Walk through a traditional machiya townhouse in Kyoto and you will notice something unexpected. The building is narrow — sometimes barely four metres wide — and deep, stretching back from the street like a corridor. The rooms are dim, the walls close. And then, somewhere in the middle of the house, the walls fall away. A pocket of sky appears. Stone, moss, a single tree. Light falls where it should not be possible. A breeze moves through rooms that moments ago felt still.
This is the tsuboniwa (坪庭) — a courtyard garden rarely larger than a few square metres, placed not at the edge of the building but at its heart. The word comes from tsubo, an old unit of area roughly equivalent to 3.3 square metres, and niwa, meaning garden. The tradition dates back over a thousand years, but it became essential during the Edo period when Kyoto’s urban density forced houses to be built wall-to-wall with almost no access to open ground. The tsuboniwa was the answer: a way to bring light, air and nature into the centre of a home that had none.
It was never decorative. It was a device.
A Climate That No Longer Exists
Britain’s period terraces were designed for a mild maritime climate. Deep footprints, small rear windows, thick masonry walls that held warmth through long winters. For the best part of a century, this worked. It no longer does. The UK recorded 40°C for the first time in 2022. Summer 2025 brought four declared heatwaves. 2026 will likely add to that record. Across Europe, heat-related deaths exceeded 60,000 in a single year in 2024. The pattern is not occasional. It is accelerating.
Victorian and Edwardian houses were built to retain warmth. Many now overheat dangerously in summer, with deep rear rooms trapping hot air and narrow side returns blocking cross-ventilation. We have written about the broader challenge of designing for climate change and about passive cooling through natural materials and ventilation. But the most effective response may be the oldest: spatial thinking borrowed from countries that have managed extreme heat for centuries.
What the Courtyard Does
The tsuboniwa works on three levels simultaneously. As a light well, it draws daylight into the centre of a deep house, reaching rooms that rear windows alone cannot serve. We explore the transformative role of natural light as a living presence in the home in our writing on the principle of Hikari, and the courtyard is perhaps its purest application — light arriving not from the perimeter but from within.
As a ventilation shaft, it generates what physicists call the stack effect. The shaded earth and planting at ground level stay cool. Warm air in surrounding rooms rises and is drawn upward through the open courtyard, pulling fresh air in behind it. The result is a gentle, continuous draught that requires no mechanical system, no running cost, no maintenance — only the willingness to leave a small area of the home open to the sky.
And as a view, it does something that no amount of interior decoration can achieve. It gives enclosed rooms a borrowed horizon. Even a courtyard barely a metre and a half wide, planted with a single tree and a ground cover of moss or fern, changes how a room feels. The eye travels beyond the wall. The mind registers depth, weather, the movement of leaves. The Japanese principle of Nagame — the framed view — is at work here, turning a window that might otherwise face a boundary wall into something that calms rather than confines.
Not Alien, Just Forgotten
We recently secured planning permission for a side infill extension with a courtyard to a Victorian terrace in a Conservation Area. The design was met with objections. One response described the courtyard as ‘alien to the area.’
The council disagreed. The approval noted that the courtyard ‘allows for improved light penetration and reduces the perceived sense of enclosure to the adjoining property.’ In other words, even within a formal planning process, the courtyard was recognised as a benefit — not an oddity.
The courtyard itself is modest — approximately 2.5 metres deep and 1.6 metres wide. It sits where a conventional side return extension would typically begin, but instead of filling the entire length with built form, the building pauses. The extension starts after the courtyard, roughly two and a half metres beyond the original rear wall. Three openings look into it: an access door from the second reception room, the bathroom window directly beside it, and a picture window from the new dining area. Every room that faces the courtyard gains light, ventilation and a view that would not otherwise exist.
There is a quiet irony in calling this approach alien. London’s own architectural history has its own vocabulary for letting light and air into dense terraces — the front area, the rear court, the basement lightwell. These were not courtyards in the Japanese sense, but they recognised the same need: that a deep, enclosed house must breathe somewhere. Many have since been filled in or built over. The tsuboniwa draws on a tradition that never stopped refining the idea.
The Willingness to Leave Space
The courtyard requires no technology. It asks only for a decision that many homeowners find counterintuitive: to leave a pocket of the footprint unbuilt. In a city where every square metre carries a price, the instinct is to fill. Extend to the boundary. Maximise floor area. Use every inch.
But a home is not measured only in square metres. A courtyard of four square metres that gives three rooms light, air and a connection between inside and out is worth more to the quality of daily life than the same four square metres enclosed under a roof. The value is not in the space you gain. It is in what the space you leave open gives to everything around it.
Period houses can adapt. They were built with good bones — solid masonry, generous ceiling heights, layouts that respond well to careful intervention. But adapting them for the climate we actually face, rather than the one their builders imagined, requires a willingness to think differently about what an extension means. Sometimes the most intelligent addition to a home is a small piece of sky.