A few years after Julian Abele became the first Black designer for Horace Trumbauer’s architecture firm, overseeing such celebrated buildings as Philadelphia’s Parkway library and Harvard’s Widener Memorial Library, he purchased a mahogany-red townhouse at 1515 Christian St. In the early 20th century, his block was known as “Doctor’s Row” because so many Black professionals made their homes there.

Abele wasn’t even the street’s most famous resident. The Rev. Charles Tindley, who presided over a 10,000-member church on Broad Street, and helped write such classic hymns as “We Shall Overcome,” was living a few doors away, at 1509.

When Abele arrived in 1916, the surrounding neighborhood, now known as Graduate Hospital, was the epicenter of Black cultural life in Philadelphia, and Christian Street was its main thoroughfare, according to Evergreens, a neighborhood history by Andrew Dalzell. Interspersed among the fine houses were some of the city’s most important Black churches and Black-run civic institutions. The great concert singer Marian Anderson, who had grown up nearby, bought a house in the neighborhood in 1924. It was her husband, Orpheus Hodge Fisher, another Black Philadelphia architect, who introduced Abele to the French pianist who would become his wife.

If the city’s Historical Commission cared about the meaning of such places, and the contributions of such Black luminaries to Philadelphia’s collective identity, this block, which is believed to date from the 1880s, would have been listed on the Historic Register long ago. But Abele’s house is the only one of the block’s elegant Victorian townhouses that has been protected. It was nominated in 1984 by its owner, Barbara Candia, a longtime resident who acquired four properties on the block during the bleak decades when the neighborhood was losing population. Thousands abandoned the area starting in the ‘60s, when the city announced plans for a crosstown expressway along South Street, but today Graduate Hospital has the distinction of being Philadelphia’s most gentrified neighborhood.

The changes in the neighborhood enabled Candia to cash in on her investment. In the summer, she sold 1513 Christian, which shares a party wall with Abele’s house, to the Stamm Development Group, which promptly applied for a demolition permit. At the time, the three-story building was being used as a boardinghouse, making it one of the last places in Graduate Hospital where low-income people could find a cheap rental. In its place, Stamm plans to erect a luxury condo building, four stories tall, with five units.

» READ MORE: Searching for a new identity, Philadelphia’s most gentrified neighborhood looks to its African American past | Inga Saffron

And now the punchline: Stamm was able to get a zoning permit for the taller, luxury building by paying into a fund intended to increase the city’s stock of affordable housing. Permission for the additional floor will cost the company all of $34,000, according to city planning officials.

Philadelphia’s new townhouses have been growing taller since the city updated its zoning code in 2012, increasing the base height from 35 to 38 feet. But two years ago, City Council introduced a new height bonus to encourage developers to incorporate some lower-priced units into their upscale projects. The goal behind the provision, known as inclusionary zoning, was to retain a modicum of income diversity in gentrifying neighborhoods. But because most developers don’t want to be bothered with the administrative details, the law gives them an out. They instead can contribute to the city’s Housing Trust Fund, which helps support various forms of subsidized housing in the city. The size of the contribution is based on how much extra space the developer gains from the height bonus.

In theory, the height bonus is a great idea. The approach has been used (albeit with some complications) at One Water St. and at 205 Race. Both are large, high-rise developments, and the extra height was barely noticeable. One Water Street’s contribution to the trust fund was also quite meaningful, a hefty $3.75 million. It’s not clear whether Council expected the height bonus to be applied to small, townhouse-sized projects such as the one on Christian Street, where the contribution amounts to little more than a rounding error.

But together with the 10-year property tax abatement (which was just extended to the end of 2021), such incentives are skewing the financial model for development in Philadelphia. With its huge inventory of sturdy 19th- and 20th-century townhouses, the city once excelled at renovations and adaptive reuses of older buildings. Now, zoning and tax incentives increasingly reward teardowns.

It’s true that you can get a tax abatement for renovating an old house, but only for the increase in the building’s property assessment. New houses receive the abatement for the entire value of the building — a much better deal. Why undertake a tricky renovation when new construction is so heavily subsidized? The teardown on Christian Street is “an example of the law of unintended consequences,” observed Paul Steinke, director of the Preservation Alliance.

Bundled together with those incentives, the inability, or perhaps unwillingness, of the Historical Commission to designate more properties has created the perfect storm for demolitions.

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In another place and context, Stamm’s design would hardly rate a mention. The modern, black-and-white composition is no worse than many new townhouse designs; it might even be a notch above average because it appears to have brick on the facade. But the damage on Christian Street would be substantial. Located roughly in the center of a row of warm-hued Victorians, it would cleave this legacy block in two.

No one at Stamm Development group responded to my inquiries, and the architect for the project is not identified on the company web page. In the renderings that appear on the site, the proposed condo building swaggers like a miniature skyscraper, towering over its neighbors. Its central bay seems intended to function as a kind of spire — like a miniaturized version of the mast on Norman Foster’s Comcast Technology Center.

It’s hard to tell whether the proportions in the renderings are accurate. Stamm’s design is so oblivious to the block’s history that the computerized renderings mistakenly substitute a pair of Brooklyn-style brownstones for the plainer Philadelphia townhouses that exist now on the block.

Just to be clear, it’s not the height of Stamm’s project that’s the real problem. Although there are some wonderful ensembles around the city, many rowhouse blocks in Philadelphia have staggered rooflines. If sensitively designed, Stamm could easily add another floor — or two — to the existing house without causing any visible harm. According to Candia, whom I interviewed from the sidewalk while she stood at the top of her steps, 1513 is in good condition. It also has a deep rear yard.

It’s not too late for Stamm to do the right thing. The company has not yet obtained a construction permit, or even sent off its check to the Housing Trust Fund. Renovating this house, and helping to preserve the distinctive character of this historic block, would be a far more meaningful contribution.

While researching this column, I received a call from Peter Cook, a Washington, D.C., architect who is Julian Abele’s great-grandnephew. Cook, who grew up in Detroit, the son of a federal judge, would always walk down Christian Street when he came to visit relatives in Philadelphia. “It gave me chills to know I was related to someone who designed such wonderful buildings,” he said.

It should give us all chills to know that Julian Abele’s historic block has survived this long — and could soon be lost.

NOTE: Because of a mistake in the city’s Atlas database, an earlier version of this story incorrectly stated that Barbara Candia obtained the demolition permit for 1513 Christian Street. It was Stamm Development Group that applied for, and received, the permit.