Pyrite in Quebec: Cracks, Pyrite Testing, the IPPG Chart and What to Know Before Buying a Home

You are standing in the basement of a house.

Everything looks relatively normal.

Then you look at the floor.

One crack.

Then another.

Some of them seem to form a star-shaped pattern.

And immediately, one word comes to mind:

Pyrite.

At that point, two reactions are common.

The first:

“There's pyrite. I'm not touching this house.”

The second:

“It's just a crack. Every house has them.”

Either reaction can lead you to make a decision much too quickly.

Because a crack does not automatically mean pyrite.

And the presence of pyrite, or backfill with the potential to swell, does not automatically mean the property should be rejected.

Before deciding anything, there are better questions to ask:

What has actually been observed?

What has been tested?

What does the report really say?

What damage is currently present?

What remains unknown?

And most importantly:

What could the consequences be for you if you buy this property?

Because in real estate, the problem is not always the defect itself.

Sometimes the real risk is buying a problem you do not yet understand.

Here is what you should know about pyrite in Quebec, concrete slab cracks, pyrite testing, IPPG results, possible repairs and the decisions that may need to be made before buying or selling a property.

1. What is pyrite?

Pyrite is a mineral containing iron and sulphur that can be found in some of the stone used as backfill beneath concrete slabs.

The problem does not come simply from the fact that a piece of stone contains pyrite.

Under certain conditions, chemical reactions can occur within the backfill.

These reactions can cause the material to increase in volume.

When that backfill is underneath a concrete slab, the expansion can exert upward pressure.

Over time, this can contribute to:

• cracks in the concrete slab;
• sections of the floor lifting;
• deformation;
• damage to certain partitions or finishes;
• doors becoming more difficult to open;
• other forms of damage depending on the situation.

But an important distinction needs to be made immediately.

The presence of pyrite does not automatically mean significant damage.

And the opposite is also true:

Cracks in a concrete slab do not automatically mean pyrite.

That is precisely why an expert assessment matters.

Looking at a crack can raise a question.

It cannot, by itself, answer it.

2. What are the possible signs of a pyrite problem?

Certain signs may raise questions.

For example:

• star-shaped or web-like cracks in a concrete slab;
• heaving or bulging of the floor;
• cracks that appear to be changing;
• partitions that appear to have moved;
• doors becoming difficult to open;
• deformation of certain finishes;
• unusual differences in floor level.

But remember this:

A sign is not a diagnosis.

A concrete slab can crack for several reasons.

A floor can be uneven for different reasons.

A door can rub without pyrite being involved.

You can therefore observe something that deserves further investigation without knowing its cause yet.

That distinction is extremely important when viewing a property.

Your job as a buyer is not to become a geologist during the showing.

Your job is to notice enough to recognize when more questions need to be asked.

Observation should lead to investigation, not an instant conclusion.

3. Are certain areas of Quebec more affected by pyrite?

Pyrite problems are particularly well known in Greater Montreal and certain parts of the Montérégie region.

On the South Shore, cases involving swelling backfill have historically been documented across a broad area, including locations between Châteauguay and Varennes and between the St. Lawrence River and the Richelieu River.

Cases have also been documented in different parts of eastern and western Montreal.

But be careful with shortcuts.

A municipality located in an area historically associated with pyrite does not mean every house in that municipality is affected.

Two neighbouring homes could even have been built using backfill from different sources.

And a neighbourhood without a strong reputation for pyrite problems does not guarantee that an individual property has no issue.

The property itself needs to be evaluated.

Its backfill.

Its concrete slab.

Its visible signs.

Its history.

Its available reports.

You are not buying the geological reputation of a postal code. You are buying a specific property.

Location provides context.

It does not provide a diagnosis.

4. How is a pyrite test performed?

A proper pyrite assessment involves more than looking at a crack.

A specialized assessment generally involves taking samples from the relevant areas to analyze the backfill beneath the concrete slab.

Depending on the mandate and circumstances, the assessment may consider:

• the composition and characteristics of the backfill;
• its sulphatic swelling potential;
• chemical analyses when required;
• the condition of the concrete slab;
• observed damage;
• other information relevant to the building.

In Quebec, determining the Petrographic Swelling Potential Index, commonly referred to by the French acronym IPPG, is currently addressed by the BNQ 2560-500 standard.

For an existing building, however, an IPPG result should not be interpreted in isolation.

It should form part of an assessment that also considers a visual inspection of the building and the other information collected.

The garage and basement can also represent separate areas.

You should not automatically assume that a result obtained in one part of the building perfectly describes every other part.

Once the analysis is completed, you will generally receive a report.

And that is often where four letters start worrying homeowners:

IPPG.

