Pyrite in Montreal Real Estate: What Every Buyer Needs to Know Before Purchasing a Home
Title: Pyrite in Montreal Real Estate: What Every Buyer Needs to Know Before Purchasing a Home
By Albert Laurin | Residential Real Estate Broker | Founder of Laurin Immobilier | Proudly Operating Under RE/MAX 2000
Looking for a house for sale in Montreal, Laval, or the South Shore? Don’t make an offer without reading this. If you're working with a courtier immobilier (real estate broker) and exploring properties in Greater Montreal, you must understand one of the region's most overlooked risks: pyrite backfill.
Pyrite is not just a mineral issue—it can become a structural and financial nightmare. At Laurin Immobilier, my mission is to ensure every buyer is fully informed, protected, and equipped to make smart real estate decisions. Here's what you need to know.
📍 The History of Pyrite in Greater Montreal
From the 1980s to early 2000s, many homes across Montreal, Laval, and the South Shore were built using crushed stone backfill from local quarries. Unfortunately, some of this rock contained pyrite, a naturally occurring mineral that reacts badly when exposed to oxygen and moisture.
Key affected areas:
- South Shore (Montérégie): Brossard, Longueuil, Saint-Hubert, Chambly, Varennes
- Island of Montreal: Rivière-des-Prairies, Pointe-aux-Trembles, West Island (Kirkland, Beaconsfield, DDO)
- Laval and select North Shore suburbs
Figure 1: Estimated pyrite-risk zones in Greater Montreal (example map; actual risk must be verified through lab testing).
The source? Quarries in the region that unknowingly supplied pyrite-rich backfill before updated construction regulations came into effect around 2003. Since then, reputable developers and inspectors have used DB-certified, non-expansive backfill to avoid future issues.
⚠️ What is Pyrite and Why is it Dangerous?
When pyrite (FeS2) is exposed to oxygen and moisture, it oxidizes and produces sulphuric acid and gypsum. This chemical reaction leads to:
- Expansion of the backfill, which pushes up the concrete slab
- Heaving pressure that cracks foundations and garage floors
- Visible signs: star-shaped floor cracks, uneven slabs, sticky doors, white powder (gypsum residue)
Figure 2: Pyrite expansion damage in a garage slab. Note star-shaped cracks and uneven surface.
🔎 What Are the Signs of Pyrite Damage?
If you're touring a home or already own one in a risk zone, watch for:
- Heaving or uneven slab floors in garages or basements
- Bulging concrete or pressure along the bottom of foundational walls
- Spiderweb or star-shaped cracking patterns in the concrete slab
- Lifted floor sections or sticking interior doors near the slab
In every case, if any of these signs are present, you should contact a licensed building inspector or structural expert to confirm whether pyrite is the cause. Only a certified pyrite test can determine the presence and risk level accurately.
Damage can progress slowly over years, but once active, it's costly to repair.
📊 The Importance of Testing for Pyrite
If you're buying a home built between 1980 and 2003, especially in the regions listed above, a pyrite test is essential. As a professional courtier with RE/MAX 2000, I ensure that clients include this test as part of their inspection process.
Key points buyers should know:
- Test Type: CTQ-M200 or IPPG-SPPI laboratory analysis
- Cost: ~$350–$850
- What It Shows: The "swelling potential" of the backfill
- Danger Threshold: Swelling index (IPPG) over 40 = high risk
🔢 Quebec Government Risk Standards (IPPG):
Index Range Risk Level 0–20 Low 21–40 Low–Medium 41–60 Medium–High 61–80 High 81–100 Extremely High If a house shows an IPPG over 40, it’s considered high-risk and often requires intervention.
❄️ Can Water Trigger Pyrite Expansion?
Absolutely. Water is the main activator.
Key risk factors:
- Poor drainage around the home
- Heavy rainfall or seasonal flooding
- Condensation under the slab
That’s why I always advise clients to verify foundation grading and basement humidity control systems during visits.
🚧 What Happens If Pyrite is Found?
Homes with active or high-risk pyrite require remediation:
- Excavation of the concrete slab (garage or basement)
- Removal of contaminated backfill
- Replacement with DB-certified aggregate
Cost: $10,000 to $25,000+, depending on scope.
This is why verifying pyrite before purchase is critical.
✅ Final Advice from Albert Laurin
At Laurin Immobilier, my goal is not just to help you find a home—but to make sure that home is safe, sound, and a smart long-term investment.
Before buying:
- Ask when the home was built
- Ask where the backfill came from (if possible)
- Get a pyrite test if the home was built before 2003
- Ensure proper drainage and basement ventilation are in place
If you're working with a courtier and buying in the Montreal, Laval, or South Shore regions, make pyrite verification part of your due diligence.
Questions? Need help finding a pyrite-free home?
Contact Albert Laurin at Laurin Immobilier, proudly operating under RE/MAX 2000. Your protection is my priority.
514-295-5469 Call-Text-Whatsapp
website: www.laurinimmobilier.com
instagram: @courtieralbertlaurin