If ruins and ghost stories aren’t for you, there are more positive tales to tell. As fashion and culture have changed over the past two decades, many brutalist buildings have found themselves unexpectedly protected, preserved and renovated. Some that were destined for the scrapheap are now listed and treasured, forcing the narrative around them to change. In the UK at least, once listed, local authorities or private developers can’t just move in on buildings for an easy kill. Instead, celebrating them has become a duty, or at least a necessity bestowed by official protection. And in some cases this has led to a resurrection for buildings that had fallen into disrepair.

Preston Bus Station, in Lancashire, is one of the more famous recent cases. Keith Ingham and Charles Wilson’s design for the influential Building Design Partnership was constructed between 1968–69, and its extravagant monumental moulding could be Brasília rather than Britain. Four storeys of car parking protrude above the bus station, which forms a kind of street-length clamshell of ribbed, upward-curving balustrades. The design concept came not from the architects but from engineers at Ove Arup. With its broad, generous internal spaces, the building feels more like an airport lounge than a bus station. It represents a real attempt at providing the people of Preston with top-quality public building rather than the quiet accidents or bland leftovers we’re more used to in today’s amenity design. It’s currently being renovated.

Property developers Urban Splash are very slowly renovating those gritty streets in the sky at Park Hill estate in Sheffield. Here, council housing at one end of the estate has been made over into a mixture of luxury and lower-cost apartments while the majority of the site remains boarded up. Old graffiti has been rendered in flashy neon, a logo drawn from a cry of heartbreak, and there’s talk of a design museum taking up part of the site. It’s a strange resurrection, and not one that sits too sympathetically with the building’s past. But then again, one of many copycat schemes, the Hulme Crescents (1964–72) in Manchester, is long since lost, after a gradual descent from dangerously designed family council housing to an adult-only zone, then to art squats and, finally, uninhabited. Demolition followed in 1994. The Crescents contained design and construction flaws that weren’t common to Park Hill, and so the Sheffield scheme remains.

One modern British building to have maintained high standards of quality over the years is Denys Lasdun’s Royal National Theatre (1967–76), on the South Bank of the Thames. Its continued maintenance and development is probably the difference between commissioning flats for a working class district of Manchester and a national arts centre in central London. Lasdun hated being lumped in with the brutalists but – well, tough luck. His love of sculptural gestures – ziggurats, geometric landscapes, complex splayed towers – meant the kind of bold diagonal or horizontal shapes that were perfect to be rendered in that most plastic and malleable of materials, raw concrete. Like all the most successful architects of the age, he was in a position to get exactly what he wanted from engineers and builders and, also like most, he was an exacting, niggling boss. The National Theatre shows why this fastidious attention to detail was so important, and has resulted in the construction of a truly magnificent building. Everything has been worked through exhaustively, from the kind of stone and aggregate used in the concrete to best reproduce the boardmarks of the wood, through to the lighting – both inside and out – that would best bring these spaces and surfaces to life, creating intimate zones in what could have otherwise been an overwhelming and chilly megastructure.

You can see just how good the National Theatre is when compared to its neighbour, the IBM building (1978–84). Also designed by Lasdun’s practice, it was intended to be a complementary building to the theatre. For sure, there are some continuity features – the long, low concrete balustrades, for example – but on the whole this is a selfish use of the plot and the space. Sloped surfaces at ground level push passersby away from the edge of the building, and the vast outdoor decks overlooking the river remain unused on even the busiest of days. One of the most noticeable differences is that the IBM building is made from prefabricated concrete panels rather than the expensive boardmarked in-situ poured concrete of the theatre. Mimicking such a well-made building in cheaper materials and aping the generous social space with a network of unused private plateaux, the IBM building is an example of how not to extend an idea sympathetically.

Like the Barbican, the National Theatre has undergone a couple of extensive maintenance and adaptation phases since its completion in the mid-1970s. The most recent began in 2013: the NT Future project was taken on by architects Haworth Tompkins, with a brief to ensure it was being used to best of its potential. A new theatre space, the Dorfman, was constructed, as well as a series of workshops in an adjoining building. The front of the theatre was remodelled, with sympathetic new glazing to transform what had been storage areas into cafés and restaurants, and a piazza created on the previously blind north-east corner. Lasdun had high hopes for the long, low horizontal outside terraces he had created on decks above ground as ‘happening’ new social spaces for the city, but the inaccessibility of these platforms from outside limited this idea. But the new piazza now helps the intimate people-focused interior scheme (part of Lasdun’s original design) spill out onto the South Bank at ground level, connecting the building to its riverside setting as never before.

This is the finest piece of extensive restoration and subtle remodelling I have seen on an important brutalist building. The care and attention to detail has brought the National Theatre even closer to its original intentions than the, sometimes compromised, original layout had allowed. Subtle new lighting brings forgotten corners to life. Prints of the original shuttering were taken to ensure that any new construction was as seamless as possible, and the tones of the original soft furnishings were kept throughout. Here is raw concrete at its luxurious, startling, humanized best. The unparalleled entertainment experience in the two main theatres has been enhanced, and it welcomes even more people into its open arms every day. This is a joyous success story, and a blueprint for anyone thinking of starting out on a similar restoration project.

Royal National Theatre, London, UK.

Architect: Denys Lasdun.

Of course, once restored these places never go back quite to what they were before. Their resurrection brings with it all sorts of contemporary concerns: new cafés at riverside level on the South Bank as well as on the fashionably raised decks of the 1970s; flats in Park Hill restored but attracting a new class of resident. The world spins around its axis, and these renovation projects are not some form of time travel back to how things were, or how they could have been. Rather they project an idea of the past, as interpretive as any of the great Shakespeare productions inside the National Theatre.