London's other hi-tech bridge

Lord Foster's Blade of Light, for ever the legendary bouncing bridge across the Thames at Bankside, reopens in a week or two. Its engineers, Arup, still denies that the design could have been right first time and, in a show of chutzpah whose flip-side is surely the purest bathos, has invited the great and good to attend the premiere of a specially commissioned piece of classical music by Sir Peter Maxwell Davis.

They can't afford that sort of thing in Newham. But they, too, have a fine bridge, in Plashet Grove, just round the corner from East Ham Underground station, built for the cost of just two or three of the hi-tech dampers that have nannied the Millennium Bridge into physical and legal submission.

No sign of Maxwell Davis on Tuesday afternoon in High Street North, East Ham. Bags of local east London chutzpah on show, though. Notably, the passage of two immaculate stretch limos and a stretch hearse whose white oak coffin bore a huge floral tribute that proclaimed: "Mum". If a thing's worth doing, it's worth doing right.

Which seems to be the case at Plashet School, a "beacon" comprehensive with a high percentage of Muslims among its 1,300 girls. Here, where English is taught as an additional language, classical music and floral tributes are not likely to be high on the agenda. But art has a notable presence. Wall displays reveal the pupils' creativity: pattern work by year-eight, "influenced by the artist Gustav Klimdt and the architect Antoni Gaudi [sic]"; and another board, whose pinned-up work in progress included a riff on Lord Foster's Truman Show roof over the British Museum's Great Court.

That Foster-Gaudi combo is a nicely pointed coincidence, for this school, whose two buildings are separated by the busy Plashet Grove, is locked together by something that has become a local landmark as iconic in its way as the Millennium Bridge. The 70m-long Plashet School footbridge is a sterling example of fine, high-impact design at low cost. Its blue steel frame, sculpturally twisted pillars and hooped, wagon-train Teflon canopy cost a bit more than £500,000.

The bridge looks sensational – there's a touch of Gaudi in the organic expression of its serpentine canopy – and it's as tough as the warships that used to be constructed at the Royal Docks, a couple of miles away. In East Ham, they know what hammers and rivets are for.

When the footbridge was completed, a year ago, it caused few ripples outside E6, because another bridge had, with some justification, captured the flood tide of media attention. Nevertheless, the Plashet span, designed by Birds Portchmouth Russum Architects, made its virtuous way into the Royal Institute of British Architects' "50 buildings of the year" list. The judges considered it "a brilliant architectural solution to an everyday problem", whose sinuous, rising form "reconciles effortlessly the different floor levels of the two buildings it connects."

For Mike Russum, the brief was literally uplifting. Forget the budget – it was clearly a wonderful opportunity to pull off something unexpected. And there was a ready-made cue to architectural aspiration on site.

The older of the two school buildings is not a head-turner. It was built in 1932 and originally named the East Ham Education Committee Grammar School for Girls; a modernist-lite kind of building, it is tidy of line but of little aesthetic merit. Over the road, though, is Plashet School's seven-storey north block. And that is a different story.

Designed by McMorran and Whitby in the Sixties, it cuts a dash that could only have been the result of realistic local authority spending and planners who were open to new ideas. The block is cruciform in plan, the core formed by two wide staircases. The four wings coming off the core contain classrooms, common spaces and offices. And it was full of light even on a dullish February day because of the large and satisfyingly scaled runs of its window panels. This building is worth looking at on its own.

Except that it's not on its own. It's tied to the south building by a blue-and-white caterpillar held up on four slim, artfully twisted steel supports. This type of structure – only a step or two removed from the kind of raw, conceptual idea that some architects would ditch as too risky – does not come easily in terms of detailed design: the Plashet School footbridge is as much a hi-tech organism as the Millennium Bridge. True, it may not have the Blade of Light's perfectly pared-down, symmetrical vibe; but, when you remember the small change that paid for it, the East Ham footbridge is absolutely in the same league of architectural and structural adventure.

How do you make a bridge that rises from the first storey of one building, curves in a slim "S" around a tree and then straightens again before entering another building at second-storey level? A bridge, moreover, whose canopy is a kind of asymmetrical accordion? Well, you activate your CAD-CAM design software, for a start. But you can do that only once you've solved the basic structural requirements.

The architects simply reverted to methods that, locally, were once bred in the bone. The structure is not so very far removed from elements of shipbuilding and tram-making. It is solid and clean in its detailing. The main carriage beam was formed from two 915mm-deep universal beams; they were joined by a welded steel-plate floor to create a monocoque section. Shades of HMS Warrior, Britain's first steel warship, which was bashed and riveted into shape by local muscle more than a century ago.

But it took Yorkshire muscle – "this huge 20-stone bloke", according to Russum – to hammer two crucial "locking" steel wedges into the large pins that clamped the bridge to its two central pillars. Doncaster, where the bridge was prefabricated, supplied more than sinew: apart from the translucent canopy and integral drainage systems, the bridge's most interesting aesthetic touches are found in its supports. They were formed from thick sheet steel, cut and twisted to make symbolic palm-tree silhouettes. Ten years ago, such twisted geometry would have been a massive and expensive challenge. Not any more. The computer-designed forms were simply e-mailed to the Doncaster steel specialists, who fed the binary data into automatic laser cutters. Result: elegant, millimetre-perfect columns.

And it's the kind of perfection that reminds us that surprising and brilliantly realised architecture is possible anywhere and for any reason. It reminds us, too, that life at the cutting edge can be as gripping in E6 or Doncaster as it is in the shadow of Tate Modern.