The Dreaded "P" Word: Pyrite

Real Estate Sales Representative with RE/MAX ROYAL (JORDAN) INC. / Tanya Nouwens Inc. E8107

You've found the perfect home for you and your family. You and the seller have come to an agreement on price.  And as a responsible home buyer, you get the property inspected.  While in the garage, and then in the basement, the inspector says, "Hmmmm, those cracks in the floor may be due to pyrite. Better get it tested to know for sure."

At this point, you and the seller of the home will likely have one of two reactions:

"Pyrite?  What the heck is pyrite?"


"OMG, pyrite?!  My world has come to an end."

What is pyrite?

Pyrite is a natural mineral.  Traces of it are found in the rock used to make crushed stone which is used for backfill in construction.  Backfill is used under the concrete slab in the building of garages and basements.

What's the problem?

Pyrite oxidizes when it comes into contact with air (oxygen) and moisture (humidity).  Through a serious of chemical reactions under certain conditions, some of the crushed stone used in the backfill can burst.  When the backfill contains enough rocks that are reactive to pyrite, this can lead to the backfill swelling and to the concrete itself crumbling, swelling and/or cracking.  Interior partitions resting on the slab may also heave, which may in turn damage upper floors and partitions.

The swelling is usually worse in garages, where a thicker layer of backfill is used and the stones used in the backfill are compacted so that there is very little give between them.

How bad is it?

The potential damage caused by pyrite varies from case to case.  In some cases, it is severe, where door jams on upper floors come away from the walls, interior walls develop huge cracks, and the swelling or heaving of the concrete slab can be 6 inches (15 cm) high.

In other cases, a homeowner can have absolutely no idea there is anything unusual going on, because any damage caused by the pyrite in their home seems like regular wear and tear.

How quickly does the damage show?

On average, it takes about 10 years to see any damage from pyrite.

How do I know if I have pyrite?

Standard testing procedure is now in place to test for the presence of pyrite.  I've used the company Pyritest before.  They follow the established protocol for testing (CTQ-M200) and will take samples of the backfill in the basement and the garage back to the lab for testing.

The results of the testing will produce what's called the IPPG in French (or SPPI in English - pyrite swelling potential index).  This is NOT a pyrite percentage but rather an indication of the quality of the backfill material.  The IPPG ranges are as follows:

0 to 10: Negligible risk of damage foreseen due to swelling of the backfill

11 to 20: Low risk of damage foreseen

21 to 40: Low to moderate risk

41 to 60: Moderate to high risk

61 to 80: High risk

81 to 100: Very high risk 

Once pyrite is detected in a home, we are under a legal obligation to disclose that fact to buyers.

What regions are affected?

It used to be that problems associated with pyrite were found only in Montreal's Montérégie, particularly on the South Shore.  This is no longer the case, and we now see it in some Montreal West Island homes (among other areas), including parts of Dollard-des-Ormeaux and Beaconsfield.

Are all homes affected?

No. Pyrite is not generally seen in new construction nor in very old homes.  Most cases occur in homes that were built from the late 1970s to about 1990. And it depends on the source of the backfill used.

And here's the homework... 

The West Island is my territory, and as such I want to keep you, Montreal West Island home buyers and sellers, well-informed. 

I am not, however, a home inspector nor a general contractor, nor a geologist nor a lawyer.  I therefore want to provide you with the following links for really good information on pyrite so that you can read it, digest it and form your own opinions on the matter.

Helpful resources:

The Association des consommateurs pour la qualité dans la construction (ACQC or Consumers Association for Quality Construction) put out an exhaustive but easy to read document called Pyrite and Your House.

The OACIQ, which is like the governing body for real estate agents and brokers in Quebec, put out an article on pyrite with many helpful links.

Go Maison Inc. has some helpful FAQs on Pyrite (available in French).

And the Société d'habitation du Québec (the government department responsible for housing policy and programs), has some helpful information on how to figure out whether you may be eligible for some financial assistance to help cover the cost of repairs.

The same government department has produced specific examples of how much may be reimbursed up to what home value.

And finally, here's some information on the obligations of real estate agents and brokers when it comes to pyrite.  Remember, we have a legal obligation to disclose the presence of pyrite to buyers.

Originally posted at

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Tanya Nouwens

Tanya Nouwens Inc., Montreal Real Estate Broker and Canadian Staging Professional (TM) 


C. 514-919-8468

This blog is written with my opinions. My opinions are presented with accuracy but not guarantees. Copyright Tanya Nouwens - 2015. If you want to reprint parts of this, just email me for my permission at


Comments (8)

James Quarello
JRV Home Inspection Services, LLC - Wallingford, CT
Connecticut Home Inspector

Tanya, Your title caught my eye. I have heard of the M word (mold), A word (asbestos) but never the P word. Very intersting and obviously something I would not have to worry about in CT.

Nov 18, 2010 09:08 AM
Brian Rugg
Rugg Realty LLC Sun City Texas 512-818-6700 - Georgetown, TX
Sun City TX Real Estate - Georgetown, TX Real Est

Hello Tanya:


I  can honestly say I have never had Pyrite on my radar screen before now . Expansive clay soils yes, but Pyrite, no.

Nov 18, 2010 09:10 AM
Debra Harbaruk
Re/Max City Realty, Commercial Dr Condos - Vancouver, BC
Vancouver BC Realtor

Interesting, I have never heard of it. I guess it is true when they say "You learn something new everyday"!

Thanks for sharing.

Nov 18, 2010 09:18 AM
Paul Chadwick
Baird and Warner - Saint Charles, IL

Tanya, really interesting.I love to learn new things!

Nov 18, 2010 09:24 AM
Paul Lesieur
203kloanmn - North Oaks, MN

Wow, never heard that before. And I thought I had it all covered.

Nov 18, 2010 09:59 AM
Susan Haughton
Long and Foster REALTORS (703) 470-4545 - Alexandria, VA
Susan & Mindy Team...Honesty. Integrity. Results.

Ditto, ditto, ditto.  I have never heard of pyrite, either.  Will be interested to see if anyone pops up who has had experience with it. 

Nov 20, 2010 03:58 PM
Tanya Nouwens
RE/MAX ROYAL (JORDAN) INC. / Tanya Nouwens Inc. - Montreal West Island, QC
Montreal Real Estate Broker & Stager

Hey there folks. I've been told anecdotally that most homes with pyrite had crushed stone that came from a particular quarry in Quebec. Nothing "official" that I've read states that officially, but one of our real estate trainers made this point when I was in training. If it's true, none of you likely have anything to worry about :)

Nov 23, 2010 05:24 AM
Bob "RealMan" Timm
Ward County Notary Services - Minot, ND
Owner of Ward Co. Notary Services, retired Realtor

Thank you Tanya. Now I need to get on the ball and see if it effects homes in my area.

Nov 23, 2010 08:23 AM