Frank Auerbach: London Building Sites 1952-62, Courtauld Gallery, London

What a mess! But that's how it should be

The most intriguing work in the Courtauld Gallery's show, Frank Auerbach: London Building Sites 1952-62, is not a painting but a drawing, Study for Oxford Street Building Site. This, prosaically, depicts the new John Lewis department store under construction, the old one having been bombed in the Second World War. Auerbach, like centuries of painters before him, has gridded up his sketch in red crayon the better to transfer it to canvas. A contemporary photograph of the scene shows the half-finished John Lewis as a similar composition of grids, its steel frame a sign of both its modernity and its Modernism.

So far, so 1957. In the context, the words "grid" and "construction" might lead you to think that what we're looking at here is the art equivalent of Salter & Unwin's new building – a piece of straightforward Modernism that picks up on a pre-war tradition going back to the Bauhaus and, beyond, to the Constructivist experiments of Malevich, Rodchenko and Naum Gabo. The last of these – like Auerbach, a Jewish refugee from the Holocaust – had lived in England from 1936-46. Look at Study for Oxford Street Building Site and it is easy to assume that Auerbach is taking up Gabo's torch, excavating Constructivism from London's post-war construction.

Until, that is, you look at Oxford Street Building Site I and II, the paintings Auerbach worked up from his sketch. Like all his canvases of the time (and, indeed, since), the Oxford Street pair look like big splats of mud, their impasto – layers of crusty paint an inch thick – echoing the act of building in their own building-up. Conventional wisdom holds that, with these works, the young Auerbach was trying to blur the boundary between sculpture and painting by working in paint so deep that it looked sculptural. I'd say his aim was less rarefied than that: more simply, that he was setting out to capture a recently destroyed city in all its heroic muddiness.

In Auerbach's scabby surfaces, then, we see the history of London. What we see less clearly is the history of art. At the outbreak of war, two decades earlier, Kenneth Clark, then director of the National Gallery, had led an assault on abstraction, on the kind of International Modernism practised by Gabo. Abstract art, Clark held, was foreign and unpatriotic: what war-torn Britain needed was figuration. Artists such as Ben Nicholson and John Piper, both abstractionists in the 1930s, gave up abstracts and took to painting landscapes, plugging into a Romantic tradition identified, for good or ill, as "British". From this reaction rose the School of London, championed by the Marlborough Gallery and its eventual stars, Francis Bacon and Frank Auerbach.

And so what we see in the Oxford Street paintings is the aftermath not of one war but of two, the first military and the second critical. In his fascination with rebuilding – in his own attempts to rebuild – Auerbach raises the key question for post-war British artists: where do we go from here? What does modernity mean in 1957, and how modern can a painter – a London painter – be? Writing to an anonymous correspondent a decade earlier, Gabo complained that his work in Britain had always been stamped with the word "imported". "The coming generation will have to work hard and persistently on that obdurate spot of the English mentality if they are to meet the task which history may ask of them in creating the new world," he said. Now, history was asking Auerbach just that.

How you view the results is up to you. Historically, the Building Site canvases are as muddy as their pigment. Auerbach's choice of subject may hark back to Moscow circa 1919, but it also picks up on the home-grown, anti-avant-garde, sort-of-late-Impressionism of the Euston Road School. And there is more. In 1958 – right in the middle of the sketches for the Oxford Street series – Jackson Pollock had his first ever London show, at the Whitechapel Gallery. In the crustiness of Auerbach's impasto, you sense a yearning to be somewhere else – to jump ship for New York, maybe, as Gabo had done, and throw in his lot with the Abstract Expressionists. Most of all, you feel that Auerbach wants to be seen as that old-fashioned thing, a painter. Nothing signals painterliness better than inch-thick paint.

What I seem to be saying here is that the Building Site pictures are a mess, and that is true. Like their subject, they are over-full of history – of destruction and reconstruction, the old world and the new. But then that is how they should be, how they have to be. Building has never been tidy.

To 17 Jan (020-7848 2526)