Pyrite & Mica FAQ

Deleterious materials is a blanket term for materials which detrimentally effect the strength, workability, and long-term performance of blocks.

Pyrite and Mica are two forms of naturally occurring minerals found in stone. When either are present over a certain level both cause the block to degenerate over time. Pyrite is an iron sulphide, when in abundance this reacts with moisture and oxygen in the air, producing sulfuric acid causing the block to rot. Mica acts like a sponge, the more that is present in a block, the more moisture the block holds. When this moisture freezes within the block it causes the block to expand, this prolonged freeze thaw action causes the block to weaken and crumble.

The National Standards Authority of Ireland (NSAI) established a Technical Committee to develop a standardised protocol in response to the Pyrite & Mica crisis. This standard is the ‘I.S. 465:2018 it:

  • Establishes a protocol for assessing and determining whether a building has been damaged by concrete blocks containing certain excessive amounts of deleterious materials (free or unbound muscovite mica or aggregate with potentially deleterious quantities of pyrite).
  • Describes methods for establishing the extent of the problem
  • Describes the scope of any testing required
  • Categorises buildings in accordance with the standard, providing competent persons with guidance on the appropriate measures to be taken

Defective Concrete Blocks Grant Scheme

Owners of dwellings located in Donegal or Mayo which are damaged due to the use of defective blocks, this is being extended to include Clare and Limerick. The dwelling must be

  1. The individual’s principal private residence where they reside
  2. a rented dwelling with a Residential Tenancies Board (RTB) registered tenancy on November 1st, 2021, subject to a maximum of one rental property per household

The dwelling must

  1. be a house, apartment, maisonette, or duplex
  2. locate in the administrative aera or a relevant authority
  3. construction completed prior to the 31st of January 2020
  4. constructed using defective blocks and damaged as a result
  5. occupied as a principal residence or a property registered with the RTB on the 1st of November 2021
  1. Holiday Homes
  2. Vacant Residential Properties
  3. A building or part of a building or office that is not attached to a dwelling
  4. A yard, garden, or other land appurtenant to a dwelling
  5. A building other that a building comprising apartments, duplexes or maisonettes that provide muilti-occupancy accommodation
  6. Dwellings owned by a Public Body
  7. Commercial/retail premises

You are eligible if the dwelling must be an individual’s principle private residence and the individual must intend in good faith to reside in the dwelling as their principal private residence on completion of qualifying works.

Generally, you will not be eligible for a grant, however in certain limited circumstances a local authority may consider an application in good faith on the honest belief that they either did not know or could not have known that defective concrete blocks were used in construction.

A dwelling may be deemed as the individual’s principal private residence where the dwelling previously has been but ceased to be such by virtue of the damage to the dwelling arising out of, or in connection with, the use of defective concrete blocks in its construction.

As a pre-condition to the final payment a Certificate of Remediation will be required signed by your contactor and a competent engineer.

Generally, no, however any costs associated with essential immediate repair works related to the structural stability of any part of an affected home, which are recommended on foot of an engineer’s recommendation as part of the ‘Building Condition Assessment’ process, we be an allowable cost subject to a maximum expenditure cap of €5,000.00.

Under proposed enhancements to the scheme the Housing Agency will recommend a remedial option that represents the appropriate works to remediate the dwelling.

No. A building or part of a building or out office that is not attached to a dwelling is excluded from this grant scheme. If the garage is contained within the footprint of the building and was constructed as part of the original construction is covered by the grant scheme.

Yes, there is grant assistance available from the Sustainable Energy Authority of Ireland (SEAI for DCB (Defective Concrete Block) homeowners to cover the costs of energy upgrades which should reduce energy costs going forward and reduce the financial burden on families over time. Grants are available to DCB homeowners under the same criteria as all other homeowners who are not affected with DCB.

For a more comprehensive explanation of the Defective Concrete Blocks Grant Scheme please visit

  1. Location
  • Donegal
  • Northwest Mayo
  • Sligo
  • Clare
  • Limerick
  • Tipperary
  • Meath
  • Wexford
  • Carlow
  • North Kerry

2. Structural

Pyrite & Mica defects

  • Web Cracking, Pattern Cracking
Web Cracking
Pattern Cracking
  • Vertical Cracking 100mm – 200mm Cracking from corners
Vertical Crack 100mm - 200mm from corner
  • Horizontal Cracks (possibly attributable to day joint blockwork)
Horizontal cracks
  • Disintegrated blocks also known as “Weetabix block”
Disintegrated blocks, leaving void in external leaf
  • Outward bowing of external leaf
Outward bowing in external leaf
  • Displacement at window/door reveals
Displacement at door-window reveals
  • Blown render (Missing pieces of plaster)
Render blown or missing

*Please note that cracking is inevitable with every structure, settlement cracks with appear gradually over the years and stay relatively unchanged. Cracks resulting from Pyrite and Mica vary from minor in appearance “small lines” to major “wide and jagged”, the indicator is the speed at which the cracks develop/deteriorate. Visible deterioration with Pyrite & Mica cracks is evident within a few months. One common similarity we have discovered is the frequency with which people are painting their houses and cracks that have re-appeared after filling and painting.

3. Timeframe

If the structure was built between the 1990s and the late 2000s especially in the mid-range of that time, it is likely to be affected by Pyrite or Mica
If your structure fits any criteria in more than two categories, we advise to get your property tested.

  1. Who – Builder/Contractor

Who constructed the property?

  1. What – Materials

What quarry did the blocks come from

  1. When – Year

When was construction competed?