5. What does IPPG mean?

IPPG is the French acronym for:

Indice pétrographique du potentiel de gonflement.

In English, it refers to the Petrographic Swelling Potential Index.

It is an index used to characterize the swelling potential associated with the backfill being analyzed.

And here is probably the most important thing to understand when reading the report:

The IPPG is not the percentage of pyrite in your backfill.

An IPPG of 40 does not mean:

“There is 40% pyrite underneath my concrete slab.”

It also does not mean:

“My slab is going to swell by 40%.”

And it cannot tell you exactly what will happen to the property or when it will happen.

The IPPG is an index.

That index needs to be interpreted alongside the other observations and findings in the report.

6. IPPG chart: how do you interpret a pyrite test result?

The following categories have traditionally been used within the CTQ-M200 framework to describe IPPG results:

This chart is useful.

Very useful.

But you need to understand what it tells you...

and what it does not.

Suppose the IPPG is 47.

According to this classification, the swelling potential falls into the:

medium-to-high category.

That does not mean 47% of the backfill is pyrite.

It does not mean the floor will swell by 47%.

And it does not mean a particular repair must automatically be performed.

The number needs to be considered in the context of the building.

The professional may consider factors such as:

• damage already observed;
• the condition of the slab;
• the nature and thickness of the backfill;
• signs of reaction;
• moisture conditions;
• deformation;
• known changes in the cracks;
• other findings from the assessment.

Now imagine two properties.

House A: IPPG 45

Significant damage is already visible.

The slab is heaving.

Some partitions appear to be affected.

House B: IPPG 45

No significant disorder is currently visible.

Same IPPG.

Not necessarily the same situation.

And that is the mistake buyers need to avoid.

The number may be identical while the buildings are telling two very different stories.

The chart helps you understand the potential of the backfill that was analyzed.

The complete report helps you understand the property.

7. Does a high IPPG automatically mean everything needs to be replaced?

No.

A high IPPG deserves to be taken seriously and properly understood.

But a decision about repairs should not be based on one number alone.

You also need to understand:

• the damage currently present;
• its severity;
• whether it appears to be progressing;
• the report's conclusions;
• professional recommendations;
• how the affected spaces are used;
• the potential consequences of not intervening.

A property can have backfill with significant swelling potential without necessarily showing exactly the same damage as another property with a comparable result.

That is why asking:

“At what IPPG do I have to replace everything?”

oversimplifies the issue.

A better question is:

“What does this IPPG mean for this specific property?”

That small change in the question can completely change the quality of the answer.

8. Be careful with so-called “pyrite percentages”

You may hear statements such as:

“There's 20% pyrite.”

“Below 20%, it isn't a problem.”

“Above 40%, everything has to be replaced.”

Be careful.

The IPPG is not a percentage of pyrite.

And a single number should not automatically become a real estate decision.

In the context of a promise to purchase, an arbitrary percentage or IPPG threshold should not be treated as a universal rule determining whether a buyer can automatically walk away.

Why?

Because the assessment needs to be interpreted as a whole.

The IPPG is one part of that analysis.

The visible condition of the property is another.

The conclusions of the professional matter.

The documentation matters.

The damage matters.

Do not turn a technical index into a universal real estate rule.

9. Can a house with a low IPPG still have cracks?

Yes.

And that is another reason not to focus only on the chart.

A crack in a concrete slab can have different causes.

Concrete can crack.

Soil can move.

A building can experience different forms of movement.

Previous work may have been completed.

Drainage or other conditions may also be involved.

You therefore want to avoid two automatic conclusions:

“There is a crack, so it must be pyrite.”

and

“The IPPG is low, so this crack does not matter.”

If the situation deserves further investigation, have it properly evaluated.

The number does not erase what the building is showing you.

And what the building is showing you does not replace the analysis.

10. What repairs may be necessary when a pyrite problem is significant?

When the situation justifies major corrective work, the project can be substantial.

Depending on the property and professional recommendations, the work may involve:

• removing certain finishes;
• demolishing the existing slab;
• removing the problematic backfill;
• excavating to the required depth;
• replacing the backfill with appropriate material;
• rebuilding the concrete slab;
• restoring partitions and finishes.

In a fully finished basement, this can obviously become much more complicated.

Flooring.

Walls.

Bathroom.

Family room.

Storage.

Electrical systems.

Plumbing.

All of those factors can affect the actual scope of the project.

That is why you should be cautious when someone says:

“It costs about X dollars to fix pyrite.”

Without knowing the property, that estimate may be almost meaningless.

An unfinished garage and a fully finished basement are not the same project.

Area matters.

Depth matters.

