If ever a housing type has suffered a bad rap it is the English back-to-back. 

Largely swept away as part of 20th century slum clearance, barely a single house of this type survives in most of the the UK’s northern industrial cities that used to be famous for them. There is nonetheless one place where the form not only survives, but is extremely common: Leeds, the city at the heart of Britain’s fourth-largest metro area.

Essentially, a back-to-back is a terraced house (known as a row house in the US), but with shared walls on either side and to the rear, leaving only one front wall for all the windows and the front door. Rooms within are stacked on top of each other, leaving an entire dwelling with just a single aspect. Many had just one room per floor.

Greedy Victorian developers loved them because they were cheap to build and super dense — with no additional yards or alleys, they used less land as well as fewer materials such as bricks or drains. Early examples had virtually no sanitation and easily turned into diseased death traps.  Yet despite their obvious limitations, the remaining structures are increasingly cherished. And as new developments around Britain show, they might even be making a comeback.

It may seem hard to believe now given the negative reputation they have developed over the years, but the back-to-backs were initially introduced as an improvement on what came before — court housing, a notoriously cramped and lightless type of dwelling which, from the late 18th century, spread like a pox across the metastasizing cities of the Industrial Revolution. Court houses featured a form of back-to-back layout — an outward facing row of houses gave way to a concealed inner yard where further homes were arranged facing inwards. Often with just floorboards over open sewers, shared standpipes and earth closet toilets in their filthy courts, these building complexes built for tens of thousands of urban factory workers were quite literally crap housing. They were partly what Friedrich Engels had in mind when he wrote about Manchester’s scandalously squalid living quarters, where death rates were far higher than for conventional housing. He argued that this amounted to “social murder.”

“We must admit that 350,000 working-people of Manchester and its environs live, almost all of them, in wretched, damp, filthy cottages,” he wrote, “that the streets which surround them are usually in the most miserable and filthy condition, laid out without the slightest reference to ventilation…no cleanliness, no convenience, and consequently no comfortable family life is possible.”

Engels’ perspective wasn’t unusual. In the mid-19th century, Manchester and Liverpool passed local ordinances aiming to put a stop to court housing, while the 1875 Dwellings Improvement Act gave local councils the power to force public purchases of slums for redevelopment. Leeds, meanwhile, took another course. While it didn’t ban single-aspect homes outright, it did bring in bylaws from 1866 onwards to raise housing standards, make neighborhoods more spacious and improve sanitation. The result was the development of the back-to-backs we know today.