Frequently Asked Questions about Pyrite Testing and Pyrite Damage

Pyrite Damage in Ireland.

The damage that pyrite backfill can cause is an expensive defect to remedy and stressful to the property owner. The percentage or concentration of pyrite in the backfill and the age of the property will determine the extent of the expansion that would have taken place under the concrete floors. It can take up to ten years for the first signs of pyrite damage to show. Studies have shown that pyrite in backfill can take upwards of 30-40 years to swell where no more expansion can be expected and backfill will become stable.

Removing the contaminated pyrite backfill is an expensive operation and in most cases will involve supporting the existing first floor, roof structure, removing the ground floor concrete floor, partition walls, replacement and removal of all plumbing fixtures, heating and electrical systems in the affected area, before the contaminated pyrite backfill can be removed.

Cracked Walls and Floors

Because of the wide spread use of contaminated backfill, properties that have no pyrite in their backfill or still been suspected of having a potential pyrite problem, as settlement or drying cracks are very common in houses and in some cases these cracks are been incorrectly diagnosed as being a pyrite issue. The effects of pyrite expansion can, as we know take up to forty years to stabilise.

Frequently Asked Questions about Pyrite in Houses.

If I suspect pyrite in my house, what should I look for?

In most types of house construction, backfill is compacted over the soil and then the concrete floor slabs is poured over the backfill. The presence of pyrite in the backfill will cause the concrete floor slab to lift and crack over the swelling backfill. The presence of Pyrite mixed in with this gravel can, when certain conditions are present, cause part or the entire slab to lift several millimeters, causing cracks in the slab. This results in cracks in the concrete floor slab. The form of the crack is the clearest indicator as to whether this crack is caused by swelling due to the presence of Pyrite. Cracks caused by Pyrite are generally in the form of an X, a cross or a star, almost as if a tree was trying to push up through the concrete. The interior partition wall may also lift resulting in the sticking of interior and exterior doors which will catch on the rising floors. You may also find crystalised salt, or needle-like white crystals may visible in the cracked concrete floor. There is generally the appearance of a fine white power coming from the cracks as well. These types of cracks take several years to appear; generally a dozen years or so after the slab was poured.

Depending on the depth of the pyrite infected back fill, various types of cracks can be seen in the floor and walls, including rising floors in the corners of rooms or the creation of a star type crack towards the centre of the floor.

It Appears THAT I HAVE PYRITE in my house. WHAT DO I DO NOW?

The only way to know for certain is to carry out a test.  If you are selling your property, you may have to get test done to satisfy the buyer that there is no pyrite problem

IF THE Paths and driveway around my house contain pyrite. CAN THIS BE effect my house FOUNDATIONS?

No. It most cases this will not effect the foundations. Only the Pyrite backfill that is under concrete floor in the house will damage the foundations. The same generally applies to the reinforced concrete piers holding up the property as they are supported on undisturbed soil with no pyrite underneath.

Does my insurance policy cover for pyrite damage?

A home owners insurance policy would not normally cover for defects caused by pyrite. A building guarantee or insurance bond may cover. It is important to read these policies in full. Unfortunately home owners are finding that their insurance cover is not as comprehensive as they first thought or in some cases the policy is almost non-existent.

IS THERE A Government SUBSIDY TO HELP HOMEOWNERS who have pyrite damaged houses?

There is currently no government initiative to assist or subsidise home owners to repair their pyrite damaged homes

Does the chemical reactions in Pyrite cause a health issue?

No, other then the financial and other stresses it leads too. Medical opinion suggests that the quantities of sulfuric acid are too small to cause health problems. However it is possible that the radon barrier maybe compromised by the swelling backfill leading to ingress of radon gas into the dwelling.

Which counties are you likely to find pyrite issues?

Dublin, Louth, Meath, Kildare, Westhmeath, Wicklow and Offaly, other counties are also effected to a lesser extent.


The house builder is not obliged to undertake soil tests or test each consignment of gravel backfill that is delivered to his building site. However, the house builder responsible for the materials they use to build each home under Part D of the Building Regulations.

Is my concrete floor slab going to crumble and swell over time?

Yes, the pyrite will result in the concrete floor slab which is resting on the backfill crumbling over time. When the sulfuric acid in the backfill reacts with the concrete floor slab, the underside of the concrete floor slab will swell from sulphation and begins to breakdown and crumble.