Access matters.

Damage matters.

Finishes matter.

The cost of correcting a pyrite problem is not simply the cost of removing backfill. It is also the cost of everything that may need to be removed and rebuilt to reach it.

11. Does a property with pyrite automatically need to be repaired?

Not necessarily.

Again, universal answers are rarely helpful here.

The decision can depend on:

• the potential identified;
• existing damage;
• whether that damage appears to be progressing;
• how the space is used;
• professional recommendations;
• the owner's plans;
• whether a real estate transaction is being considered.

A stable, documented situation is not necessarily evaluated the same way as a problem that appears to be progressing rapidly.

And when a property is being sold, another factor enters the picture:

uncertainty for the buyer.

Even if the current homeowner has lived comfortably with the situation for years, a future buyer may want to understand the risk before accepting it.

Because the seller's comfort with a situation does not automatically become the buyer's comfort with it.

12. What should a buyer check before purchasing a house where pyrite is suspected?

Start by looking for information that already exists.

Ask for documents such as:

• the seller's declarations;
• available pyrite reports;
• available previous inspection reports;
• invoices for completed work;
• before-and-after photographs;
• additional expert reports;
• documents related to previous repairs.

Then look at the report itself.

Do not stop at the IPPG.

Ask:

What was tested?

Where were the samples taken?

What damage was observed?

What did the professional conclude?

Were repairs recommended?

Is further investigation necessary?

In areas where pyrite-related problems have historically been documented, a specialized assessment can become particularly important when no report exists or the condition of the property raises questions.

In a real estate transaction, a promise to purchase can also be structured to provide for an appropriate expert assessment and review of its results according to the conditions agreed upon by the parties.

The objective is not to find a reason to be afraid of the property.

The objective is to know enough about what you are buying to decide whether you are comfortable buying it.

House A versus House B: which one actually represents more risk?

Imagine two properties.

House A

A pyrite problem was identified.

You have:

• the report;
• the results;
• photographs;
• invoices;
• a description of the work completed;
• available documentation about the repairs.

You know the history.

House B

You see cracks.

No test.

No report.

No invoices.

The owner does not really know what happened.

You are simply told:

“It's always been like that.”

Which house is automatically the better property?

There is not enough information to answer that.

But which one contains more unknowns?

House B.

And that distinction matters.

Because a known defect can be analyzed.

It can be professionally assessed.

The work can be understood.

Documents can be reviewed.

Potential costs can be investigated.

An unknown first needs to be turned into information before you can even begin to measure the risk.

That is why a property with a documented history of pyrite is not automatically riskier than one that has simply never been tested.

It depends on what is actually known.

And sometimes, what remains unknown is the most important part of the entire transaction.

Is a house with pyrite impossible to sell?

No.

But pyrite can influence a buyer's perception of risk, the decisions some buyers make and potentially the transaction itself.

A buyer may want to understand:

• the nature of the problem;
• existing damage;
• test results;
• completed work;
• future risks;
• potential costs.

For a seller, transparency and documentation become particularly important.

Quebec's seller declaration process addresses pyrite and certain tests and expert assessments concerning the property.

If you have a report, invoices or documents relating to completed work, gather them.

Now compare these two answers:

“Yes, there was pyrite, but everything was fixed.”

and

“Here is the report. Here is what was found. Here is the work that was completed. Here are the invoices and the documentation we have.”

Those two answers may describe the same property.

But they do not give an interested buyer the same information.

The second answer does not simply ask the buyer to believe the seller.

It gives the buyer information that can be reviewed.

Documentation does not erase the property's history. It replaces some of the uncertainty with facts.

And in a real estate transaction, reducing uncertainty can be extremely important.

Does pyrite automatically reduce a property's value?

No.

It would be far too simplistic to assign an automatic reduction in value to a particular IPPG result.

The market's reaction can depend on many factors:

• the extent of the damage;
• available documentation;
• work already completed;
• potential cost of future work;
• the property's overall condition;
• location;
• comparable properties;
• buyer perceptions;
• how much uncertainty remains.

One buyer may accept a documented situation.

Another may want no pyrite-related risk at all.

Another may be interested if the price reflects the work they expect to undertake.

That is why you cannot say:

“An IPPG of 40 automatically means an X% loss in value.”

There is no universal IPPG-to-sale-price conversion chart.

The technical number is part of the property's file. It does not replace a real estate analysis of the property.

What should a seller do if they already have a pyrite report?

Start by gathering your documentation.

The complete report.

Analyses.

Invoices.

Photographs.

Documents relating to completed work.

Additional expert reports.

Relevant information about repairs.

Then make sure the relevant information is properly addressed within the transaction and the declarations that apply.

