Attached or detached: townhouses and density

One of the big differences that is immediately obvious to anyone visiting Japan is the almost total absence of what is a clear favorite of European and American planners and urbanists: the townhouse. This form of high-density family housing where houses' lateral exterior walls are joined is clearly beloved by a lot of them.

Random street in London, the UK is particularly fond of townhouses that they called "terraced house", nearly 70% of the population lives in attached homes

The presence of these buildings built wall-to-wall is common to almost all European cities, it is typical of European classical urbanism.

Even though the Japanese have plenty of high-density areas full of single-family houses, these areas almost always steer clear from townouses. They do have a few of them, mostly in older areas, and some developers build apartments in townhouse format rather than in the typical format.

Apartment building built in a townhouse format in Sendai

But in most cases, the Japanese avoid shared walls at almost any cost, even in areas where it would seem to make a lot of sense:

This is an image from Osaka

These houses have been built at the same time, probably by the same developer (traditionally, the Japanese built their own homes, but in recent years, developers have taken to building entire neighborhoods of single-family houses and selling them), yet despite their proximity, they are not attached, with the smallest of space between each of their exterior walls.

The basic logic of the townhouse

There is a simple logic behind townhouses and attached buildings in urban areas. The biggest attraction point of single-family housing over multi-family is the promise of one's own personal yards, access to a small portion of land that is shared with no one. The back yard is the single most important selling point of single-family housing. The front yard is still important in preserving privacy and offering a customizable façade for the house, so that's another big selling point.

If we look at a single-family house schema, we'd get this:

Basic schematic representation of a single-family house

Now, considering in general the depth of the plot is imposed by the street network and that there is only one household on that plot of land (let's ignore accessory units here), then the only way to achieve higher densities is to play with width, to make the plot narrower.

A typical house tends to be wide but shallow, a way to increase density is thus to rotate it, so the shorter side is facing the street.

This achieves nearly twice the density of the house above

But people can look at this and say: "The back yard has value to the owner, the front yard also... but what about the pieces of land on the side of the building? They are too narrow and small to be of any use, they're not really visible from the street and they don't really help much for privacy". So a seemingly obvious solution is to simply get rid of them, just build homes wall-to-wall.

For urbanists focused on "feeling" or on the look of areas, the presence of buildings wall-to-wall reinforce a feeling of enclosure, of unbroken lines of buildings forming walls for the street, which they frequently seek as it evokes European cities.

The problem with townhouses

Townhouses seem to make a lot of sense, but they have one big flaw: the lack of exterior walls on which windows can be installed.

It is a factor that may be often forgotten, but windows are crucial for proper living quarters. It's not just about the view, but about air flow and natural illumination. In some jurisdictions, it is downright illegal to have a bedroom without a window to the outside, and even when it is legal, people avoid them like the plague, with good reason. Even a window opening on a wall within a few feet of it is considered much more desirable than no window at all.

Of course, in the past, before efficient house heating, building houses side-to-side reduced heat loss in winter and made it easier to keep living areas warm. However, today we no longer have problems with heating, so that advantage is much less significant than in the past.

If you look at the picture of the Japanese homes, you can notice windows on the side walls, even with the tiny amount of space available. I also have seen such windows in Tokyo Hotels, for example:

Photo from the inside of a Tokyo hotel room

With the window opened

A picture taken right out of the window, showing what space there is between the two walls

So, visually let's compare a small detached house with a townhouse of the same size:

The blue bars indicate where windows can be installed, the red bars show where they can't

In this case, supposing a 7m x 7m (23ft x 23 feet) detached house with a 5m x 10m (17 ft x 33 ft) townhouse, the detached house has 28 linear meters of walls per story that can be equipped with windows, of which 14 meters are the front and back, with better air flow and light. The townhouse on the other hand has only 10 linear meters of walls per story that can be equipped with windows.

