The discovery of pyrite in the infill material used for concrete floors in Menolly Homes' Beaupark housing scheme near Portmarnock may have been a first for Ireland, but the problems caused by this mineral substance are not new.
A 2004 report by the Canadian Mortgage and Housing Corporation analysed many cases of structural and aesthetic damage in houses on the south shore of Montreal, where concrete slabs heaved and cracked due to pyrite contamination of the hardcore.
Pyrite expands when it comes into contact with air or water, resulting in a swelling of concrete floor slabs. Of the 197 cases examined in detail, the heaving varied up to 30 millimetres, causing longitudinal or star-shaped cracks in the concrete surfaces. The report recommended that the infill material should be replaced with another aggregate certified as "non-swelling" to overcome the problem, with pyrite "totally excluded" in the future. It also suggested using sulphate-resistant cement in all new houses.
A detailed booklet, ominously titled Pyrite and Your House - what home-owners should know about swelling backfills, was produced even earlier - in 1999 - by the Montreal-based Association des Consommateurs pour la Qualité dans la Construction.
Menolly Homes became aware of the Canadian experience and flew experts to Toronto to get briefings on how to deal with the pyrite problem in Beaupark, where some 200 homes - completed only last year - are said to be affected by swelling floors.
Apart from Beaupark, excessive levels of pyrite have been found in the Myrtle housing scheme in Baldoyle and Drynam Hall in Kinsealy - also built by Menolly Homes - and the company has initiated a High Court case against the infill suppliers, Irish Asphalt.
"The vast majority of houses that have been tested have come back positive for the presence of pyrite and many more householders are expecting the worst," said Labour councillor Seán Kenny. "No one has been told what actually is required to rectify the problems." Tommy Broughan TD (Labour, Dublin North East) has tabled a Dáil question to Minister for the Environment John Gormley asking what his department is doing to deal with the matter, and Dublin City Council's engineers are also looking into the Beaupark pyrite eruption.
In Canada, householders affected by the problem are eligible for financial assistance to cover the cost of replacing the floor slabs and underlying concrete fill in a damaged building with new pyrite-free materials - though garage floor slabs are excluded.
In a programme managed by the Societé d'Habitation du Quebec, the provincial government provides at least 62.5 per cent of the grant-aid, with the Canadian federal government contributing 25 per cent and participating municipalities the remaining 12.5 per cent.