Do not turn the report into something it does not say.

A low IPPG is not an absolute guarantee.

A high IPPG does not automatically mean catastrophe.

Completed repairs do not automatically mean no further verification will ever be necessary.

Present what is documented. Not what you would like the buyer to conclude from it.

That distinction can create much more clarity than trying to minimize the issue.

What questions should you ask the expert after receiving the report?

Do not ask only:

“Is it serious?”

It is an understandable question.

But it is so broad that the answer may not give you enough information to make a decision.

Instead, ask:

1. What is the IPPG?
2. What does this result mean for this particular property?
3. What damage did you observe?
4. Is that damage consistent with the behaviour of the backfill?
5. What area was tested?
6. Should other areas be tested?
7. Does the damage appear to be progressing?
8. Are repairs recommended?
9. What information remains unknown?
10. What would you want me to understand before making a decision about this property?

Notice something.

Only one of those ten questions asks for the IPPG number.

The other nine are trying to understand what that number means.

That is how a technical report becomes useful in a real estate decision.

Can you rely only on a pre-purchase home inspection to detect pyrite?

No.

A building inspector can observe visible signs and recommend further investigation when the situation warrants it.

But a visual inspection does not replace a specialized pyrite assessment.

The inspector may see the crack.

They may see the heaving.

They may see other visible manifestations.

But determining the characteristics of the backfill and its swelling potential requires appropriate analysis.

The distinction is important:

The inspection can raise the question.

The specialized assessment tries to answer it.

That is not a weakness of a home inspection.

It is part of understanding what different professionals and different types of investigations are designed to do.

Should you be afraid to buy a house with pyrite?

Fear is probably not the best analytical tool.

Neither is dismissing the issue.

Replace both with information.

If the problem is documented, understand it.

If repairs were completed, verify what was done.

If no test exists and visible signs raise questions, determine whether a specialized assessment is appropriate.

If the report contains an IPPG, use the chart to understand the category.

Then read the conclusion.

Look at the damage.

Ask questions.

And finally ask yourself:

“Now that I understand the situation better, is this a risk I am willing to accept?”

There is no identical answer for every buyer.

One person may accept substantial work if the price makes sense for their project.

Another does not want a major renovation under any circumstances.

One buyer may have a substantial financial reserve.

Another may be using almost all available cash to complete the purchase.

The same property can therefore represent a very different decision for two buyers.

That is why understanding the property matters more than finding a universal answer on the internet.

10 questions to ask before buying a property where pyrite may be present

Before making your decision, ask:

1. What signs have been observed?
2. Has a pyrite test already been performed?
3. Can I obtain the complete report?
4. What is the IPPG, and how does the professional interpret it?
5. Were the basement and garage assessed separately when relevant?
6. What damage is currently present?
7. Has corrective work already been completed?
8. Are invoices, photographs and documentation for that work available?
9. Is further expert assessment recommended?
10. What remains unknown after all these checks?

The tenth question may be the most important.

Because real estate decisions are almost never made with absolutely perfect information.

But there is a major difference between accepting uncertainty you understand...

and accepting a risk nobody has properly measured.

The crack is not the decision

Go back to that basement.

You are looking at the crack.

Maybe it looks like a star.

And the word comes back:

Pyrite.

At that exact moment, you may still have no idea what is actually underneath the concrete slab.

And that is the point.

The crack is an observation.

Not a conclusion.

The IPPG is an index.

Not a percentage of pyrite.

The chart is an interpretation tool.

Not a verdict on the house.

And a history of pyrite is not automatically a reason to buy or reject a property.

You need to go further.

What was observed?

What was tested?

What does the IPPG mean?

What damage is present?

What work has been completed?

What remains uncertain?

Only then should you ask:

“Now that I understand what I'm buying, does this property still fit the level of risk I'm willing to accept?”

That is where an expert assessment becomes truly useful.

It does not choose the house for you.

It does not promise what will happen in the future.

It does not turn a complex problem into a magic number.

It allows you to replace some uncertainty with information.

And when you are dealing with a property worth hundreds of thousands of dollars, that information can completely change the quality of your decision.

So do not let a crack make the decision for you.

And do not let one number reassure you too quickly either.

First understand what the building is telling you.

Then understand what the expert assessment is telling you.

After that, decide what you are genuinely prepared to accept.

Because in real estate, the best-case scenario is not necessarily buying a house that will never have a problem.

It is avoiding the purchase of a problem you did not understand.

The right decision. At the right time... For the right reasons.

Jonathan Cabana
Residential and Commercial Real Estate Broker
eXp Québec
Greater Montreal | South Shore
(514) 476-0730