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Mica and pyrite scandals - could it still happen today?

Experts have said new legislation is needed to ensure building supplies are checked by independent parties.

THOUSANDS OF HOMES in Donegal and Mayo are believed to be affected by defective concrete blocks, which have started to crack and crumble, leaving some families with no other choice but to demolish and rebuild. 

Following a large protest in Dublin’s city centre recently, the government has pledged to do more to help those who are impacted, but campaigners say the State grant scheme will not come close to solving their problems. 

This government’s redress scheme followed a Report of the Expert Panel on Concrete Blocks in 2017 which had expressed concern about regulatory and market surveillance issues.

Though some changes have been implemented to make systems more robust, experts say the government has not done enough to ensure defective blocks do not make it into Irish homes again. 


Micas are a group of minerals that are found in rock, including rock taken from quarries.

In the case of thousands of homes in Donegal and a small number in Mayo, muscovite mica is contained in the building blocks used to construct the houses.

Mica has the ability to absorb and store water and in high quantities results in a disproportionate amount of water in the blocks.

The 2017 expert report noted that estimates suggest that the presence of 1% muscovite mica causes a reduction of the concrete strength by approximately 5% and it has relatively poor bond strength with cement paste.

mica damage

Significantly higher percentages of mica were found in homes in Donegal and Mayo. The presence of this mineral has caused large cracks and fissures to open up in impacted properties.


In 2014 the government set up a Pyrite Remediation Scheme, to assist homeowners whose properties were damaged due to the use of pyrite in the backfill under their foundations.

Using backfill containing pyrite became a common practice in some regions during the property boom. In larger quantities and in the presence of oxygen and water, pyrite, which is a form of iron sulphide, can expand and cause significant structural issues in properties.

In the properties in Mayo that have recently been in the news, pyrite was found in the concrete blocks used to construct the walls, rather than the backfill under the foundations of the houses.

According to technical reports on 17 dwellings provided to the expert panel, the presence of pyrite was consistently reported.

cracks Examples of damage to pyrite-affected homes in Mayo, from the 2017 expert panel report.

“The reports generally conclude that the aggregate used in the manufacture of the concrete blocks tested was unsound and was not suitable for that use because of its potential to cause further deterioration of the blocks,” the expert panel report noted.

Market surveillance of construction products

Under new Brexit arrangements, Dublin City Council was appointed last year as a competent authority for carrying out market surveillance under European Union regulations. 

Its newly-established National Building Control Office (DCC-NBCO) market surveillance unit is now responsible for nationwide market surveillance of construction products. 

It has a team of authorised officers dedicated to carrying out active market surveillance on a nationwide basis, with officers also appointed to each of the 31 local building control authorities, according to the 2021 National Market Surveillance Programme

DCC-NBCO and building control authorities have powers to obtain access to premises to examine, test, or inspect products, request documentation regarding performance and take samples of a product. They can also request that the Minister for Housing prohibit or restrict the use of a product and prosecute offences. 

The 2017 expert panel report highlighted deficiencies in the regulation of construction products. It noted that, while there is a suite of harmonised standards covering most construction products, primary responsibility for demonstrating a product’s compliance rests with manufacturers.

The report further noted that, at the time, enforcement action relating to construction products regulation was generally carried out on a reactive basis, more often “triggered on foot of acting on information received from complaints”.

Four years after the publication of this report, experts in the sector say little has been done to ensure this issue cannot arise again.

Ray Brosnan, managing director of Brosnan Property Solutions, told The Journal that “when it comes to regulations and checks, the entire system is flawed”.

“The onus is rather unfairly placed on the manufacturers to self-certify their own quality control standards and this has become a key part of the whole mica scandal,” he explained.

“Self-certification is something that was introduced in and around the late 90s. This was a type of short-cutting that was green-lit by the government and was running rampant during the boom years, mainly because there were so many homes and apartments being built that it would’ve been practically impossible for regulatory boards to sign-off on every part of the process due to lack of local authority resources and this is still the case.

“For the most part this turns out fine, but unfortunately for the people involved in the mica situation and similarly in the pyrite fiasco, they’ve been let down badly.

In the past, you could have argued that this sort of system is good for the consumer in a way, as it speeds up the building process. But when it goes wrong it can be disastrous, especially for these homeowners.

Brosnan said these issues “could still realistically happen today”.

“It all depends on where the blocks came from, if there is mica present and was it tested properly and found,” he said.

“The vast majority of quarries and manufacturers do implement rigorous and thorough testing policies, but unfortunately something has slipped through the cracks here. It’s due time that the government introduce new legislation to ensure that all building supplies are checked by third, independent parties and are safe.”

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Chartered engineer Aidan O’Connell, speaking to The Journal, explained that while companies themselves might have CE certification, many of the commonly-used products require a declaration of performance (DOP), including concrete blocks.

“The companies produce the DOP themselves, it’s self-certification by them,” he said.

“Up to a few years ago there were suppliers who were supplying building materials that failed the applicable standard – and in my opinion knew that as well.”

He said that while local authorities have a role in the inspection of new build houses, “their role is not to look exclusively at products or materials”.

“My experience with local authority Building Control departments is that they have enough work to be doing with limited staff and resources without visiting quarries and building material plants and factories,” he said. “They wouldn’t have the expertise or the resources to inspect all building material or manufacturers.”

