Sugar’s Amsprop City Properties is suing surveyors, Wilks Head & Eve after its survey failed to pick up on the spread of ‘Regent Street disease’ onto a building Amsprop paid £5.9m for.

The disease occurs when moisture penetrates a Portland stone facade and rots structural steelwork, causing corrosion to steel frames.

Amsprop argues that the roof had to be stripped entirely, with new steel inserted before an asphalt roof could be laid, as a result of extensive corrosion

The frame-corroding condition was detected by workmen carrying out refurbishment in August 2006. It was found in the prime property; a restaurant and five floors of office space.

Wilks Head & Eve (WHE) 2005 survey made no mention of the damage, according to Amprop’s writ.

Amsprop said that if it had known about the damage: ‘A reduction in the sum of £300,000 could have negotiated to the purchase price. As a result, Amsprop is entitled to and hereby claims by way of damages from WHE the diminution in value of the property by reason of the corrosion of the steelwork supporting the roof.’

WHE charged £2,250 in February 2005 for a full structural survey of the steel-framed property but reported no significant defects. Structural engineers were also called to inspect it with a building contractor, but the problems were not reported, Amsprop said in its damages claim.

In its defence, WHE said the condition of the roof was ‘good’ at the time of the survey and denied the suggestion that £300,000 would have been knocked off the price.

Because of the ‘buoyant’ property market in 2005, it said: ‘The city of London is unlikely to have agreed a further reduction in price on account of any defects in the steel structure supporting the roof when the cost of rectifying the same was marginal in comparison with the price agreed with the property.’