This also means that the detached house can have more bedrooms for a same floor area as bedrooms need to be located next to an exterior wall with windows.

There is a major difference between Japan and North America that may explain partly why the Japanese favor small detached homes over townhouses. In North America, parallel streets are often separated by 60 meters (200 ft) or more, as a result, lots tend to be very deep. In that context, reducing width is essential to get some density. Meanwhile, Japanese streets are built much more tightly together, separated only by 35 or 40 meters (120 to 130 feet), so the Japanese don't need to build narrow townhouses to get high density in single-family areas, the lots can be wider because they are a lot shallower:

Left: townhouses in a typical North American street grid, right: small detached homes in a Japanese street grid, both images have the same density

Left: a random neighborhood of Minneapolis, right: a recent random single-family area in the small city of Sano in Japan, yes, the images are to scale

This is true for townhouses, but also for apartments. Apartments built in depth with little frontage will also struggle to find ways to have many bedrooms because of the lack of windows. This is why Montréal, which housing stock is primarily made up of low-rise apartment buildings built side-to-side, struggles to have more than 2 bedrooms per unit in that type of housing, as it is very hard to design an apartment that has three bedrooms with a townhouse-style floor space with windows only on the narrow front and back.

In the past, people have found a way to go around this problem by using a fat, reversed L- or T- shape.

Apartments with a T-shape in Montréal, separating the walls in the back of the buildings to create more exterior walls and opportunities for windows

Another example in Montréal, more of an reversed L-shape here

Now an American example, Philadelphia, with its traditional rowhouses with L-shapes

The result of this effect is that it is a very clashing experience to live in a detached home and in a townhouse. The lack of windows on the townhouse can be downright claustrophobic for one used to living in a detached house, like the younger generation is.

A compromise: the semi-detached

The semi-detached is a compromise between the attached buildings and detached buildings. With just one shared wall, the semi-detached can still have plenty of windows while reducing the lateral buffers between buildings. This can provide for greater density while maintaining some of the attraction of detached houses, it can also provide a way to deal with the deep North American lots by allowing for the construction of very deep houses or apartments, increasing building coverage to the lot that would hardly be possible in an attached context, and increasing the possibility of building more bedrooms per unit.

Semi-detached houses in the UK, where the style is quite common in more suburban areas

Semi-detached houses in Boucherville, double the density of typical bungalows, but each unit is still wide enough that it doesn't necessarily require side windows

A multi-family type of semi-detached, each floor has two units built in depth with windows mostly on the side of the building, as a result on a 30m-deep lot (100-ft), the buildings are 15-m deep (50-ft) and the apartments manage to be just 5m-wide (17-feet) yet have 2 bedrooms each, which would be impossible in an "attached" situation without making one bedroom just 2m-wide or less (around 6 feet)

Typical condos found around Montréal, which are basically two semi-detached triplexes built in one building, providing big (1000+ square feet), affordable housing options in suburbs

Conclusion

If attached buildings and townhouses represent a very efficient spatial organization and are typically associated with urban areas, especially in Europe, they are not necessarily required for density and good urbanism. Though they are also well adapted to the typical deep North American lot, townhouses' lesser access to air and light may be a turn off for a generation born in suburbia who may crave more density but who still remains attached to a detached lifestyle (pun not intended). This may also explain why I personally find residential areas in Japanese cities more attractive than European cities, due to better aeration and light access, as I was raised in a North American suburb and am more used to the more open, less enclosed feel of them.

Oh, and finally, a last point about why the Japanese skirt around attached buildings: remember that the Japanese think that buildings have a limited life expectancy, that they should be torn down and replaced every few decades, whereas the European/North American approach is to consider buildings to be built to last at least a few lifetimes. The Japanese approach of tearing down and rebuilding is much easier to do with detached buildings than with attached buildings where tearing down a building without affecting the ones on either side with which it shares walls and which belong to different owners can require a lot of attention and care.