Summer house.

In the post-war period, Norwegian architecture was polarised between two schools. The group led by Arne Korsmo were committed international modernists. The other group, led by Knut Knutsen, were much more regional. Without ignoring Modernism, particularly the organic stream, they learned from traditional Norwegian country buildings. Knutsen's cottage near Portor, was his most earthy and organic work and acquired talismanic significance.

Knut Knutsen's summer house near Portor on the east coast of southern Norway is nearly invisible. It hides behind rocky outcrops and pine trees and has a topological form which, chameleon-like, melts into its surroundings. It is located in an area inaccessible by road and is not easy to discover. In fact, not many people have seen Knut Knutsen's summer house. None the less, this modest building looms tall in Norwegian architecture. The State Official for Conservation has awarded it monument status and it occupies a central position in the consciousness of Norwegian architects. Why?

I arrive there for the first time one gleaming summer morning. The car is parked by the road. Knut Knutsen's son, the architect Bengt Espen Knutsen, leads the way along the barely visible track over the gently undulating landscape out towards Kragero Fjord. We startle a nesting eider-duck. The bird won't often be bothered by such disturbance, for the houses here are few and far between Knut Knutsen bought 3.5 hectares in the first post-war years when the prices were at a very different level. In the direction of Portor we see Harald Grieg's summer house (1937) designed by Arnstein Arneberg. Another few houses have been added in recent years, but you still get that sense of being alone with the sea and the wind.

Knutsen's house, now to the left in front of us, resembles his familiar sketch of it, but some things are different: the bedroom wing is broader. And the white-painted ceilings are a surprise. And I did not know about his wife Hjordis' decorations. She has also contributed the woven rugs in the living room and the curtains, originally designed for the Viking Hotel in Oslo. It strikes me as appropriate and important that they should both have made their mark on this summer home.

The bedrooms are small cabins off an open loggia. The doors are split and you understand that the summer evenings have been warm here, and infinitely long, and the upper part of the door was left open to let in a mild breeze. Here it is possible to experience, to live, in unity with the natural elements. And here, one summer evening in 1969, Knut Knutsen quietly drew his last breath.

In the big Knut Knutsen monograph which was published a few years ago, the authors suggest that the Portor house represents the culmination of Knutsen's career. The house is shown on the dust-jacket, embossed on the cover and generously presented in the book itself. This presentation includes some magnificent colour photographs, but otherwise architects have been fed a starvation diet of old, woolly black-and-white pictures taken just after the house was finished.

As a result, it is not the pictures which have transmitted the importance of the Knutsen house and given it such a predominant position. It is more likely to be that little ink drawing, Knutsen's rough perspective sketch, an icon carved on the brains of Norwegian architects. And it seems appropriate that this house, itself barely visible, hardly existent, lives on mainly as an idea conveyed by an architectonic hieroglyph.

But where does the idea come from? In the monograph the authors write: 'If one must search for his sources of inspiration, these will most likely be Eastern architecture, and also his great idol, the American architect Frank Lloyd Wright'. Such an appraisal may well prove very useful. But let us begin with an attempt to place the Portor house in its own time and try to see its relationship with contemporary buff clings.

When Le Corbusier's pilgrimage chapel in Ronchamp was finished in 1955, it was received with astonishment. The chapel was denounced as theatrical and irrational. It was worrying that the old master had created an expressionist building rich in metaphors. As Mies van der Rohe's cool, refined boxes were copied across the globe, suddenly an alternative had been launched. Two years later Jorn Utzon followed suit with his remarkable competition project for the Sydney Opera House, and in 1961 the TWA terminal in New York by Eero Saarinen was opened. Simultaneously with these expressionist tendencies, Reima Pietila was developing further Alvar Aalto's dialogue with nature. Pietila's Dipoli student centre was finished in 1966, and in 1963 he designed a competition entry for the Finnish embassy in New Delhi, where he lets the roofs wave so they resemble geological forms. The year 1963 also saw the Berlin Philharmonic opened, important because its architect, Hans Scharoun, represented a connection back to the German expressionism of the inter-war years. We do not know how much Knut Knutsen knew about Bruno Taut's 'Alpine Architecture' (1918), where crystalline building forms seemingly grow out of the mountain. Or whether he had seen Wassili Luckhardt's 'House for an architect' (1920), a house which bears a striking resemblance to Knutsen's own summer house.

