Pyrrhotite is a mineral that is present naturally in the ground. Because of its particular properties (it oxidizes upon contact with air or dampness, and it releases sulphuric acid that attacks cement paste), pyrrhotite should never, for obvious reasons, be present in the aggregate used in making concrete.

Unfortunately, pyrrhotite-contaminated stone extracted from a quarry in Quebec’s Mauricie region was used to produce the foundations of many hundreds of homes built between the late 1990s and the mid-2000s. Many homeowners in the Mauricie region, particularly in the Maskinongé and Les Chenaux regional county municipalities, along with some on the south shore of the St. Lawrence River in the Nicolet-Yamaska regional county municipality and the city of Bécancour, are having to deal with significant problems involving the presence of pyrrhotite in concrete that may weaken the load-bearing capacity of foundations.

A characteristic sign: Interweaving star- or cross-shaped cracks.

In response to this situation, which is leading to very substantial costs for the homeowners concerned, the Government of Quebec, through the Société d’habitation du Quebec, is offering financial support for conducting the necessary repair work. Here is how to get more information:

Société d’habitation du Quebec

News release issued on May 6 concerning financial support provided to residents facing problems related to the presence of pyrrhotite.


City of Trois-Rivières

The city of Trois-Rivières has added a complete and comprehensive section to its website on the pyrrhotite issue. It includes the application form for financial assistance for homes affected by pyrrhotite as well as the form for estimating and allocating costs for basement restoration work conducted by owners.


Coalition Proprio-Béton

Excerpt from the group’s website (translation from the French):

“The Coalition Proprio-Béton is a spontaneous group of victims who have decided to pool their efforts in seeking to enforce their rights and to obtain appropriate financial support from the municipal, provincial and federal authorities. The Coalition is also intended as a forum for victims to exchange views and information.”


La Facture, a Radio-Canada television program (in French)

Here is a very interesting report showing the scope of the damage caused by pyrrhotite. Broadcast in October 2010.


CAA-Quebec Residential Advisory Services

For more information on this specific problem or on other housing-related topics of interest, CAA-Quebec members can contact Residential Advisory Services free of charge by telephone at 1 877 803-1118.