GALLERY: 
Row house, town house, brownstone
Confused by what's what? Here's a primer on the buildings that help define Boston
It is a question that has vexed real estate brokers and lovers of urban architecture for generations: What's the difference between a town house, a row house, and a brownstone? Boston native Kevin D. Murphy, whose book ''The American Townhouse" will be published in November, defines each:
Town house: A multistory urban house, attached or detached, that is built close to the street and scaled similarly to surrounding houses.
Row house: A multistory urban house built in a style that is consistent with, even replicating, that of adjoining houses; often built by the same architect and developer.
Brownstone: Any of the above structures whose façades are sheathed in brown sandstone.
So town house is an overall term, row house a subset of that, and brownstone a further subset of both.
''Town houses were often designed to be unique," said Murphy, who teaches art history at the Graduate Center of the City University of New York. ''But row houses strove for consistency. Sometimes sameness is boring, but sometimes it gives the streetscape a unity, instead of each building doing its own thing. And the term brownstone is simply about material, although in New York it's come to mean any row house built before 1910 as a single-family home."
Classic bow-front or bay window row houses give Boston one of its most iconic images: a streetscape of perfectly proportioned red brick buildings receding into the distance, perhaps punctuated by a church steeple. The bow and bay windows are not unique to Boston, Murphy explained, but are more common in Boston than anywhere else. He credits British architect Robert Adam's influence and the fact that the idea of a ''house on a park," originally developed in London, found an especially eager following in Boston, encouraging windows that allowed for better views. Further, city fire codes actually encouraged such subtle ''projections" from a building's main façade.
But beyond the shape and configuration of the front windows, there are many other architectural elements that mark the town house/row house/brownstone triumvirate: oriel windows, which project out from the façade but do not touch the ground; copper accents that have weathered to a rich green hue; effusive ornamental ironwork, usually painted black; interior double parlors to bring light into a long and narrow space; and the Italian concept of piano nobile, the placing of the primary living space on the second level above what were the kitchen and other service areas.
''This is the main level for eating and entertaining," said Joan Cucchiara, of Boston real estate brokerage Otis & Ahearn, as she walked through a 1828 Federal-style town house on Beacon Hill currently listed for $2.98 million. ''This is very characteristic of Beacon Hill town houses."
The Federal style sought to bring the spare classicism of Roman architecture to the service of the new American republic. Being an early example of this architectural restraint, the house on West Cedar Street has a flat façade and fairly constrained interior spaces.
But following this initial Puritan reticence, Boston town houses soon became richer and more architecturally complex. Charles Bulfinch, architect of the Massachusetts State House, first introduced the bow front to Boston with houses on Beacon Hill's Louisburg Square in the late 1820s, borrowing the gesture from English architect Robert Adam.
''The bow front provides light from different directions," said Murphy. ''It also gives interior spaces more interesting shapes."
It was in the South End that the bow front became a signature design element. Five Union Park is a quintessential example, on a street that Michael Doherty, partner in Citylife Real Estate, calls ''the Louisburg Square of the South End. When Union Park was being laid out, the Back Bay was just being filled in. This is where most prominent people of the time were building houses."
Like most South End row houses, 5 Union Park was built originally as a single-family home, only to be carved up later into multiple apartments. Now being offered at $2.995 million, it features a 2,000-square-foot ''owner's duplex" on the first two levels and three income-generating apartments above.
''The apartments can generate as much as $9,000 per month in rental income," Doherty said. Nonetheless, he's showing a number of row houses to prospects who plan to let the leases run out and occupy the entire building.
By the time Back Bay was filled in and beginning to eclipse the South End in prestige, a cornucopia of architectural styles was competing for the attention of urban homebuilders.
One particularly effusive example is the Converse mansion at 348 Beacon St., a brownstone built in 1886. Bow and oriel windows dominate the façade, and in keeping with the Queen Anne style popular at the time, elements are borrowed freely from numerous architectural periods. But it was not all about style: As architectural historian Bainbridge Bunting has pointed out, Back Bay regulations enacted in the 1870s called for the main façade of a structure to be set back 20 or 22 feet from the property line. But, Bainbridge wrote in his book ''Houses of Boston's Back Bay": ''The owner was permitted to construct such appendages as steps, porches, and bay, oriel and bow windows."
Farther up Beacon Street toward the State House, broker Tracy Campion of R.M. Bradley walked through one of the five units in a town house at 50 Beacon.
''The large bow window allows you to see up and down the street, and many people are willing to pay a premium to be on a corner lot," she said. Typical of the hodgepodge design of the 1880s, the building is brick with brownstone accents, meaning it doesn't qualify as a ''pure" brownstone under historian Kevin Murphy's criteria.
Nicholas Tranquillo's Commonwealth Avenue town house doesn't qualify either, because its original 1879 Peabody, Stearns brownstone façade was altered in 1917 by architect Harleston Parker to a more Federal design. Since acquiring the property in 1972, Tranquillo has seen the town house market reach its current stratospheric levels.
''People tell me, 'Sell the damn thing. It's worth a fortune, and you can go anywhere,' " said Tranquillo, a retired Boston public school teacher. ''But I enjoy my tenants and I enjoy fixing up the place. It's very baronial. I feel like a king here." 
