Architecture: Some concrete proof of changing tastes: The listing of a once-reviled Seventies estate marks a profound shift in attitudes to post-war buildings, writes Dan Cruickshank

THE DECISION last week to add the Alexandra Road public housing scheme in Camden, north London, to the nation's list of buildings of historical or architectural interest highlights the growing fascination with post-war architecture in Britain.

Not only is the housing scheme, designed in the Sixties but completed in 1976, Britain's youngest 'historic' building, its elevation marks an extraordinary change in taste.

Soon after its completion, Alexandra Road became synonymous with much that was perceived to be wrong with modern architecture in Britain. The ruthless repetition of the housing units and stark geometry of the composition was taken to represent the triumph of the architect's preoccupations over tenants' needs and aspirations.

This position is now transformed. After a few years in the doldrums, Alexandra Road is enjoying real popularity with modish historians and its tenants, who have discovered that living in an environment made by a thoughtful designer can be a surprisingly pleasant experience.

In recent months, tenants have even opposed alterations proposed by Camden planners as a means of making Alexandra Road more occupier- friendly. The speed of change in popular taste caught the council by surprise. Neave Brown, who designed the Alexandra Road scheme and spent some years in a professional wilderness after its hostile reception, is equally surprised.

'This is wonderful,' says Mr Brown, 'a statement of the rare valuing of cultural and social achievements in the face of our almost institutionalised British process of neglect and degradation.'

English Heritage historians - the people responsible for recommending buildings for listing - have seen through the haze of contention that inevitably surrounds contemporary architecture of pronounced character and have protected one of the most distinctive buildings of its type and epoch from unsympathetic alteration or well-meaning mutilation.

In the Sixties, Victorian architecture was the popular discovery; in the Seventies, Georgian enjoyed a revival, and in the Eighties, the thrills of inter-war architecture were discovered by the discerning enthusiast. Now the obsession is for post-war architecture, and the more obscure and uncompromising it is, the better.

Gavin Stamp, pioneering campaigner for Victorian architecture, unofficial historian of the Georgian Group and founder committee member of the Thirties Society, is now chairman of the Twentieth Century Society. His talks on the more outre aspects of post-war European architecture have become popular with a new generation of architectural enthusiasts.

To many, the products of the inter- war and post-war periods are untapped territory, rich with novelty value as well as being deliciously risque. To admit to a passion for early Denys Lasdun or late Basil Spence still has the power to shock dinner- party guests.

But how is the best of recent architecture to be identified, and how is it to be protected? Conservation legislation was framed to protect ancient buildings whose qualities could be recognised with relative ease, not concrete houses.

Should a single house from a pioneering estate such as Alexandra Road be listed? This would be absurd when it is the combination and composition of Neave Brown's flats that makes the design significant. Should avowedly functional buildings be preserved when they cease to have a function? Logically, a truly functional building should be eliminated without emotion - in the same way as an outmoded car - when it loses that function.

If the best modern buildings are essentially functional and, therefore, potentially ephemeral, is the idea of listing them at odds with the nature of conservation laws that might seek to preserve them? This debate has been aired recently when two important and functional buildings - in Ipswich and London - have been faced with alterations reflecting the functional requirements of their owners.

The new owner of the mid-Thirties house designed by Eric Mendelsohn and Serge Chermayeff in Old Church Street, Chelsea, has proposed interior alterations that would change the elevations of the listed house. This outward expression of slightly revised functional requirements ought to pose no significant problems for a Modernist house, especially as Sir Norman Foster has designed the alterations.

Yet the scheme has become a cause celebre among the self-appointed guardians of 20th-century architectural heritage. Many emotive articles have appeared, including one in the current edition of Docomomo (the journal for those seriously committed to the 'documentation and conservation of Modern movement architecture in Europe'), which claims that the proposed alterations would 'radically upset the composition . . . undermine the cubical massing of the building . . . and neutralise the tension of the rear elevation'.

Foster has himself been the victim of comparable proposals, when his glass-fronted Willis Faber office building in Ipswich, completed in 1974, was threatened with internal alterations thought necessary by the owners. Professional and public outrage followed the submission of a seemingly innocuous planning application, the hapless occupiers being confronted with the sort of anger usually focused on those attempting to despoil ancient buildings. The consequence was a speedy spot-listing by the Department of the Environment, making the office the then-youngest listed building in England.

The passionate defence of these buildings makes it clear that even architecture that appears to make a fetish out of functionalism and rational design can acquire cultural importance and sentimental appeal way beyond the conceptions of those who commissioned and designed it. But when does a building stop being just a building and become part of our heritage? English Heritage is now trying to develop a rational, objective method of listing post-war buildings.

Its rule of thumb is that buildings less than 30 years old should be listed only in exceptional circumstances, and that buildings less than 10 years old should never be listed. But these criteria have not been enshrined in legislation and are generally seen as a rather crude means of judging a building's architectural significance.

The current policy is to undertake comparative studies of various post- war building types in order to produce a well-balanced schedule of recommendations for listing. Post-war architecture in Britain is characterised by the pursuit of great social concerns. So the first study, last year, focused on schools and resulted in almost 100 buildings being added to the statutory list. The latest study is examining industrial and commercial buildings.

About 140 post-war buildings are currently listed. One of the bravest examples is the massive, handsome Brynmawr rubber factory in South Wales, which was completed in 1951 to the designs of the Architects Co-Partnership and listed in 1986 after standing redundant for six years. No new use has been forthcoming.

Might this type of building be eligible for acquisition by the National Trust? The trust has already reflected the new taste for Modernism by campaigning to acquire the late Thirties Hampstead home of Erno Goldfinger, one of the most significant Modernist architects to work in England before and immediately after the war. It is has also expressed interest in a similar house. Since the trust is clearly interested in protecting some of the best examples of England's modern architectural heritage, might it consider taking buildings other than private houses? Should it acquire a factory, school or housing estate?

This may not be as absurd as it sounds, for the trust already owns and manages a smattering of commercial properties, including shops and pubs in London and Belfast. If the trust were to take on the protection of a Sixties estate, and raise an endowment to maintain it, then we would know that Modernism has come out of the cold and become as much a part of our popular and national heritage as the half- timbered house and Georgian terrace.

The author is editor of a new architecture magazine that will be published in conjunction with the Prince of Wales's Institute of Architecture.

(Photograph omitted)