When trading up isn’t an option, Philadelphia rowhouse owners build up | Inga Saffron

Laurent Hedquist was single, and just starting his career as an architect in 2005, when he bought a two-story rowhouse in Bella Vista. Although it was small by American standards — about a thousand square feet — he felt like he was swimming in space. He even converted one of the house's three tiny bedrooms into a closet.

Then, two years ago, Hedquist got married. A baby followed, along with the usual complement of toys and child-rearing equipment, and Hedquist soon discovered how cramped a Philadelphia rowhouse could be. Even though he couldn't afford a bigger house in the neighborhood, he was determined to remain in Bella Vista, which is part of the coveted Meredith School catchment. So, rather than trading up, he decided to build up, by adding a third story to his classic, two-story rowhouse.

These vertical additions, sometimes called "overbuilds," have always been a staple of rowhouse life in Philadelphia. But thanks to a decadelong boom in the real estate market and a change in the zoning code that allows taller houses, homeowners have embraced the overbuild with a vengeance. So many third-floor additions are popping up (literally), according to builders and neighborhood groups, that they are starting to change the look and economics of what was once Philadelphia's most affordable housing type.

You can find overbuilds all over the city, but the majority have been concentrated in a relatively small geographic area: the affluent neighborhoods near Center City. As it gets harder to find a reasonably priced home in places like Rittenhouse, Fitler Square, Bella Vista or Graduate Hospital, buyers are more willing to crowd into two-story homes, which are generally located on narrow, secondary streets. By adding a floor (or two), they can effectively manufacture additional real estate out of thin air.

For the most part, the overbuild trend has been good for the city. Large suburban homes are still the norm in America, and overbuilds help Philadelphia compete by making it possible for people to continue living in the city as their families grow. Overbuilds also serve the cause of preservation, since developers are less likely to demolish Philadelphia's handsome, brick rowhouses if they can expand them to a more marketable size. Think of them as a gentle form of densification.

Outfitted with suburban-scaled kitchens and master suites, a few of those formerly tiny rowhouses are now worth as much as $1 million. Hedquist's project isn't that grand, but it will turn his 19th-century workers' house on Fulton Street into a comfortable, four-bedroom, two-bath, 1,425-square-foot home. He'll get an office, and his wife, Abigail, will have room to set up a painting studio.

Once the first overbuild appears on a street of two-story homes, they tend to go viral. There were already four overbuilds on Hedquist's block of Fulton when he started working on his addition. To his surprise, his next-door neighbors not only embraced his plan, they asked Hedquist to design a twin for their house. By combining the projects and hiring the same contractor, the two families got a break on the price. Now several other neighbors are talking about adding third stories, says Hedquist, who expects to spend $165,000 on his overbuild.

By the time everyone is done, the 700 block of Fulton Street will be unrecognizable. Located just north of the Italian Market, its two-story houses were built for immigrant families. The homes, which squeezed three, minuscule rooms onto the second floor, were the Philadelphia equivalent of New York's tenement apartments. Because the block was built by a single developer, the houses were originally identical — the same height, the same cornice details. Such ensembles are one of Philadelphia's defining architectural features.

But not for long.

No one in the city has a good handle on how many overbuilds are going up. But Phil Katz, a developer-contractor who named his company 3rd Story Philly, says he is getting three or four requests a week from homeowners. He has overseen about eight additions, including his own in Bella Vista, since his website debuted two years ago.

Increasingly, the calls are coming from Port Richmond or Brewerytown. Home prices in those neighborhoods are generally too low to justify the investment in a third story, Katz says. But who knows? As more people get priced out of Philadelphia's core, they are swarming into lower-priced neighborhoods.

Things are different in Fitler Square, where the median sale price last month was $848,000. After buying a 1,200-foot house on Pine Street for $670,000 last year, Kyle and Kate Wharton invested $300,000 to expand it to 2,100 square feet. That seems like an astonishing sum for a workers' house. "We wanted to be in the Greenfield School catchment," Kyle Wharton explains, "but I'm sure we'll get our investment back."

One of the biggest issues with overbuilds is the way they look. Even though the 2011 zoning code increased the basic rowhouse height to 38 feet, the city still requires most third-floor additions to be set back eight feet from the front of the house. The rule is based on the notion  that pedestrians shouldn't be able to see the overbuild from the street as they walk by.

But why? Philadelphia has plenty of three-story rowhouses, and developers who build new houses aren't required to set back the third floor. What is the logic for pushing back the new structure, especially in neighborhoods that aren't part of a historic district? The rule certainly hasn't promoted the cause of good design. Because a setback is generally used as a roof deck, the typical overbuild ends up looking like a country shack that was airlifted onto the top of a rowhouse. In some overbuilds, the window placement seems to be almost arbitrary. A simple mansard that comes to the front of the house is almost always better.

"They've created all these weird rules to follow," agrees Kevin Brown, the chair of the South of South Street Neighborhood Association. "We've been all disappointed aesthetically with the way the setbacks look."

The setback requirement also eats up a lot of useful space. If you're going to go to the trouble and expense of adding a third floor, Hedquist argues, you want to maximize your square footage. He petitioned the Zoning Board for a variance to dispense with the setback. By raising his 22-foot-high house to around 36 feet, he was able to fit a master bedroom, a bathroom, and a small office on the third floor. Like most people who add third stories, he is installing a deck on the roof, with a pilothouse enclosure for the stairs.

Because Hedquist is an architect, he understood instinctively what it would take to create a gracious overbuild design: Respect the cornice. Establish good proportions. Use quality materials and appropriately scaled windows. The design he came up with is a modern version of a 19th-century mansard roof, with a gently sloping bay. It's the kind of design you see on the grand houses along Pine and Spruce Streets.

It fits his old house so well that his overbuild should look as if it had always been there.