Fine Gael's Shane McEntee has told the Oireachtas Transport committee that two homes had exploded because of the inappropriate use of pyrite in their construction.
Mr McEntee said this happened in Kentstown, Co Meath, to houses worth €500,000 each.
He said he had been involved in a campaign to help the families and their homes were now being fixed up.
Pyrite is a mineral that expands in the presence of moisture and oxygen and is sometimes used in construction.
Mr McEntee said there were thousands of home-owners in Dublin, Kildare and Meath who were desperate, as their homes had been damaged due to the use of pyrite.
He said the builders' insurance company HomeBond had been reported to be dealing with 20,000 cases of homes where the floors had swelled.
The builders were not in a position to help and the builders' insurance policies did not cover it either.
Mr McEntee had asked the National Roads Authority if pyrite had been used in the construction of the M3 motorway and was told there was no evidence that it had.