Sweet music to our ears

It's an unwelcoming building that houses a venue with notoriously poor acoustics. But the Royal Festival Hall is having a £70m makeover, details of which will be announced shortly. Jay Merrick gets a sneak preview

London's Royal Festival Hall has revealed details for three new phases of development that will transform the South Bank's Modernist architectural icon into a vastly more user-friendly arts facility. It's going to cost at least £70m, and will bring to an end the five-year odyssey-cum-migraine suffered by the site's mild-mannered masterplanner, Rick Mather.

The makeover of the Hayward Gallery's reception area, and the replacement of the grim, mean-spirited corkscrew stairs at the south-west approach to the hall with a flight of wide steps up to Hungerford Terrace, was a start. But now we have a much clearer glimpse into the future, which will see reinstated key elements of the building's original 1951 Festival of Britain form.

It is not all sweetness and light. There are still serious question marks concerning the future of the Jubilee Gardens site, next to the London Eye, and the grubby car park next to it. More on this thorny subject later.

First things first. In March, preparation work begins on the site's first major architectural addition, designed by Allies and Morrison: a four-floor building with the top two-and-a-half storeys running across Hungerford Terrace at right angles to the river. The cost: more than £10m, raised from private sources by the Festival Hall.

This glass-and-steel building, clean-limbed and unfussy in its details, will contain RFH offices and storage space. It's not a stunner - but it shouldn't be. The Festival Hall is queen of the site, and over-pushy architectural competition is out of the question. The key thing this new building will do when it's completed in June 2005 is remove the visual grot of Hungerford Bridge from view, and segue cleanly into Lifschutz Davidson's striking, if rather over-complex, footbridge.

At the same time, work begins on the remodelling of the Festival Hall's lower-ground floor, which contains the box office and a restaurant. It's not so much remodelling as reversion: the lower-ground floor will be "oversailed" by a new floor plate, which will allow full-width access into the foyer's promenade level from the terrace overlooking the Thames - very much nearer Sir Robert Matthew and Dr Leslie Martin's original architectural vision.

It's an intelligent move and nothing to do with purist sentiment. Allies and Morrison will, in effect, turn much of the north-facing foyer zone into a wide-open internal plaza, giving it a far more welcoming and spacious vibe, and allowing visitors to take in the building's internal architectural form much more clearly. The architectural clutter-busting will also allow the creation of new café and retail zones.

The third phase of work concerns the Festival Hall as a whole, and will see its closure - apart from the terrace-side foyer area - just as work on the extension building and north-entrance levels ends next year. And it'll be a huge undertaking, sucking in at least £40m from the Heritage and Arts Council Lottery coffers, and about another £20m from Festival Hall sources.

Ultimately, it's a glorified renovation job. But there will be at least three aspects of it that will make important physical differences to the building. First, the Waterloo entrance on the eastern flank of the building will be fully reinstated. That means a wide new bay of entrance doors and a large, uptilted canopy.

It's a respectful enough nod to Matthew and Martin's original design and is expected to bring many more into the Festival Hall from that quarter. One certainly hopes so, because the eastern façade is delightful - but one doubts it: there's something rather mordant about the ground-level space on that side of the building.

In any case, the vast majority of people coming to the hall approach the place from the direction of Waterloo station and the Thameside terrace. But who knows: perhaps the wide, new flights of steps from the top terrace down to the Waterloo entrance may make a difference.

Inside the building, the architects have opened up swathes of space on levels four and six. The former is largely bottled up with offices, and their removal will add spacious new comfort zones and bars. There are to be two roof gardens, which will occupy the east and west terraces on level six. The east terrace is currently unused; the west is roofed and contains offices. The revamped terraces will be partly glass and will be accessible, if desired, via the new glass lift on the interior of the building, in effect inside the east façade. Other changes, though less dramatic, will make a huge difference. Three words in particular seem welcome: stylish new washrooms.

The work on the Grade I listed Festival Hall will continue until its scheduled reopening at the end of 2006. And it's comforting to know that a key player will be Di Haig of Allies and Morrison, who actually studied under Leslie Martin. Comforting, too, that action is being taken to clean up the Festival Hall's salient deficiency: the irritatingly muddy acoustics that in this writer's experience have ruined everything from Hadyn violin concertos featuring Yehudi Menuhin to Miles Davis's electric bands. Solution: out goes the organ, the stage becomes narrower and deeper, the US acoustician Larry Kirkegaard installs a new and adjustable configuration of overhead panels, and "harder", more sound-reflective carpeting - 33,000 square feet of it - and seat upholstery are fitted.

The physical future and architectural integrity of the Festival Hall look safe enough. Less certain are the futures of the Jubilee Gardens and the adjoining car park. These may not seem to be significant architectural issues. Actually, they're massively important. In effect, several acres of prime riverside land are more or less duff. They add nothing significant to the stretch of ground linking the London Eye to Hungerford Bridge.

It's a wonderful brownfield-site development problem, and one that Rick Mather has so far failed to solve. Politics, potential cost and a lack of effectively persuasive consultation scuppered his attempt to redevelop the gardens. He picked a plan by Adrian Geuze of the trendy West 8 practice in Rotterdam, but it fizzled out. And proposals by Rafael Viñoly and Foreign Office Architects for the car-park site are on hold.

Now, though, it looks as if the Jubilee Gardens stand a good chance of being properly revived. The site has been handed to a new trust, driven originally by Mike McCart, the Festival Hall's communications director, and Paul Lincoln of the South Bank Employers' Group. The key point here is that planning and public-consultation issues can be dealt with far more smoothly. Any plan put to Lambeth Council by the trust will stand a far better chance.

And chances must be taken. The gardens must be recast by an architect or designer - Thomas Heatherwick springs to mind - who will deliver a 2.5 acre gem to the South Bank. No definite link between the gardens and the car park has been proposed, but it seems logical to maximise the impact of the gardens by extending them over the car-park site. The result could be a beautifully sculpted space. One hopes that when the trust draws up its shortlist of architects and designers it goes for those most capable of bringing something new and completely revivifying to this important public space.

Correction: in a recent article on Hampstead Theatre, I referred to the building's cost. The figure was inaccurate. The actual construction-cost of the building, designed by Bennetts Associates, was £8.5m.