OLD CITY The Shirt Corner and the Suit Corner buildings had been through a lot during their nearly 200 years at Third and Market Streets, but somehow they always found a way to adapt. Only two months ago, the two were still inseparable companions, still standing eyeball-to-eyeball, still trying to outdo each other with their blazing, red-white-and-blue facade graphics.

Today, the Suit Corner, on the southwest corner, is a smoldering ruin, its roof gone, its timbers charred black from Wednesday's fire. The Shirt Corner, on the northeast corner, is a hole in the ground. It collapsed March 13 as construction crews were taking it apart on orders from city officials, who deemed it a hazard.

Many are wondering how it is possible for one of Philadelphia's most vibrant neighborhoods to lose two historic corners - eight buildings in all - in a matter of weeks.

Philadelphia certainly has plenty of derelict and depopulated neighborhoods where old structures regularly fall to neglect and fire. But Shirt Corner and Suit Corner were surrounded by popular restaurants, boutiques, antique shops, and high-end condos.

The Old City neighborhood is also one of 15 historic districts under special protection of the city. Since receiving that honor in 2004, it has lost at least four other significant structures, two to fire, two to neglect. One of the fire victims, Friedman's Umbrella, sat next door to Suit Corner. Another, the Five Spot dance club, was around the corner on Bank Street.

"What is it about Old City?" asked Ellen Yin, who owns two top-ranked restaurants, Fork and High Street. Situated two doors west of Suit Corner, they had to shut for two days to be cleared of smoke and dust. (The fire's cause has not been determined.)

"There is such opportunity here," she said. While Old City's rents could not compare with Center City's, she said the area was quite desirable, and getting more so all the time.

A Historical Commission official agreed, saying the agency was now reviewing one or two renovation projects every month. "Old City is getting developed like crazy," he said.

Yet stubborn examples of blight persist.

This is not the blight of abandonment, Yin said. Suit Corner was a going business when flames were spotted licking at its third story. Although Shirt Corner had been empty since 2009, a new owner was planning to convert the linked buildings into apartments. Alterra Property Group said it had no trouble signing up a CVS as its ground-floor tenant.

It was not until renovations had begun that Alterra discovered what bad shape the buildings were in. As workers peeled away drywall, engineering consultants discovered wide cracks in the brick walls of the buildings, which had been built in the early 19th century to serve the busy docks then at the foot of Market Street.

Because Old City was, as its name suggests, one of the first areas settled in Philadelphia, its buildings tend to be decades older than others in Center City. Even so, Joe Schiavo, a civic activist, said he did not believe age alone explained why so many Old City buildings were in such poor condition.

Rather, the common thread is that Old City buildings tend to be owned by individuals or families, who inherited the properties.

They did not set out to own large, mixed-use commercial buildings. Many owners are elderly, and some are simply hanging on, "waiting it out till someone scoops it up for big bucks," Yin said.

In contrast, many large commercial properties on the west side of Broad Street, in Center City's commercial heart, are now owned by property management companies, some local, some national.

Yin, who just took over A. Kitchen in a renovated early-20th-century tower at 18th and Walnut, argued that those owners see maintenance as their core business and a way of preserving value. As large companies, they also have easier access to capital for improvements and to the professional skills needed to execute them.

A walk down Old City's two main commercial streets, Second and Third, makes the problem clear. Even when buildings are fully occupied, with ground-floor shops and residents upstairs, they frequently look as if they need a top-to-bottom renovation. Some show bulges, a sign that the facade is in danger of separating from the supporting structure. Many brick facades are in dire need of pointing, and windows have been covered in plywood.

To Rich Thom, an Old City architect and activist, ownership is just one part of the problem. He blames officials at the Department of Licenses & Inspections for poor enforcement. Even when inspectors do cite owners for building violations, Thom said, he sees little follow-up.

That's one reason, he said, that such iconic buildings as the Samuel Machinery Co., at Third and Cherry, and the "Indian Affairs" building at 223 Chestnut St., next to Jose Garces' celebrated Amada restaurant, were allowed to decay in full public view. Both are now slated for renovation, but only after years of complaints from residents and preservationists.

Graham Copeland, who runs the Old City Special Services District, insisted that the problem is not as bad as Thom suggests.

Those two examples "are isolated situations," he said. "These are things that happen with older buildings."

By Thom's estimate, nearly 15 percent of Old City's buildings are not properly maintained. Few have sprinklers or other effective means of fire suppression.

"We keep increasing the number of historic buildings in Old City," he said. "But what are we doing to protect them?"

@ingasaffron www.inquirer.com/built