Warning over danger slates

Construction News 18/11/2004

BY TOM CULLEN

THE CONFEDERATION of Roofing Contractors is warning all its members to stop using a range of slates currently in place on thousands of properties across the country.

The move comes after Essex contractor Apex Roofing Services suffered widespread curling and buckling to slates it received from producer Cembrit Blunn (now known as Cembrit) - part of the Dansk Eternit Group in Denmark.

Some of the company's 'Zeeland' slates started to bend after installation during the wet/dry process, causing concerns that they could fall from rooftops.

Tests on the slates commissioned by Apex and carried out by the Stanger Material Science Laboratory in St Albans, concluded: "Excessive distortion of the slates could lead to fracture under certain conditions such as high winds, which could cause danger to the public from falling sections of the slate."

The findings have prompted the Confederation of Roofing Contractors to tell all members to stop using the Zeeland slates until further notice. It is planning a warning in its next newsletter and chief executive Allan Buchan said: "If we receive word from our members that many are suffering a similar problem with the slate, we will not hesitate in trying to have it removed from the market."

The results suggest that the slates tested have received insufficient weatherproof coating on the back resulting in high absorption of rainwater causing the warping effect.

Apex Roofing senior partner Roy Leader attacked a host of bodies for failing to act.He said: "Cembrit Blunn (now known as Cembrit), the National Federation of Roofing Contractors and the British Board of Agrement have known about the problem since late 2003 and to date the issue has largely been ignored.We wrote to the federation telling them of the problem and they had no interest.We took it upon ourselves to warn each member ourselves."

The Zeeland slate is one of four produced by Cembrit Blunn (now known as Cembrit) and its main selling point is its aesthetic qualities. Cembrit Blunn refused to comment but in a letter seen by Construction News written to Apex, the company admits to errors in coating the Zeeland slates. Following tests carried out in laboratories in Denmark Cembrit Blunn (now known as Cembrit) admitted: "An inconsistent application of back coating has made the slates more susceptible to curling ... following tests on slates removed from your site further improvements to the back coating process have been introduced and are planned. When the improvements are complete curling will be virtually eliminated."