The Lakeside Studio is part of a large single-storey house located in an exclusive suburb in Sacramento on the north bank of the American river. Designed for a wealthy developer and his wife, and intended as a place for work, relaxation and the display of part of a large art collection, the new studio is an extension of the original house as well as a self-contained environment.

British-born architect Mark Dziewulski trained under Sandy Wilson at Cambridge, graduating in 1982. He then went to the US on a Fulbright scholarship and earned his Master of Architecture degree at Princeton. After several years' apprenticeship with east-coast firms, including SOM in New York and Michael Graves in Princeton, he moved west to California and set up a practice in the California state capital, Sacramento. For the last seven years he has been working on a variety of projects, including urban design and retail stores for companies such as Virgin Megastores in the shopping centres that dot the sprawling suburban landscape there. The Lakeside Studio establishes a new direction and represents a turning point in his career. Dziewulski is about to open a London office to work on some residential apartment projects there as well as on a National War Memorial in Warsaw, Poland.

Sacramento is a Central Valley city, about 130km inland from San Francisco, with a growing population of nearly half a million people. Despite being the governmental centre of the world's sixth largest economy, the place can seem extraordinarily provincial. The city centre is a grid-iron town plan dominated by the domed State Capitol Building and the more recent high-rise towers of the adjacent business district. Most of Sacramento is suburban in character, a freeway-oriented sprawl of tract homes, business parks and shopping centres stretching east and south along the banks of the Sacramento and American rivers. The most exclusive neighbourhoods are located to the east, laid out under a canopy of Californian live-oak and elm trees that provide shade from hot, dry summers.

The original Lakeside house was built in the 1960s. It is a single-storey residence with a low-pitched roof and a large central atrium space protected from the winter weather by a retractable glazed roof. The atrium,

landscaped as a tropical garden, contains a large fish pond filled with multi-coloured carp and is the central focal point of the house. Despite being situated on the bank of the broad and fast-flowing American river, the existing house provides few views of the water. The low, overhanging eaves made the house seem quite dark, especially on bright, sunny days.

The clients purchased the adjacent lot with the intention of creating their own lake as a setting for a new extension to their home. They commissioned Dziewulski to design a studio/living room that would also act as an office and be a setting for entertainment and the display of a widely diverse collection of art. The clients are active in both state and national political circles and wanted a place for fundraisers with large numbers of guests.

Early designs explored the idea of adding to the house in the woodsy manner of the original. These were soon rejected in favour of a more contemporary design that broke away from both the materials and the geometry of the existing structure.

The built design departs radically from the original house and yet is quite compatible with the spirit of the older context. The 120m2 room is shaped like a scimitar, curving in plan and section, reaching out to both the view and the light. The two side walls are not parallel, but curve out in the form of a spiral whose centre is at the pool in the atrium space of the existing house. The new studio projects out over the lake with the full-height mullionless windows that stretch the limits of glazing technology. The experience is of floating out over the water, a feeling that is reinforced by the use, in one location, of a glazed floor panel that permits you to look down at the water below.

The ceiling and roof forms slope gently upwards towards the sky, terminating in an extensive overhanging plane. In contrast with the existing house, whose overhanging eaves keep both light and winter rains out, this overhang is intended to protect not only from direct southern exposure but also to permit reflected light from the water below to flood into the interior space. As a consequence the studio is extraordinarily light and open. A line of circular, translucent skylights permits both daylight and artificial light to pour into the interior. The ceiling planes are detached from the side walls where they occur in the back of the studio so that the effect is of disconnected surfaces sliding past each other like a Suprematist painting. A minor criticism is that the circular skylights are all the same size, whereas it would have appeared more logical if they had increased in size, thereby reinforcing the idea of the spiral plan that grows from its centre.

The side walls contrast with each other as they emerge from the existing house. The western wall consists of a thick storage element containing shelves and cupboards that are interspersed with windows and mirrors. The use of these elements is similar to the sophisticated games that Le Corbusier would play in his early Cubist houses in Paris, where the exact location of inside and outside planes was deliberately ambiguous. The eastern wall that opens out to the river view, but also looks back to the existing house, is made of a zig-zag pattern of translucent and transparent panels that focus the view away from the house and maintain the privacy of an adjacent bath room. The translucent panels are also an ideal illuminated backdrop to the various works of sculpture on display.

A glass door to the side of the room opens out to an elegant stainless-steel staircase cantilevered over the lake. This leads down to the garden to a meandering path around the edge of the lake and further to the river's edge. From across the lake you can see the articulation of the structure and how the cantilevered floor and roof plane are framed within a large portal, made up of green limestone-clad verticals and supporting a curving steel beam above. When the lake is still, the effect is of a mirror, doubling the size of the cantilevered room. When the water ripples, either from the wind or the underwater supply jet, it causes a constantly changing pattern of dappled light to reflect on the ceiling. The large circular oculus that terminates the line of skylights within the studio permits a shaft of sunlight to mark the passage of time as it moves across the floor and walls.

At night, the elaborate interior lighting causes the studio to glow when seen from outside and to celebrate the daring cantilever over the water. Lighting can be adjusted to create a variety of conditions and moods. For example, the sole source can be from the circular skylights or alternatively from the display walls on either side. On other occasions, interior lighting can be reduced to a faint glow so that the primary source is from the floodlit sculptures across the lake.