  1. Where – Location

Is the property located in Donegal, Mayo, Clare, Limerick, or other potentially affected homes.

Certificate of Compliance

The Building Control Authority issue Certificate of Compliance and Completions, and this is issued on receipt of all necessary ancillary certificates provided and signed by assigned certifier (architect or engineer).  This information can be looked up on the National Building Control and Market Surveillance Office website (, unfortunately this is only active since 2014 and information on structures completed prior to 2014 will not be on this database.

For structures completed prior to 2014 the buyer should be looking for the Engineers “sign-off” on an “Opinion on Compliance”. Typically, this information is kept with the deeds or the owner’s solicitor, however as there was no strict regulation on this documentation prior to 2014 if it was not requested when the property was originally completed it may never have been issued and there is no public record to access this information.

If the seller has had their property tested, they should be able to provide an ‘Engineers Report’ or a Pyrite/Mica Free Declaration.  The crucial details on these documents regarding Pyrite and Mica are:

  • Pyrite: Total sulphur level for Pyrite 0.1% or less
  • Mica: There no acceptable allowable limit for Mica it is still very much a grey aera currently we are cautiously advising based on international information anything below 5% of Mica is acceptable.
  • Pyrrhotite: There is a body of evidence emerging that Pyrrhotite may be the root cause / primary cause of deterioration of blockwork to homes in Donegal.

Support for Sellers

If you are considering or are in the process of selling your property, we would recommend one of the following:

Simplified Petrography Test

A Simplified Petrography Test examines concrete block samples extracted from your property and are classified by Suite A examination to determine if the samples are displaying levels susceptibility to deterioration due to the presence of potentially problematic deleterious lithologies/minerals. Samples are classified under Negligible, Low/Medium, High or Critical risk.  Although this is the most time effective way of establishing the status of your house it only proves to be cost-effective if a Negligible result is returned as further testing would be required in the event of a Low/Medium, High or Critical risk result to avail of the redress scheme.

Pyrite and Mica Testing in Accordance with I.S. 465 (Defective Block Scheme) 

 This route is both more expensive and time-consuming, however in the event of our house having a medium or high result you will have all the scientific evidence and documentation required to avail of the redress scheme.  This is a huge bonus for potential buyers as the first step as been taken and they will be further along the process.

Application Process

Stage 1 – Confirmation of Eligibility

The Homeowner applies to the Local Authority providing a completed Engineers Report including completed testing of block samples in accordance with IS 465 as evidence of damage to dwelling. The Local Authority confirms eligibility to proceed to stage 2, subject to the terms of the scheme.

NOTE – Core samples are required to be taken from the exterior block work above and below ground and from the interior block work. The core samples are sent for Laboratory testing to confirm the levels of Mica / Pyrite.

Stage 2 – Grant Approval

Before works commence, the homeowner applies for grant approval, providing estimated costs to remediate the dwelling.

Local Authority confirms the maximum, approved grant amount, subject to the terms of the scheme.  

NOTE – It is a requirement that the Engineer who prepared and issued the initial Engineers Report, prepares, and issues the most appropriate remediation works.

Stage 3 – Payment of Grant Payment of the approved grant happens on phased based via interim drawdowns based on certification of progress of works. Local Authority pays grant to homeowner, subject to the terms of the scheme.

NOTE – An Engineers Final Certification is required to confirm the works were completed in accordance with the approved remediation works. It is advisable that the Engineer who prepared and issued the initial Engineers Report, and proposed Remediation works, prepares, and issues the Final Certification, an Assigned Certifier type person.

What help will TA Group provide to you the Homeowner

TA Group as complete service provider will provide a One Stop Service to all homeowners.

Stage 1 – TA Group will complete the Engineers Report, required by the Local Authority, including all on site sampling and laboratory testing of site samples.

Assist the Homeowner in completing the application to the Local Authority

Stage 2 – TA Group will provide a detailed remediation design, planning and cost estimated to you the homeowner for grant approval by the Local Authority.

Stage 3 – TA Group will complete the construction remediation works and certify the works for you the homeowner for payment of grant approved.

Why TA Group?

We are a team of Architects, Engineers, Quantity Surveyors and Project Managers. We specialise in Building Compliance, in every project we undertake we provide building solutions. Expanding into Pyrite and Mica was a natural progression when this crisis emerged. Initially like all professionals dealing with this subject matter our knowledge was limited, however after months of independent research and testing TA Group have become one of the most prominent engineering consultants in Ireland.

We are the only engineering company that is operating in both Mayo and Donegal and will be expanding operations into Clare, Limerick, and all affected counties when the scheme is extended. Due to the unique geographical range and volume of clients we have dealt with, we were requested to provide data to the Expert Working Group Panel that took place in February 2022. We have also had the honour of being asked to speak on behalf of the homeowners in front of the Oireachtas in June 2022 on behalf of the Homeowners.

We have tested blocks from several quarries around Mayo and Donegal allowing us to advise our clients based on 100% fact rather than opinion as they progress through this system. At TA Group we provide all construction services under one roof. We have a wide range of highly skilled and educated staff, including Architects, Engineers, Quantity Surveyors and Administrative Staff. We provide services within the building and civil engineering sector throughout Ireland for Local Authorities, Semi-State Companies and Private Clients.

Get in touch today to discuss the best options for you with one of our highly trained and experienced experts.

Get in Touch Now to find out how TA Group can Support your Pyrite and Mica Engineering and Testing Needs