Expert says infill 'totally unsuitable'

THE MATERIALS used to make infill for 750 Dublin homes, which subsequently developed cracking, was “fundamentally a poor quality rock” and “totally unsuitable for use as a construction product,” an engineering expert told the Commercial Court yesterday.

Dr Michael Maher, a geotechnical engineer with Golder Associates, said the infill under the homes at Drynam Hall in Kinsealy, Beaupark, Clongriffin and Myrtle in north Dublin showed definite signs of chemical breakdown.

Mr Maher was giving evidence in a case taken by four companies, Hansfield Developments, Viking Construction, Menolly Properties and Menolly Homes, belonging to house builder Séamus Ross against three companies in the Lagan Group. Irish Asphalt, Lagan holdings Ltd and Lagan Construction Ltd supplied the aggregate, or crushed rock, for the infill used in the houses. Mr Ross is seeking indemnity of up to €60 million against actions for damages from the householders whose homes developed defects.

Mr Maher told Justice Paul Gilligan he was asked to examine one house in Drynham Hall in March 2007. It had developed cracks in the livingroom floor, kitchen and a partition wall. Asked by counsel for Mr Ross’s companies, Brian O’Moore SC, whether foundation settlement could be the cause of the cracks, Mr Maher said he could find no evidence of that.

“Foundation settlement would manifest itself by movement around the perimeter,” he said. There was no cracking of the external walls and there was evidence that the concrete slabs on the floor had moved independently of the foundations and walls of the house, he said.

He also ruled out the possibility that the concrete slabs used on the floor had been subject to shrinkage. He said shrinkage tended to happen early in the life of the concrete when it dried out, it followed a specific pattern and would not cause vertical movement. The slabs at the house he examined “had all the evidence of being pushed up”.

Laboratory testing of the infill samples showed the aggregate used had definite signs of some kind of chemical breakdown or reaction, Mr Maher said. Pyrite contained in the material had oxidised, turned to acid and reacted with calcium carbonate, causing gypsum crystals to be deposited.

“This is a recipe for significant problems, specifically swelling of material,” he said. Further studies on infill samples from houses in all three developments showed similar materials had been used, Mr Maher said. The infill tested did not comply with standards set down by the National Roads Authority for the material it uses beneath motorways, he said. Its ability to absorb water was too great and it was too easy to crush.

“The material was fundamentally a poor quality rock to be making an infill material from.” The more porous a rock, the more likely it was to degrade, he said, and the rock in the aggregate had a very high degree of water porosity. He said the material was characteristic of a mudstone, “a poor quality material which would not be used as a construction aggregate”.

“It was totally unsuitable for use as a construction product.”