Find out more about the pyrite solution. Bisson Expert will explain what to do if your foundation contains pyrite and how to eliminate it and to strengthen the foundation.

The pyrite phenomenon is nothing new in the province of Quebec. Widespread in some areas, pyrite can adversely affect buildings constructed in recent decades. To deal with this issue and to avoid serious problems, here is some useful information. It will help you to better understand the phenomenon and the only solution that is available to overcome it.

What is pyrite ?

Pyrite is a mineral (FeS2) found in the backfill material used during construction. When it comes into contact with moisture and oxygen, a chemical reaction produces sulphate and can turn it into gypsum, and crystallisation can cause the stone to shatter. Expansion then occurs, also causing the concrete to expand and crumble. It is a slow process that is noticeable only after ten years or so. Pyrite under garage and basement slabs is even more problematic

Is pyrite a health hazard ?

Yes, but not directly. The amount of sulphuric acid produced by pyrite during the chemical reaction is negligible, according to the Public Health Department of the Montérégie. The adverse effects of pyrite could however increase the level of humidity in basements as a result of the cracks that appeared in the slab. It is therefore very important to remain vigilant when traces of mold start to develop because they could adversely affect the indoor air quality.

What are the risks ? OR What are the risks of having pyrite ?

Pyrite causes progressive damage to the property. Over time, it damages the interior finishes such as the floor coverings. The risks are higher when the load-bearing members are weakened due to expansion. If the house is exposed to progressive damage due to pyrite, immediate action should be taken. Furthermore, if you are planning to renovate your house, keep in mind that it makes good sense to address the pyrite problem before tackling the renovation. Otherwise, you may just see your investment go up in smoke.

Pyrite can also depreciate the market value of your property. In fact, a house with pyrite problems is very likely to dampen the interest of potential buyers. This is why many owners prefer to tackle this problem before putting their house on the market. This way, they avoid exposing themselves to unfavourable negotiations during the real estate transaction.

What signs should you look for ?

  • Signs of sulphatization
  • Humidity in the basement
  • White powder on the cracks located near the slab
  • Doors that are hard to close
  • Cracks in the foundation
  • Floors that are not level

As soon as you notice one or more warning signs, you should find out if your house is at risk.

Risk factors :

Numerous studies have been conducted on pyrite. They have identified common trends in the properties affected by problems due to pyrite. If in doubt, you can determine whether your property is subject to the following risk factors :

  • Year of construction : Properties built in the 1980s, but we have seen pyrite problems in houses built in the 1970s. Since April 1999, the construction industry voluntarily complies with Standard CTQ-M100 that eliminates the risk of using contaminated stones in new buildings.
  • Geographical area where the materials come from : There are more houses adversely affected by this problem in the Montérégie area. However, some buildings have also been identified in the metropolitan area, on the island of Montreal and on Île Jésus. In fact, many quarries had lots of this mineral, some of them located on the South Shore and in the east end of Montreal.

Final step : pyrite testing

The only way to find out beyond any doubt if the warning signs are related to pyrite is to ask a renowned laboratory, like Sedexlab or Multitest for example, to test the backfill. They will perform a visual survey of the warning signs, collect samples and test them in their laboratory. Results will tell you if the backfill on your property contains pyrite.

How can you eliminate pyrite ?

Contact us if the laboratory results confirm the presence of pyrite on your property, regardless of the IPPG (expansion index). Bisson Expert is well known for the quality of its services and knowledge in this field. As soon as the Customer Service Department gets the information, one of our experts will start planning a site visit to perform the following :

  • Site inspection: Our expert will analyze the pyrite test results, check the size of the area that is affected and recommend a comprehensive solution.
  • Solution : Our expert will provide you with a detailed report that describes the cost, the work and all the steps that must be completed to replace the contaminated backfill
  • Planning and commencement of work : Our team will take all the necessary precautions to protect your house and efficiently carry out the work.

The only solution to pyrite related problems.

To permanently eliminate pyrite, all the contaminated backfill under the concrete slab, down to the foundation footing, must be replaced. The work primarily consists of clearing the entire area, breaking and removing the concrete slab currently installed, removing all the backfill and replacing it with new DB certified crushed stone (non-swelling).

This is a permanent solution, which means that the problems will not come back years from now. This is however an expensive solution and the price will vary according to the quantity of stone that must be removed. The work usually ranges from one week to one month. Removing pyrite from an entire basement will take more time than removing it from one small section of the garage.

Photo showing how a new slab is made and finished :

Regardless of the scope of the work, we will see to it that your property remains functional for you and your family. For example, removing pyrite from the basement of a single-family house requires demolition and reconstruction work, thus depriving its occupants from a vital space. Thanks to our expertise and our efforts to minimize the impact of the work site, the house will remain functional and liveable during the entire project. You will be able to safely stay in your house.

The importance of taking immediate action :

The longer you wait, the more the pyrite will expand and cause significant damage to your property. The structure of the house could also be adversely affected depending on its construction members. To protect your investment and stop the problem from getting worse, contact us without delay.

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