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.

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

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