Property: Cracks in the housing market: Differences of professional opinion on subsidence can leave people trapped in houses they wish to sell, says David Lawson

TWO YEARS AGO, Paul Bater was in the process of selling his home when he noticed a bulge in the living- room wall. Peeling away the paper, he found a small crack. Today it runs through the whole house, which, needless to say, remains unsold.

Mr Bater at first thought the problem would be temporary. A couple of small trees in the garden were leaching water from the clay soil and making it shrink, according to his insurance company's assessors. 'The trees were only about seven feet high,' he says, 'so I hadn't thought they were a problem. I had them removed and thought that would solve everything.'

He was wrong. The insurer's engineer says no further work is needed apart from a little paint and plaster. His own believes the house is still moving. 'It can take eight to 10 years for soil to recover after being dried out - sometimes longer,' says Alan Harris of the consultant engineers Robert West & Partners. He believes the foundations need underpinning.

Many home-owners find themselves in this trap, forced to wait years for claims to be settled, and accuse insurers of deliberate obstruction to cut costs. Meanwhile, their homes remain unsaleable. Any potential buyer willing to overlook the cracks would find it hard to raise a loan. Insurers will not cover such houses and, without insurance backing, no lender will provide the mortgage. Mr Harris accuses insurance companies of taking money under false pretences. 'They are meant to be providing protection for this sort of thing, not causing an even worse problem.' Loss adjusters, who are supposed to provide independent judgement on damage, face accusations of collusion with insurers to delay or avoid payments.

Every home has a few cracks, but they are usually harmless signs of drying plaster, shrinking timber or bricks expanding and contracting between summer and winter. Real subsidence is so rare that it was not even considered worthy of insuring until 1971. Lenders began to demand cover only when renovation of old property became more common, says John Pryke, an engineer who has spent 40 years investigating such disputes, often for the insurance ombudsman.

People move more often these days and are more aware of defects. 'But most importantly, homes have become major investments, and damage affects saleability,' he says. Many experts treat cracks solely as an engineering problem. Because homes rarely fall down, repairs can be put off for years while tests are conducted. Meanwhile, the price collapses.

Persistent drought in the Eighties landed insurance companies with claims still running at around pounds 500m a year, according to the Building Research Establishment. And rainfall has brought little relief.

Trees are far more problematical than freak weather: 'They keep on growing every year,' says Mr Harris. An innocuous conifer in the garden might grow 10 metres in five years, sucking moisture from under the foundations. An oak or willow can affect soil in a radius of up to twice its height, yet a 10-metre beech might spread its roots only four or five metres. Removing the offending tree merely gives the soil a chance to recover and expand, creating further movement. The BRE is so concerned about tree-felling that it has set up a national database of areas most at risk.

Problems are most severe on clays, which are common across much of southern England. These can shrink and expand causing the ground to rise or fall by two or three feet - more than the depth of foundations on many homes built before the mid-Sixties. Newer property is more stable because building regulations insist on much deeper footings. Yet some insurance companies last year doubled premiums on homes in postal districts known to be over clay.

Experts are split about the degree of danger. Angmering Gorse, a firm of building surveyors which offers pounds 40 inspections inside the M25 area, says only around 10 per cent of cracked homes reveal subsidence. The Institution of Structural Engineers believes too much money is spent on shoring up buildings.

Insurance companies' engineers generally fight shy of expensive underpinning and often insist on monitoring cracks, to ensure movement has stopped, before authorising repairs. 'But the duty of care should be to put things right so an owner can sell,' says Donald Halstead, a structural engineer who has carried out thousands of inspections. 'I am totally opposed to leaving it for years to see if movement has stopped.'

For home owners such as Paul Bater who are caught in this crossfire, the options are prohibitive and soul- destroying. He has been professionally advised that his home needs underpinning, but the loss adjusters don't agree. To take his insurance company to court over delays could incur costs running into five figures. To do nothing, on the other hand, could mean that his home will remain unsold.

Contacts: Subsidence Claims Association, Jakobi & Co, 21 Bloomsbury Way, London WC1A 2TH.

(Photograph omitted)