A Complete Guide to Detecting and Eliminating Pyrite
Find out how to detect pyrite and permanently eliminate it with Bisson Expert.
The issue of pyrite is nothing new in Quebec. In 2019, more than 30,000 homes in the province were affected by pyrite (Protégez-Vous). Widespread in certain regions, pyrite affects buildings constructed in recent decades.
To eliminate pyrite and avoid serious problems, the professionals at Bisson Expert provide you with all the details about the dangers associated with pyrite and the signs to look for. This article will help you better understand this phenomenon and offer you long-term solutions to restore your peace of mind.
What is pyrite?
Pyrite is a mineral (FeS2) found in the fill material used in home construction. When exposed to moisture and oxygen, a chemical reaction occurs that produces sulfate and can form gypsum; as the gypsum crystallizes, it causes the stone to crack. This causes swelling, which leads to cracks and uneven surfaces in the concrete slab.
The weathering process is slow. Often, it doesn’t become noticeable until about ten years after construction. In fact, problems related to pyrite are more commonly found under the concrete slabs of garages and basements.
Pyrite in a garage
Pyrite in a basement
What are the risks associated with pyrite in a house?
Pyrite in concrete has numerous effects. It affects your home in 3 ways: structural integrity, indoor air quality, and resale value.
The dangers of pyrite to your house’s structural integrity
Pyrite causes gradual but significant damage to your home. The danger is greatest when the house’s load-bearing elements are weakened by swelling. It will first damage the floors, then the interior finishes.
The impact of pyrite on health
Pyrite does not pose a direct health hazard. However, cracks that form in concrete slabs can lead to increased humidity levels in basements. Radon, a gas that is harmful to health, can also seep through these cracks.
Moisture and mold tend to affect indoor air quality, which can cause allergies and respiratory problems, according to Health Canada.
The impact of pyrite on your property value
Pyrite also causes a decline in a property’s market value. Houses with pyrite issues are likely to deter potential buyers and reduce overall interest in the property.
This is why many homeowners in Quebec prefer to address the pyrite issue before putting their home on the market. By doing so, they avoid being subject to unfavorable negotiations during the real estate transaction.
Risk factors associated with pyrite
Numerous studies have been conducted on pyrite-related issues in Quebec. These studies have revealed certain common trends among affected properties, including their year of construction and specific geographic locations.
If a property is subject to the following risk factors, it may have a pyrite problem:
[ 1 ] Year of construction
Properties built in the 1980s may contain pyrite, although we have also seen cases dating back to before the 1970s.
[ 2 ] Geographic area where the materials originated
More homes affected by this problem are found in Montérégie, but a few cases have also been reported in the metropolitan suburbs, on the Island of Montreal, and on Île Jésus. Some quarries did indeed contain large amounts of this mineral, including some on the South Shore and east of Montreal.
Good to know: Since April 1999, the construction industry has voluntarily adopted the CTQ-M100 standard, thereby eliminating the risk of contaminated stones in new construction projects.
Pyrite: warning signs to watch for
Certain factors may indicate the presence of pyrite in your concrete slab. These signs should not be taken lightly:
- Uneven floors
- Cracks in the concrete slab
- Lifting of the concrete slab
- White powder near cracks in the floor slab
- Doors that don’t close properly
- Moisture in the basement
- Sulfation Index (sulfate concentration measured in the backfill)
As soon as you notice one or more of these signs, it is recommended that you have the fill analyzed to confirm or rule out the presence of pyrite.
How to confirm the presence of pyrite in a home?
The only reliable way to determine beyond a doubt whether the signs you’ve noticed in your home are related to pyrite is to have the backfill analyzed by a recognized laboratory, such as Sedexlab or Multitest.
They will conduct a visual inspection of the issues, collect samples, and perform laboratory tests. You will then know whether there is pyrite in the backfill on your property and can take appropriate action.
Getting rid of pyrite: Bisson Expert’s long-term solutions
To permanently eliminate pyrite, the concrete slab and all contaminated backfill must be replaced. This is a permanent solution, meaning the problems will not resurface after the work is completed.
Pyrite elimination works steps
STEP 1
We are removing the existing concrete slab to gain access to the backfill beneath it.
STEP 2
We are removing all of the backfill contaminated with pyrite, since it is the cause of the swelling.
STEP 3
We install an interior drain that carries water away and reduces moisture under your basement.
STEP 4
We backfill with DB-certified, non-expanding material, which eliminates any risk of recurrence.
STEP 5
We pour a new concrete slab to restore your floor’s strength and durability.
When and why should you contact Bisson Expert?
If you have confirmed that your concrete slab is contaminated with pyrite, contact us. As soon as you reach out to our customer service team, one of our specialists will schedule a visit to your property.
No matter the scope of the work, our team brings more than 70 years of experience to the job, and we’ll ensure that your property remains functional at all times for you and your family.
Here’s how your experience with Bisson Expert goes:
Visit from a technical representative
A member of our team will assess the size of the affected area, the symptoms, and the damage to provide a customized proposal for the work.
Presentation of the proposal
You will receive a clear and detailed document outlining the costs, implications, and steps required to replace the contaminated backfill.
Planning and start of work
Our team will take every precaution to protect your home and begin the work efficiently.
Pyrite assistance programs and financial aid
Unfortunately, in 2026, there is currently no program specifically addressing pyrite issues in Quebec. The Société d’habitation du Québec (SHQ)’s financial assistance program for homeowners affected by pyrite ended in October 2011.
However, pyrite removal work may be eligible for certain government grant programs. Since these vary from year to year and by municipality, it is advisable to check for eligibility before starting the work. For example, you could check the Rénoclimat financial assistance program to determine if your project meets their criteria.
Legal action in the case of pyrite
If you have purchased a home and discover a pyrite problem, you may want to consider filing a claim for latent defects against the previous owner. In this case, it is recommended that you consult a lawyer specializing in real estate law.
Depending on your situation, it may be more advantageous to bring your case before the Small Claims Division, which handles hidden defect claims where the value of the damages sought does not exceed $15,000.
Frequently Asked Questions (FAQ)
Q : Is pyrite harmful to health?
R : Pyrite does not pose a direct health hazard, but the cracks it causes in concrete slabs can increase moisture levels and lead to mold growth, which may cause allergies and respiratory problems.
Q : What are the signs of a pyrite problem?
R : If you notice moisture in the basement, a bulging concrete slab, doors that don’t close properly, or uneven floors, you may be dealing with a pyrite problem.
Q : How can I tell if my concrete slab is contaminated with pyrite?
R : The only way to detect pyrite contamination is to have the backfill analyzed by a certified laboratory.
Q : How do you eliminate pyrite from a concrete slab?
R : To get rid of pyrite permanently, you must replace the concrete slab and replace the contaminated backfill with DB-certified (non-expansive) backfill.
Q : Why should I choose Bisson Expert to solve my pyrite problem?
R : With 70 years of experience in foundation and structural repair, Bisson Expert is the oldest company operating in this field in Quebec. Engineering, machining, and quality control are all performed in-house by qualified specialists, guaranteeing you exceptional results from start to finish.