Amid strong doubts about the economy, Coventry, one of the smaller societies, raised bad debt provisions to pounds 1.4m from pounds 400,000. Its overall provision rose to pounds 2.6m.
Martin Ritchley, chief executive, said: "We are looking ahead with a degree of caution. I hope that caution proves unfair.
"But the fact that we have had six increases in base rates, a flattening of house prices and people being laid off - in the manufacturing sector in particular - has made us cautious."
Yesterday this view was reinforced by data showing widespread gloom among surveyors over the state of the housing market. Fresh figures from the Royal Institution of Chartered Surveyors showed only 16.4 per cent reporting a rise in house prices in July - the lowest for more than two years.
The proportion of surveyors reporting an outright fall in house prices rose to more than 7 per cent in July. In the first six months of 1998 the number of homeowners looking to sell showed its biggest rise in three years.
Ian Perry, housing market spokesman for the RICS, said: "In the short term the Bank of England's commitment to bring down underlying inflation by maintaining interest rates at current levels will almost certainly slow housing market activity. But the key to an active market is consumer confidence - this fragile commodity has been steadily eroded over recent months and will not be helped by a further slowdown in economic growth during the rest of 1998."
The slowing market was most apparent in the South-east of England, where the number of surveyors reporting price rises fell by around 20 per cent.
Surveyors believe the market has now "gone off the boil" and blame poor weather and a traditional summer slowdown in the market. Many also noted a growing reluctance by buyers to pay inflated prices.
Coventry said it raised bad debt provisions due to economic concern rather than the safety of new loans. Customers were still avoiding arrears, it said.
The society made the bad debt provision despite a bumper result for the first six months of 1998, when profits rose to pounds 17.6m from pounds 11.5m in the first half of 1997.
A decision to remain a building society allowed Coventry to trim margins, the society said. Net lending doubled to pounds 324m and savings business quadrupled as customers were attracted by competitive rates.
More than three-quarters of the society's new borrowers were sold fixed- rate or discounted mortgages, many of them tying themselves to the lender for at least five years.