Is the swelling backfill going to spread out and damage my foundations and rising walls?

When the contaminated pyrite backfill expands, the swelling usually pushes upwards from the centre and corners of the concrete floor slab. If the depth of the backfill under the floor slab is significant and the percentage of pyrite contamination in the backfill is on the higher side, the  foundations and rising walls may not be strong enough to prevent horizontal expansion, thus resulting in foundation spread. This swelling will result in cracks in the foundations and rising walls around the property. In most cases the the initial swelling is forced upwards along the path of least resistance.

Should I take my builder or insurance company to court?

It is advisable to seek legal advice before thinking about taking legal action. In a number of high profile cases which have already gone to the courts it would appear that the courts are taking the side of home owners if contaminated pyrite backfill has been found under their floor slabs. Unfortunately as we can see from recent cases, that the Homebond insurance policy and most builders are not in a financial position to carry out these repairs even if you were to win your case.

Are older properties likely to be affected?

The majority of properties affected have been built during the celtic tiger years. However some older properties are also affected and the defect was not correctly diagnosed.

I built a rear extension on to my property in the last fifteen years, is my extension likely to be affected?

There are estimated to be a greater number of extensions that have been added to older properties then there are new houses built using contaminated pyrite backfill. As in new houses the same defects will become visible over time. Any pyrite backfill used in the new extension will not effect the main structure of the original house

How quickly will it take to see the effect of pyrite?.

The speed of reaction will depend on the depth of the backfill, the extent of the pyrite within the backfill and the amount of oxygen and moisture available to allow the reaction to take place. Studies in Canada show that the expansion in backfill may take in the region of forty years to stablise.

What if I have a number of cracks in my concrete floor, do I have a pyrite problem?

Most concrete floor slabs will develop drying cracks within the first year after construction. These cracks are normal when concrete floors dry out too quickly. When the concrete floor dries, it will shrink resulting in cracks. In most cases the cracks are not caused by swelling due to contaminated pyrite. The presence of significant cracks in the floors or walls of houses is more likely to indicate the presence of other foundation or structural problems, not associated with pyrite. The only way to know is to have the cracks  surveyed.

WHO PAYs FOR THE pyrite TESTing if a house is for sale?

The buyer would normally include in the contract documents that the vendor obtain a pyrite test to determine if there is a current or future risk of swelling under the concrete floor slab in the house or new extension. The vendor is not under any legal requirement to have this test carried out, however if he does not get the test carried out he is likely to lose the sale of the property. This is a straighforward case of negotiation between the buyer and the vendor.

What are the short term solutions to slow down the rate of pyrite expansion?

  • Prevent the ingress of moisture from cracks in floors and walls
  • Make sure that there is proper drainage away from the property.

These solutions are short term and their objective is to slow down the rate of pyrite expansion under the concrete floor.

What are the longterm solution to remedy a pyrite problem?

  • The only longterm solution is an expensive solution which involves substantial building works as follows.
  • Break and remove the concrete slab floor
  • Remove the backfill and any contaminated subsoil
  • Replace the backfill with material complainant with Part D of the Building Regulations.
  • Pour a new concrete slab.
  • Existing services, partition walls and first floors would also need to be replaced and supported during this re-instatement.
  • This work should be undertaken by competent building contractors.

Are quarries now testing for the presence of contaminants in backfill material?

Yes, but always source your backfill directly from quarry whose backfill material can be certified as pyrite free

Do qualified contractors exist who specialise in the repair of pyrite damaged homes?

No, we are currently establishing a database of contractors who can carry out pyrite repairs as per the system that operates in Canada.  For example in Canada were there are estimated to be between 300,000 to 500,000 properties with pyrite problems. There is no accurate figure available as to the number of  subsidies paid out by local authorities in Canada to assist home owners carry out repairs to their properties, however the estimated cost of these repairs are less then half of the estimated cost to have pyrite damaged houses repaired in Ireland. We would hope by following the Canadian system and complying with proper building regulation standards in Ireland that costs can be reduced to a similar level as in Canada.

My neighbours house has a confirmed case of pyrite, does this mean that I have pyrite to?

There is a likelihood that there maybe pyrite under your floor, however, only a test for pyrite will confirm it’s existence.

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