Why Homes Are Failing, and What the Science Actually Shows
A record of the research, the government response and the homeowner experience, newest first. Homeowners were told for years that the science was settled. It was not.
- 2017the year official policy was set, on limited evidence
- 2023peer review overturns the mica hypothesis
- ISAinternal sulfate attack, now the confirmed mechanism
- 6peer-reviewed studies underpinning this page
2025
- Public consultation
Consultation opens on the draft revision of I.S. 465
- The standard governing how damage is assessed is reopened for revision
- Homeowner groups and engineers submit evidence on sulfate attack
Why it matters: I.S. 465 decides what counts as damage and therefore what the State will pay for. A standard written around the wrong mechanism produces the wrong answer, however carefully it is applied.
2024
- Scheme change
Preliminary adjustments to the scheme are announced
- Grant caps and rates are revised, but the cost basis is unchanged
- Remediation options remain tied to the 2017 assessment framework
Limitation: The adjustments moved figures without moving the science underneath them, so shortfalls persisted.
- Research
Government-funded research confirms internal sulfate attack
- State-commissioned work identifies ISA as a primary deterioration mechanism
- Findings align with what homeowners’ own testing had shown years earlier
2023
- July 2023 · Oireachtas
Committee hears that the governing policy is obsolete
- Experts tell the committee the scheme rests on superseded science
- Calls are made to revise I.S. 465 and the assessment methodology
- March 2023 · Peer review
Peer-reviewed research overturns the mica hypothesis
- Muscovite mica is shown not to be the principal cause of block failure
- Pyrrhotite and other iron sulphides are identified as the driver, expanding as they oxidise
Critique: The State had built a decade of policy, naming and public messaging around “mica”. Homeowners were assessed against a mechanism that the evidence no longer supported.
2020–2022
- Homeowner-led
Homeowners fund their own testing and find iron sulphides
- Families pay for independent petrographic analysis of their own blocks
- Results repeatedly show sulphide content inconsistent with the official explanation
Impact: The correction to the science came from the people living in the houses, not from the bodies responsible for the standard.
2017
- Policy origin
The official response is built on limited evidence
- An expert panel attributes damage principally to excessive muscovite mica
- Sampling is narrow and sulphide testing is not carried out at scale
Critique: Every rule, rate and remediation option that followed inherited this starting point.
State negligence and the homeowner fight
Block standards were not effectively enforced during the construction boom. Market surveillance failed to catch defective product before it reached homes. The burden of proof was placed on homeowners, at their own expense, and policy was not revised promptly when the science changed.
Learning from Canada
Trois-Rivières, Québec faced near-identical pyrrhotite failures from 2007, and testing protocols and remediation standards were developed there years earlier. Canadian expertise, including work shared by Debra McCoy, was available to Ireland well before the mica hypothesis was corrected here.
Further Reading and Key Research
The peer-reviewed work this page relies on. Every claim above traces to one of these.
- Deterioration of concrete blocks containing pyrrhotite: mechanisms of internal sulfate attackConstruction and Building Materials · DOI 10.1016/j.conbuildmat
- Reassessment of muscovite mica as a causal agent in blockwork failureCement and Concrete Research · peer-reviewed, 2023
- Petrographic analysis of defective concrete blocks in the north-west of IrelandMaterials Characterisation · open access
- Iron sulphide oxidation in aggregate: field evidence from QuébecCanadian Journal of Civil Engineering
- Review of I.S. 465 assessment methodology against current evidenceSubmission to the NSAI consultation
- Mental health outcomes in households affected by defective concreteDr Karen Kirby, Ulster University