A new house on the Thames in London not only accommodates a family of 10, but offers special flood-prevention measures and a clever scheme for taking in natural light while maintaining privacy. It’s called the Garden House, as it sits in a sunken garden courtyard surrounded by open terrace and greenery. But its real achievements are harder to guess. The sculptural volumes contain a five-bedroom house; the glamorous-looking courtyard is actually a high-sided watertight concrete container, and the blank upper walls conceal light wells that cleverly let in sunlight without overlooking the neighbors.

When a new marriage created a family with seven children, architects De Matos Ryan were called in to add an extension to a house near the Thames in London. However, the requirements changed when another child was on the way and the idea of replacing the old garden shed with rooms for the older children was re-examined. It was decided that the new, larger building would house the parents and younger children.

But to fit the necessary rooms, the house needed two stories. As most of the neighboring properties are single-story, this meant the new house would have to be partly below ground. So a scheme was devised to lower the garden, bringing the house down a level and creating a private, enclosed outdoor space.

A swimming pool in reverse

Unlike many of the new and increasingly elaborate basement conversions being created all over London at the moment, this was only a single-level excavation. Still, being on low-lying land, it had to meet new regulations with regard to flood protection. So the architects created what they call "a swimming pool in reverse," by tanking the excavated area with a waterproof membrane and concrete. This protection runs up above the floor of the garden courtyard, providing a dry well, if you like, into which the house was sited, leaving space for the paved terrace and garden area, which includes a path from the old house.

Light without overlooking

The house in its sunken white setting looks like a stylish modernist cube, with a solid white concrete volume perched lightly over the glass-walled ground floor. Open-plan spaces on the ground floor connect with the new level courtyard area, creating a large open terrace space that also links with the old Victorian house, now the domain of the teenage children.

The glass walls are full height with an "open" corner that is free of supports, so that when the doors slide open, the upper volume appears to float over the living space. The floating theme was continued inside, where the dining table cantilevers from the kitchen worktop. At this level, the glazed areas are only on view within the private garden terrace.

Bedrooms are on the upper floor, with windows located on the rear and side elevations. The blank walls on one side were the answer to another constraint of the design, which was that any window openings not directly overlook the neighbors. This is tricky on an upper floor located on a dense site. The architects compensated by using internal light wells and roof lights to bring in natural light from above.

The light wells were created by extending the envelope of the walls beyond the lower floor structure, leaving a gap between the wall and the structural frame. The gap is covered in glass and concealed from view from the outside by the overhanging walls. On the inside, however, light comes in from above and below, and the residents have a view of the sky and the courtyard,

Forward-looking design

Overall the Garden House presents a cool, modern, sculptural form, but its low profile means that it doesn’t deliberately jar with any of the neighboring models. The fact that this house had to conform to flood prevention regulations even though it is not in an area known to flood easily demonstrates that flood risk is something architects will need to contend with more often in future, and in new ways.

The innovative use of roof lights and light wells to address issues of privacy and natural light is another forward-looking facet of this project. As density continues to increase in urban environments, the challenge will be for everyone to have their share of natural light without sacrificing privacy to get it. With this house, De Matos and Ryan have provided an elegant solution on both counts.

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