Portions of Deer Park United Church in Toronto were demolished in January, 2017. Fred Lum/The Globe and Mail

Bishop Strachan would sit bolt upright in his grave if he could see what is happening to the old Deer Park United Church. John Strachan was the first bishop of Toronto, a stern figure often pictured in flowing clerical robes. In his time, the pious city that came to be known as Toronto the Good was putting up churches left and right.

Today, it is turning many of them into condos. Across the city, developers are buying up old churches and making them over as high-end residences. The combination of two trends – rising property prices and falling church attendance – has produced a whole new real estate category: the church conversion.

Deer Park United is becoming part of the Blue Diamond Condominiums at Imperial Plaza, "an address of distinction nestled in the exclusive Forest Hill neighbourhood." Builders have already torn down most of the 1913 church at St. Clair Avenue West and Avenue Road. Demolition machines clawed at its heavy stone walls, leaving piles of rubble that made Deer Park look like a bombed out church in Normandy after D-Day. All that's left is the church tower and the empty front end of the building, open to the elements at the back like a hospital gown.

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Parts of Deer Park United Church are being incorporated into the new Blue Diamond Condos on St. Clair Avenue West in Toronto. Camrost Felcorp

"It's kind of like going to a cemetery and seeing a headstone – it's a historical marker, but the spirit is gone," says the minister of Deer Park United, Rev. Deborah Hart.

Crews are digging a big hole behind the church for the foundations of a 26-storey steel-and-glass condo tower. What remains of the old building will frame an outdoor courtyard with a glassed-in restaurant. An artist's conception shows sleek young condo people chatting next to a gleaming bar. A surviving stained-glass window glows above them.

Prosecco in place of prayers. Yes, the bishop would be startled, all right. His Toronto was a God-fearing city. One study found that from 1845 to 1893, when church building was at its peak, about 90 churches rose in the city centre south of Bloor Street. Toronto built all manner of churches: red-brick churches and limestone churches; Romanesque-style churches and Gothic Revival churches; Protestant churches and Catholic churches; chapels and cathedrals.

But keeping the pews full and the roof from leaking is a challenge in today's more diverse, less godly Toronto. Attendance at Protestant churches in Canada started declining in the early 1970s. The United Church, the country's largest Protestant denomination, saw the number of congregations drop by 579 from 2005 to 2015. Another 60 have been lost since 2015, bringing the total remaining to 2,834.

Many churches close their big front doors for good because, with dwindling, aging flocks, they can no longer afford the upkeep. Deer Park packed up in 2008 after its next-door neighbour, Imperial Oil, moved its head office to Calgary and stopped supplying heat to the church. After emotional discussions among the congregants, some of whom had been going to Deer Park since their Sunday-school days, the church sold to a developer for about $4-million. They gave three quarters of the money to charities and kept the rest as a nest egg.

Carrying the church cross and other treasured objects, congregants marched in procession to their new home a few minutes away: the Calvin Presbyterian Church. The two congregations already worshipped together in summertime, so they co-habit nicely.

In some cities, a deconsecrated church such as Deer Park might have been torn down for a parking lot, used to house a weekend flea market or just left empty and abandoned. Around the world, churches have been converted into theatres, bookstores, artists' studios and yoga spaces. In Detroit, one old church now serves as a craft brewery.

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A Catholic church in Hungary even became a strip joint, drawing a sharp protest from Rome.

But the soaring Toronto real estate market of recent years has made Deer Park and other churches tempting targets for condo builders.

The new Blue Diamond Condos in Toronto maintains the facade of the historic Deer Park United Church. Camrost Felcorp

Most of the vacant lots, parking lots, old lumber yards and other obvious places to put a new building have already been snapped up. Developers are desperate for property to build on. Churches own a lot of it, especially in the coveted central city.

A 2013 study by Jason Hackworth, a professor of geography and planning at the University of Toronto, found 23 churches that had been turned into residences of some kind, with another 10 projects under way.

On High Park Avenue in the west end, developers built a condo tower right on top of an empty church. The Third Church of Christ, Scientist held services from 1928 till 1999, when its congregation disbanded. The new owners preserved the church's atrium, with its terrazzo floors and art-deco plasterwork. Visitors can still see the motto "Thou Shalt Have No Other Gods before Me."

A few minutes away on Annette Street, four stately churches stand within blocks of each other. Two have already gone condo and a third is going. The developer of 260 High Park is converting a 110-year-old United Church and adjacent Sunday school building into "an exquisite collection of Tribeca-style lofts, modern condominiums and townhomes."

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On the other side of town, near Pape and Danforth, a developer built loft apartments in the cavernous Riverdale Presbyterian Church, which was built in 1912 and expanded in 1920. Profit from the condo deal went into fixing up the Sunday-school wing so the congregation could worship there.

All of this has to give churchgoing folk a queasy feeling. It is one thing to break off church property for seniors homes or affordable housing, as quite a few churches in Toronto have done. It is another to transform them into playhouses for the rich.

In 2016, the chief executive of a bank put his townhouse unit in a converted Rosedale church on sale for $4-million, Toronto Life magazine reported. It had heated marble floors and a spiral staircase. Deer Park's Blue Diamond advertises a lifestyle "steeped in heritage and embellished with luxury." It is a far cry from Boy Scout meetings and ladies' teas in the church basement.

Some say church conversions are part of a relentless urban upscaling that leaves ordinary people outside the charmed circle. In a 2013 paper on church conversions that he chose to title Altared Places, Memorial University professor Nicholas Lynch decries the "secular embourgeoisement of the central city, a process that increasingly remakes the city as a place of capital reinvestment, middle-class colonization and social upgrading."

On the other hand, it is not clear what else to do with abandoned or underused churches. Many congregations have tried to fend off financial collapse by renting out space for dance classes or drama rehearsals. It is seldom enough to pay the bills.

Converting churches often saves them from demolition. As sad as it is to have church organs fall silent and altars carted away, it would be sadder to see these grand buildings erased from the city streetscape altogether – or left as decaying monuments to the past.

When churches go condo, developers usually bring in heritage architects to preserve their best features. Even without a religious function, they are still a lovely sight. Many people are drawn to church conversions because, with their stone interior walls and wood beams, they offer more character than a glass box in the sky.

Toronto's vocal heritage and neighbourhood groups have fought hard to save churches. Deer Park's front end, at least, has been preserved because the city gave it a heritage designation, recognizing its cultural and architectural value.

Times change. Cities change. The church once served a certain purpose: as a place of worship and a community hub. Now it will serve a new purpose: as a place to live and to gather. It may be over espressos or martinis instead of hymns and sermons, but people will still congregate in a fashion.

Ms. Hart, the Deer Park minister, notes that her church is not averse to raising a glass. It offers wine as well as grape juice at its services. So "maybe when it's open we'll go over and have a drink and make a toast to history."