list items like a nicer kitchen. All for a house that, apart from nostalgia, has little real historical or architectural value.

As property values continue to skyrocket in the city, homebuyers are realizing that starting over not only makes sense aesthetically, it's financially sensible as well. "It used to be that people thought of apartments or condos as a place to start, then when you could afford it, you moved up to a starter home, then a bigger one," Smith says. "But now, they're thinking of their homes as a long-term investment; a new house significantly raises the value of that investment."

So the question becomes, what kind of a house to build? Most people in our conservative city still opt for familiar traditional styles, with a wide variation in both taste and quality. But both homebuyers and, hopefully, their neighbours, are beginning to accept that there's room for something altogether new.

One of the greatest drivers for contemporary architecture is not merely aesthetic, but practical: its ability to accommodate state-of-the art environmental efficiencies, an issue that can only become more pressing as time wears on. But, especially for a younger generation that may have grown up in a contemporary condo and lives in a city that's increasingly populated by good modern commercial architecture, contemporary design's appeal lies with the freedom it affords. It allows them to design a home that suits the way we live now, rather than adhere to some romantic ideal from a century ago.

In this case, the kitchen is the literal and figurative centre of the house, and the rest of the main floor relates without being completely engulfed by it. The central column that comprises the stairway rises all the way to the top floor, flooding the house with light – a universal need with houses set cheek by jowl with their neighbours. There's a natural progression through the day from the entrance (or the garage set under the house, with its mudroom entry for kids laden with sports gear or snowy boots); to the kitchen or other main-floor seating areas; to the second storey for kids' rooms and den; then finally the top storey for the master suite. Yet the whole house works together; there's no need to concede to conventional divisions.

Still, the most common objection to Modernist replacement houses, and the most difficult to quantify, is an emotional one. People love old houses, and there's a pervasive fear that putting up a slick glass-and-steel box in a row of dignified old Edwardians will be akin to putting up a McDonald's on their street. (And, as with every other form of design, there's just as