How to make a building fit its surroundings: Japanese architect Kazuyo Sejima offers some examples

In a Wuzhen lecture titled Environment and Architecture, she set out her core idea: tearing down the traditional architectural boundary between indoors and out.

For the Wuzhen art exhibition, Japanese architect Kazuyo Sejima brought an outdoor installation called Another Water Surface. Sixty stools of mirrored stainless steel, set in four concentric rings, form a circle that catches the sunlight and takes on the shape of rippling water. Each stool is itself shaped like a ripple, its rim slightly raised.

Sejima is an architect, not an artist, and she said so in Wuzhen: "We probably understand a site more from the point of view of a city's public life. So I wanted to make something people could actually use." Another Water Surface thus became the only piece in the whole exhibition that also had a use. On a site that rises and falls, the daylight bouncing off the stools pulls people into the space and invites tired visitors to sit down.

This is the question Sejima has kept returning to: how to make a building merge with its surroundings and still be public — usable by more people. SANAA, the firm she founded with Ryue Nishizawa, won the 2010 Pritzker Prize; the jury's citation said they "create buildings, based on the task at hand and the available budget, that are unpretentious and democratic." That democratic quality shows up in her designs for public art spaces, the best known being the 21st Century Museum of Contemporary Art in Kanazawa and the New Museum of Contemporary Art in New York.

Unlike the traditional boxy layout, the Kanazawa museum is a circle. The white galleries of a conventional museum were broken into smaller cubes and scattered across a circular base. The outer wall of that base is all glass, erasing the line between inside and outside. The museum has no main entrance; visitors can walk in from any point on the circle.

In a space that open and that clear, SANAA dismantled the authority museums used to carry and turned the building into somewhere ordinary residents could wander into after dinner. The design also won the Golden Lion at the 2004 Venice Architecture Biennale. In its first year the museum drew 1.57 million visits, in a city of fewer than 500,000 people.

For the New Museum of Contemporary Art in New York, SANAA stacked six white boxes off-centre, so the building as a whole reads as a half-transparent space. The windows sit on the outer edge of each box, and every box has a different floor area and height, to suit different kinds of contemporary-art display.

One of SANAA's first goals here was a museum that felt approachable and inviting. The street-level floor is walled in glass, a statement of openness. And to match the rough character of the Bowery, where the museum stands, the exterior is wrapped in two layers of industrial aluminium mesh, which softens the building's edges, makes it more transparent, and settles it into its surroundings.

On April 3, Sejima gave a lecture in Wuzhen titled Environment and Architecture. She opened by stating the core idea behind her designs: she wants to break down the traditional architectural boundary between indoors and out. Every one of her projects rests on that idea, worked out through a different strategy each time.

Sejima finished her master's degree at Japan Women's University in 1981 and joined the office of the Japanese architect Toyo Ito. She set up her own practice in 1987, then founded SANAA with Ryue Nishizawa in 1995. When the two won the Pritzker in 2010, Sejima was only the second woman to receive it and Nishizawa the youngest laureate ever. SANAA's buildings are light and transparent and use a great deal of white; the thinking behind them stresses the fusion of a building with people and with what surrounds it.

She began her case studies with the Rolex Learning Center at the École Polytechnique Fédérale de Lausanne (EPFL), finished in 2010. She considers it a landmark for SANAA: from this project onward you can trace the different directions the firm's work has taken.

The combined student centre is a single continuous 20,000-square-metre open floor. The building is a rectangular block touching the ground at its four corners, with a floor that rises and dips and links 13 courtyards of different sizes and shapes. Its most striking feature is that no vertical interior walls divide it — all the inside space runs together. The undulating floor does the dividing instead, a "soft partition" between areas. The rises and dips give pedestrians outside routes across the site and give the building several entrances. The low points serve as entrances to the Learning Center, while the high points look out over Lake Geneva. Some of the interior slopes reach 30 degrees.

Nishizawa once said: "Without walls dividing it up, any activity can happen anywhere. It's more like a park." EPFL president Patrick Aebischer saw it as boundaries coming down: "This new campus centre reflects our vision for the university, breaking down the boundaries between traditional departments."

But Sejima told the audience that because the building's rectangular edge is still so pronounced, the Learning Center fell short of the ideal relationship between a building and a city. After it, SANAA began trying to get away from clearly geometric architectural space, hoping to dissolve the sense of a boundary with neighbouring buildings not only physically but at the level of a city's culture and history.

"Dissolve" was the word Sejima used most often in that April 3 lecture. She wants to dissolve a building's bulk so that it sits easily with what is around it, as naturally as possible.

The Louvre-Lens, which opened in December 2012, is one such exercise. This museum runs 360 metres long and covers about 28,000 square metres, and holds works from 3500 BC to the mid-19th century; the first design move was to split it into four rectangular volumes and one large square hall.

It stands on a disused mine site in Lens, in northern France. The place was once the largest coal heap in Europe; since the mine closed in 1960 nature has slowly filled it back in, though the ground still swells slightly where the pit was overfilled. SANAA built to follow that terrain. Inside, the floor follows the original slope: on first walking in you can see the whole exhibition space, but as the ground drops away and you move among the works, you see them only a section at a time. The interior also drops the traditional habit of displaying works by category — there is not a single dividing wall, so every piece stands directly in front of the public.

The building's skin is glass and aluminium. The polished aluminium panels of the façade refract natural light and scatter it, so the long building merges with the park around it. The glass curtain wall lets sunlight fall inside, and a hidden roller-shading system in the arched roof kicks in when the light gets too strong, protecting the works on show.

SANAA wanted a museum held by nature, highly permeable, and still carrying traces of the mine. In plan, the façade is in fact a faintly curved line; Sejima said she wanted the curve to dissolve the strong geometric mass and strike a harmonious relationship with the natural state of the abandoned industrial site.

The expansion of the Art Gallery of New South Wales in Sydney, now at the construction-drawing stage, is a staggered building that merges with nature. It has seven pavilions, added on top of an uneven existing site and a set of Second World War oil tanks; the tanks themselves are kept as exhibition space.

Each pavilion sits at a different level of the site and faces a different way. The roofs at those different levels double as parkland, letting people look at the city from different angles.

It will be the first public art museum in Australia to meet the highest environmental standards. Along with designing the exhibition spaces, the project opens up the surrounding landscape for public use — the outdoor public art garden stays open around the clock — and keeps the green character of Sydney's cultural district. The design also saves two fig trees more than 100 years old near the building's northeast corner.

For the Nishinoyama collective housing project in Kyoto, the local government required one unified hipped roof over ten households. To dissolve that big mass, SANAA cut the roof into 10 units: three roof panels per household, with half of one of the three shared with a neighbour. The design keeps each home's interior private while still giving residents the feeling of living together, holding on to the bonds that come with shared living. And once cut apart, the roof sits far more easily among Kyoto's narrow streets.

Sejima has no finished project in China yet. A few years ago she and Nishizawa designed the Huaxin Financial Center on Shanghai's West Bund, and over the past year or two she has taken on several public buildings in China. In the question session after the lecture she said that in Japan today it is hard to think about, and act on, what a building does to a city and to a society. She thinks China may allow a richer, more layered way of thinking about architecture — but nothing has been completed yet, and she is still working it out.

Cover image: the Rolex Learning Center at the École Polytechnique Fédérale de Lausanne, from the EPFL official site.