There's nothing fancy about the ensemble of redbrick houses that line the 3600 block of Lancaster Avenue in Powelton Village. Built in the late 1870s, when the avenue linked country farms to city markets, the modest, wood-trimmed buildings housed working people who tended shops on the ground floor. Folks still live upstairs today, and neighborhood businesses - bike store, nail salon, day-care center - still pepper the storefronts below.

Such blocks are what make Philadelphia, well, Philadelphia.

So why is this intact and fully occupied ensemble being targeted as a teardown?

Last week, the Powelton Village Civic Association learned that the owner, AP Construction, was interviewing demolition contractors in preparation for selling the block-long row of houses it calls Lancaster Mews. Given the swirl of construction two blocks east on Drexel University's campus, the assumption is that a buyer will "tear it down and replace it" with student housing, AP's head of development, Bob Gillies, told me.

And there goes another functioning, attractive, meaningful patch in the city's great quilt of buildings.

There is nothing to stop AP or the next owner from razing Lancaster Mews or almost any other building in the neighborhood. Powelton Village may be a riot of architectural treasures - elegant Victorians, Italianate villas, lacy Queen Annes - yet most buildings, Lancaster Mews included, have no historic protection. A civic association plan to create a neighborhood conservation district, a less-restrictive version of a historic district, has been sitting on a shelf for two years while Councilwoman Jannie Blackwell contemplates whether to sign off on the proposal. That's councilmanic prerogative.

Meanwhile, developers have discovered they can make a tidy sum simply by replacing one of these old houses with a stucco-clad apartment building and then cramming it with students. Assuming that the project meets the zoning code's 38-foot height limit, all that's needed is a building permit.

The presence of large numbers of students in Powelton Village is certainly not new, but the pace of these teardowns is. In the past, developers would just convert a large house into apartments. But they've discovered that a building with a modern layout can house more people, especially if you dispense with such quaint inefficiencies as a front porch or patch of lawn. If they make the ceilings low enough, they can even fit a four-story building onto the site.

More than two dozen homes have been lost in the last two years in Powelton Village, located west of Drexel between Spring Garden and Lancaster. These dreary, mini dorms are now popping up in nearby West Powelton and Mantua, replacing the modest rowhouses that have long provided affordable housing for low-income families. When a one-room student apartment can rent for $600, "many families get outbid," said Kira Strong, who works on housing issues for the People's Emergency Center, a nonprofit community development agency.

This assault on neighborhood housing is happening, oddly enough, just as Drexel and Penn are finally starting to pull their students out of the neighborhoods by building more on-campus housing. Drexel is wrapping up a massive, 24-story tower at 34th and Lancaster that will bring its tally of new dorm beds to 3,200. Penn will complete a 350-bed dorm on Chestnut Street next year.

For all their efforts, the universities can't seem to compete with the private developers who build cheap, frill-free housing that can rent for $100 a month less than campus dorms. The same scenario is playing out near Temple University. There, as in West Philadelphia, many of the ticky-tacky boxes are being built by University Realty, a developer based in Bucks County.

The company began pursuing the student-housing niche about five years ago. The 10-year property-tax abatement for new construction makes teardowns more financially attractive than conversions. You get more rental income and reduce your tax bill to almost nothing. Why bother to renovate an old house?

While the pattern may resemble what is happening in the city's other rebounding neighborhoods, the construction frenzy in West Philadelphia is having the opposite effect. Instead of stabilizing and improving the area with single-family homes, mini dorms make them less viable as neighborhoods.

Powelton Village has been struggling for years to maintain a core of owner-occupied houses. When Drexel and Penn finally owned up to their destructive ways, and began building more on-campus housing, the neighborhood looked as if it might make a comeback.

Now, along with West Powelton and Mantua, it seems fated to be a student ghetto. "We're really concerned," said Drexel's Bob Francis, who oversees the university's construction. "Everything we're doing as an institution is to restore the fabric of the neighborhoods, especially on the Lancaster corridor."

Where's the Nutter administration on all this, you might ask? Planning Director Gary Jastrzab said he sees a conservation district as the best way to control indiscriminate teardowns and protect the neighborhoods. The problem is when the district council member - in this case, Blackwell - won't act.

So, as a stopgap, Powelton Village Civic filed papers this week to designate Lancaster Mews as an individual historic building. Drexel and the Planning Department are supporting the nomination. That should carry weight with the Historical Commission, though you never know. Like other city agencies, it has been very developer-friendly.

New development has been good for Philadelphia, reinvigorating tired neighborhoods. But if we keep losing blocks of fine, textured buildings like Lancaster Mews, there will be no neighborhood left to revive in Powelton Village.