The three-decker is like a snowflake; there are no two that are exactly the same. To the untrained eye, all three-deckers may look similar, but we in Dorchester know that each one is different in its own special way. The view down a three-decker lined Dorchester street is pretty much the same today as it was 100 years ago, the pillars of the front porches lined up like a row of columns in a Greek temple.

A closer look reveals the variety within the pattern. The columns are square, round, fluted, tapered, truncated, or elongated, and topped with capitals, Doric, Ionic, or Corinthian. The porch railings at each house might have a different geometric design centered in the balusters. And behind the porches, the house fronts are single bay, double bay, or flat.

Another key feature is the roofline, most often a thick soffit with frieze board and dentals. Sometimes the roof has a false pediment, mansard, or cone-shaped gable. There is all variety of plinths, lintels, window trim, corner boards, casings and shingle treatment. The major vocabulary for ornament on three-deckers ranges from the Classic to High Order Queen Anne.

However three-deckers may vary, there is one thing that they all have in common, and that is people. Think of the humanity that has come and gone through Dorchester three-deckers since they were introduced to the neighborhood in the 1870s. It is impossible to know the number of immigrant families who set up house in a three-decker as they struggled to achieve the American dream.

Originally built to accommodate the immigrant population flooding into Boston during the mid-to-late nineteenth century, the three-decker was coldwater-flat housing for the Irish and other newcomers, primarily from Europe. Today, all corners of the globe are represented and people from Vietnam and Cape Verde to the Dominican Republic now reside here and inhabit the houses. Another new group is the professional class, whose members enjoy the close proximity of Dorchester to downtown Boston. Dorchester was once exclusively blue collar, but now it has many residents who are making lots of money.

Most immigrant families had come from small houses and cottages with only a couple of rooms. In their new three-decker home, each floor had a sprawling layout of five and six rooms, designed this way because the Irish and Italian immigrants tended to have large families. Nowadays, for some people, especially those who grew up in suburban single-family homes, the concept behind the three-decker is difficult to grasp. How could one house contain three different homes?

There is something pleasing about the scale of a three-decker: Its proportions relate to the pedestrian on the street, yet inside there is privacy, with bedrooms placed at opposite corners and separated by common areas. And there is the notable scale of workmanship; the three-decker is a totally handmade object. It is a real old-fashioned lath and plaster affair, with every piece of wood, inside and out, cut by hand and fit with care. Building a three-decker was labor intensive, and the new immigrant population provided developers with a source of workers that was inexpensive and practically limitless.

Three-deckers were built for economy and developers would do an entire area and then move on until Dorchester’s streets were packed with them. Some neighborhoods were zoned this way, and with a minimum lot requirement of 5,000 square feet, the three-decker was allowed, as of right, to be built without zoning relief. In a registry of properties now being compiled, early estimates show that there are approximately 26, 500 three-deckers throughout the city of Boston.

The typical three-decker comes with a few basic floor plans. Hallways are single-loaded, with the rooms off one side; or double-loaded, the so-called railroad apartment, where the hallway runs down the middle like a freight train. There are some plans where there are no hallways at all, and the circulation path crosses almost every room. In the oldest buildings, the bathrooms are located on the landings at the back stairway.

The standard-size footprint of a three-decker is 20 feet by 40 feet. The rough framing is done in two ways. In balloon framing, the studs that make the walls extend from the foundation to the roof, with the floor joists suspended in the middle. In platform construction, one level is built at a time, with the floor joists set on top of the wall studs for each level.

These houses are freestanding structures that allow for window openings to be cut into the sidewalls. This was an improvement on the shared sidewalls of early tenement houses, where every apartment had only a few windows in the front and back. The average three-decker has about 50 windows that open in the summer to create a cross ventilation through the rooms; they also bring warmth and sunlight, and chilly winter drafts.

Some three-deckers are spaced very closely together, which can make for awkward situations. As, for instance, when the bedroom window of one house is placed directly opposite the kitchen window of another, in which case a man may rise from bed and throw open the window to greet the morning sun, only to find his next-door neighbors sitting at their kitchen table, munching Corn Flakes.

Back in the day, every three-decker dining room had its own stained glass window, and along the sidewalk, a well-tended privet hedge framed the steps of the front porch, where a nearby rose bush was ubiquitous. In the future, the Dorchester three-decker will be prized more than ever, and city dwellers will continue to cherish it as the perfect place to live – if only the people upstairs wouldn’t stomp around so much.

With special thanks to Buddy Christopher.