The 2017 expert panel also raised the issue of resourcing and expertise in local authorities. 

It stated:

During the period under consideration, building control authorities did not have the technical resources in-house to test construction products which may have been non-compliant with the requirements of the Construction Products Directive. In this regard, all enforcement activity was (and remains the same today) performed within existing local authority budgets and remained subject to national restrictions on Government spending following the downturn in the economy in 2008.

While the panel stated it did not consider it was reasonable to expect that building control authorities could have prevented this problem from occurring, it advocated for “more meaningful on-site inspections and enforcement”.

It also recommended that market surveillance authorities be sufficiently resourced with dedicated units, which would have expertise in the quarrying sector to provide effective enforcement nationwide.

The 2021 market surveillance programme acknowledges that neither the National Building Control Office, nor building control authorities have the technical resources in-house to test construction products which may be non-compliant with regulations.

“Typically, the testing and evaluation of construction products, where considered necessary, will be outsourced to accredited bodies providing such services,” the document states.

It also notes that all enforcement activity “will have to be performed within existing budgets”.

Dublin City Council did not respond to requests for information about its enforcement powers or the number of inspections it has carried out over the last 12 months. The Department of Housing told The Journal that it provided a budget of €500,000 in 2020 to support the development of the DCC-NBCO’s market surveillance unit.

It said €147,000 of that budget was spent, “as the project was at the early development set-up phase”.

This year a budget allocation of €565,000 was provided by the department for the development and resourcing of the unit.

The department said a market surveillance campaign led by DCC-NBCO, which has recently commenced, involves risk assessments of selected quarrying and pit operations, follow-up inspections and testing as appropriate to ensure compliance with regulations.

Aidan O’Connell said he is not aware of any anonymous reporting system for someone who believes there may be a problem with a particular supplier.

“Ultimately that would be determined in court and I have cases in court at the moment, but that’s very much after the fact. There are suppliers who have supplied building materials in contravention of standards well after new standards were brought in to protect the public,” he said.

When asked whether he believes there may be companies in Ireland currently supplying sub-standard concrete products that could lead to similar structural issues in homes years down the line, he replied: “Absolutely, 100%.”

In response to a query from The Journal, The National Standards Authority of Ireland (NSAI), which sets the standards for construction products, said that in light of the pyrite and mica issues, Ireland introduced enhanced standards which offer further guidance on the use of aggregates in construction products. 

The NSAI said it is a requirement for manufacturers to have a petrographic test, conducted by an accredited professional, and a geologist’s report as part of their initial application process for certification.  The authority said its audits on block manufacturers also look to see that this testing is in place.

The standards recommendations do not specify who carries out testing and the NSAI said it is often outsourced to external labs as manufacturers do not have the approved facilities. 

There is no requirement for regular testing by manufacturers throughout the year to ensure products continue to meet the standard.

Certificates of compliance

In 2015, following a review of legislation, the government decided to relax building regulations for single property developments. Prior to this, a statutory certificate of compliance on completion was to be signed by a registered construction professional – an ‘assigned certifier’ – who deemed the property to be structurally sound, of good quality and safe.

It was decided following the review that owners of new single dwellings on a single development or those building a domestic extension could opt out of the requirement to obtain certificates of compliance. 

This is still the case today, despite concerns raised by the mica expert group which described this relaxation of regulations as “a retrograde step”.

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Although this opt-out was not part of regulations at the time many of the impacted homes were built, the report warned that a lack of professional supervision of works “could contribute to repeat building failures” such as those seen in Donegal and Mayo and that these should be amended.

Chartered engineer Aidan O’Connell said an assigned certifier would seek copies of all certificates for materials used to build the property including concrete blocks, structural steel, stone infill beneath floor slabs, insulation and structural timber.

“For people who build a once-off house, they may own a site, maybe they were given a site by their father or another family member, and they are on a tight budget to build their house,” he said.

“I would find that an awful lot of people, 95% of people, in my opinion, would seek to build the biggest house they possibly can within a very tight budget and therefore if they can save money by opting out of the cost of having an assigned certifier, they will do that.

“The cost could be from 3-5% of the build cost of the house because there’s a huge amount of time involved in making sure every element has been done 100% to standard. There is a higher degree of supervision and review in this process, rather than the standard built house.”

The Department of Housing said this opt-out was introduced due to “the perceived high costs” of the procedures for owners of these properties.

It said that whole owners can forego statutory certification, the requirements of the building regulations still apply. 

“The primary responsibility for compliance with the building regulations rests with the designers, builders and owners of buildings,” the department said.

It pointed out that it has published an information note for owners who opt out of statutory certification explaining the building control system and providing advice on statutory obligations that rest with owners who opt out. 

The department acknowledged that it has not, as recommended by the expert panel report, carried out a review of this opt-out provision. 

It added: “However, National Building Control Office (NBCO), continue to monitor the uptake and use of S.I. No. 365 of 2015 and reviews of the building control regulations are undertaken by the department, as necessary, as part of the ongoing Building Control Reform Agenda.”

This work is co-funded by Journal Media and a grant programme from the European Parliament. Any opinions or conclusions expressed in this work is the author’s own. The European Parliament has no involvement in nor responsibility for the editorial content published by the project. For more information, see here

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