A brownstone building is one composed of, well, brownstone—a black sandstone quarried mostly in New Jersey, Connecticut, and Maine. Because this stone is soft (in stone terms) and easy to cut, it lends itself to intricate embellishment, making these properties highly sought-after in real estate today.

Brownstones are three- or four-story row houses that can be found in New York City, Boston, Philadelphia, and other Northeastern cities. In addition to intricate moldings, pediments, and other decorations, they generally have a stoop, with steps leading up to an elevated front entrance, where residents can sit and converse with passing neighbors.

Brownstones are among the most identifiable American architectural icons, especially when it comes to movies set in New York. In "Breakfast at Tiffany's," Holly Golightly sung "Moon River" from the window of a brownstone; in "Sex and the City," Carrie Bradshaw tripped up and down the steps of one. While those brownstones were in Manhattan, Brooklyn-based brownstones may be seen in films like "Moonstruck" and Spike Lee's "Crooklyn." (Incidentally, the "Crooklyn" brownstone sold for $1.7 million in 2013 and is likely to fetch considerably more today.)

Why are brownstones in such high demand?

Brownstone became famous as a building material in the mid-nineteenth century as a less expensive alternative to limestone, granite, and marble. According to Jack Pontes, a professional craftsman, conservator, and owner of J. Pontes Brownstone Restoration, most of the brownstone quarries have been depleted. As a result, brownstones are increasingly difficult to obtain, increasing their value; many also have historic or landmark designations.

"You'd be hard pushed to find a brownstone for under $2 million in the finest Brooklyn areas," says Lesley Semmelhack, an associate broker with the Corcoran Group. "It's the pinnacle of real estate." You're aware that you're sitting on something incredibly exceptional and important."

Because of the popularity of brownstones, many buildings are referred to as brownstones that are not. The majority of these imposters replicate the architecture, such as the stoop, but have standard red or yellowish brick facades. True brownstones have a sandstone facade that is brown or pinkish-brown in color. (You can have traditional brick on the sides and back of the house as long as the front is brownstone!)

Brownstone maintenance

Brownstone is a gorgeous sandstone, but its porous and layered nature makes it sensitive to the elements. It deteriorates over time because of freezing and thawing, salts, and air pollution. It can be expensive to restore and repair it, especially when done well. A hasty patch job might be glaringly visible.

Building owners can slow the degradation by properly maintaining their structures. Clearing gutters, addressing roof leaks, removing climbing ivy, filling open joints, covering ledges and other projections with metal (flashing), mending missing mortar joints (repointing), and cleaning thoroughly are all recommended by the New York Landmarks Conservancy.

The scarcity of brownstone in quarries also presents a problem for brownstone owners looking to rebuild their façade. Damaged portions cannot simply be patched with fresh brownstone. Even if you could, the stone's color fluctuates depending on which quarry it originated from.

Pontes smashes some original brownstone and blends it with cement and colors it to match while restoring brownstones. He claims that original brownstones are frequently discovered at demolition sites, buried beneath the pavement. He collects it whenever he can and preserves it for repair initiatives.

The advantages and disadvantages of owning a brownstone

Is it therefore worthwhile to purchase a brownstone? Pontes thinks that they were built with such quality craftsmanship is "always an advantage" in any situation.

Stonework clearly demonstrates the high level of training that was common among craftsmen of the era. The structural quality of the structure is therefore excellent, despite the fact that a homeowner might have to perform some restoration work on the property.

Pontes claims that this is what makes the property special. "In the long run, it's going to be a good value." He likens it to being the proud owner of a diamond or some other priceless gem: "A diamond's value can never be diminished, no matter how many times you polish it."