But whether Knutsen was aware of German expressionism or not, the Portor house can be regarded as part of the new wave of anti-rational tendencies flooding international architecture in the years following the Second World War. And, more interestingly in the international context, Knutsen is a pioneer in this revolt against rectilinearity.

The first part of the Portor house was finished in 1949, six years before the chapel at Ronchamp was consecrated. It is natural to see a parallel development in the two buildings, or to put it differently: the Portor house is the Norwegian Ronchamp. Both represent a revolt against the simplified and unemotional version of functionalism. Both are the beginnings and points of reference of the development which followed. Where Le Corbusier could gather inspiration from his work as a painter and a sculptor, Knutsen expressed an empathy with the landscape, taking the opposite course from the Swiss. Knutsen the Norwegian submits to the landscape, giving nature a pre-eminence which anticipates the ecological attitudes today.

Many Norwegian architects have been affected by Knutsen's summer house, but we shall limit ourselves to tracing a few of the lines. At the end of the 1970s a radical architectural movement started to develop in Bergen, drawing on unorthodox disciplines (like meteorology) and simultaneously looking for other formal impulses than a petrified modernism. For this movement, consisting of CUBUS (p34), Svein Hatloy, Bjorn Simonnaes and Arbeidsgruppen HUS (p50), Knutsen's summer house (and anthroposophical impulses) became an important source. This is particularly noticeable in the freely formed roofs. Tveiteras school (1974) and Loddefjord School (1975) consist of long building volumes which adapt to and reflect the irregularities of the landscape. Both these CUBUS-schools have connected roof-planes which undulate like landscape forms. Brekkestranda Hotel (project 1966, finished 1970) by Bjorn Simonnaes is an even more obvious part of the Knutsen tradition. Certain sections of the building bear a formal resemblance to the Portor house, but Brekkestranda has a turf-covered roof and a roughness which Simonnaes does not get from Knutsen. During the material shortages following the war, Knutsen used old shuttering boards for the outer cladding. Inside he painted the interiors white. There is something unpretentious and refined about the Portor house, while Brekkestranda is as rough-hewn as the Hall of the Mountain King. This does not, however, prevent the hotel at the outermost end of the Sognefjord from being a very personal piece of work and an unmissable part of our recent architectural history.

It is tempting to extend the lines from Portor to Brekkestranda and further into the Atlantic, to the Faeroe Islands. When Ola Steen won the architectural competition for the Nordic House on the Faeroe Islands (AR July 1986, p67), he presented a somewhat schematic proposal which none the less had a clever and flexible plan. The building which opened in 1983 had acquired an elegant interior and a turf-covered roof which turns the house into another formation in the landscape. The Nordic House is one of the most important buildings designed by a Norwegian architect in the last decade, and as such it is perhaps not so strange that one should notice the echo from Torshavn on the Faeroe Islands all the way to Rogaland in Norway where Sola Cultural Centre was built at the end of the 1980s.

Even more obvious is the connection from Knut Knutsen to Per Line, Knutsen's last assistant. At the end of his life Knutsen designed Thorkelsen's summer house (1961), situated about one kilometre south of the Knutsen house and a further development of that first building. It is particularly Thorkelsen's summer house which has been the basis for a series of single-family houses and holiday homes designed by Per Line at Jaeren on the west coast of Norway (AR September 1990, p87). The Open-air house at Orre (1987) is the largest and most ambitious of these buildings. Both of the summer houses Knut Knutsen designed outside Portor consist of two parts: a living house and a bedroom wing, and between them a covered terrace with a wall of windows on one side.

Thorkelsen's house is on a more exposed site than the Knutsen house, so it closes itself off with a U-shaped plan around a courtyard. The plan is more geometrically arranged and the roof is one single inclined plane. Thorkelsen's house is more obviously modernist, while the Knutsen house is more striking, as a picture. And it is as a picture that the Knutsen house will continue to live with us, a picture of the Norwegians' yearning for unity with nature.