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What is I.S. 465, and how is it being reviewed?

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I.S. 465 is the Irish Standard that sets out how homes suspected of being damaged by defective concrete blocks are assessed, tested and put into categories. If you apply to the scheme, your engineer and the testing laboratory work to this standard. It shapes what the assessment finds, and so what remediation follows.

This page explains what the current version says, how it came about, and where its review stands. For how the standard fits into an application, see the step-by-step scheme guide.

What is the full name of the standard?

The current version is I.S. 465:2018+A1:2020. Its full title is Assessment, testing and categorisation of damaged buildings incorporating concrete blocks containing certain deleterious materials and Amendment 1:2020.

It was published on 25 September 2020 by the National Standards Authority of Ireland (NSAI). It is © NSAI 2020, and it may not be copied without NSAI permission except as copyright law allows.

What gives it legal standing?

NSAI declared the standard using its power under section 16(3) of the National Standards Authority of Ireland Act, 1996 (No. 28 of 1996), with the consent of the Minister for Business, Enterprise and Innovation. The declaration says:

  1. The instrument may be cited as the Standard Specification (Assessment, testing and categorisation of damaged buildings incorporating concrete blocks containing certain deleterious materials and Amendment 1:2020) Declaration, 2020.
  2. The specification in its Schedule is declared to be the Standard Specification for this purpose. It may be cited as Irish Standard 465:2018+A1:2020, or I.S. 465:2018+A1:2020.
  3. The 2018 Declaration (for the original I.S. 465:2018) is revoked. Any reference in another standard specification to the 2018 instrument, or to I.S. 465:2018, is to be read as a reference to the 2020 instrument and to I.S. 465:2018+A1:2020.

The standard also states that complying with it does not, by itself, give immunity from legal obligations.

What kinds of documents does NSAI publish?

NSAI produces three categories of formal document:

  • I.S. (Irish Standard): a national specification based on the consensus of an expert panel and subject to public consultation. I.S. 465 is one of these.
  • S.R. (Standard Recommendation): a recommendation based on the consensus of an expert panel and subject to public consultation. See S.R. 16 and aggregates for concrete for one example.
  • SWiFT: a rapidly developed recommendatory document based on the consensus of the participants of an NSAI workshop.

Where did I.S. 465 come from?

The standard was developed by the NSAI Concrete Blocks Committee (NSAI/TC 063). It arose from the Report of the Expert Panel on Concrete Blocks, published in June 2017. It was written for those who provide assessment and testing services for dwellings suspected of being affected by defective concrete blocks.

That 2017 report put the damage down mainly to muscovite mica. Research since then points to pyrrhotite and internal sulfate attack. You can read the full history in where the mica narrative came from.

What changed in Amendment 1 (2020)?

The first edition was I.S. 465:2018. Amendment 1 followed a clarification from the Expert Panel:

  • The Department of Housing, Planning and Local Government (DHPLG) reconvened the Expert Panel on concrete blocks in Donegal and Mayo, to clarify Option 1 in Table 5.2 of the panel's report.
  • The panel issued its clarification to the Department in December 2019.
  • Because Table 5.2 was reproduced word for word as Table D.2 in Annex D of the standard, the clarification had to be added to the standard too.
  • A new Annex F contains the text of the clarification.
  • A new note in Clause 8.3 points readers to Annex F.
  • A new footnote in Table D.2 also points readers to Annex F.

In the published document, the amended text is marked with tags.

What does the standard cover?

According to its scope, I.S. 465:

  • sets out a protocol for assessing whether a building has been damaged by concrete blocks containing excessive amounts of certain deleterious materials (aggregate containing free or unbound muscovite mica, or potentially deleterious quantities of pyrite);
  • describes methods for establishing the extent of the problem, and categorises dwellings;
  • describes the scope of any testing required and how the findings are evaluated; and
  • gives the Chartered Engineer guidance on choosing appropriate remedial works.

Its use is limited to concrete block-built dwellings showing signs of distress consistent with damage caused by blocks containing these deleterious materials.

What does it not cover?

The standard is not intended for:

  • the specification, manufacture and compliance testing of new concrete blocks (aggregate concrete masonry units) under I.S. EN 771-3 and its associated test standards, or as a replacement for the guidance in Standard Recommendation S.R. 325; or
  • dwellings that do not show structural damage consistent with defective concrete blocks (see Clause 4 of the standard).

The protocol deals with defective concrete blocks only. It does not rule out other defects in a home that may need attention for other reasons. Your engineer can advise on anything outside the standard.

Which other standards does it rely on?

I.S. 465 refers to these documents in a way that makes some or all of their content part of its requirements. For dated references, only the edition named applies. For undated references, the latest edition (with any amendments) applies.

  • I.S. EN 197-1, Cement – Part 1: Composition, specifications and conformity criteria for common cements
  • I.S. EN 771-3, Specification for masonry units – Part 3: Aggregate concrete masonry units (Dense and lightweight aggregates)
  • I.S. EN 772-1, Methods of test for masonry units – Part 1: Determination of compressive strength
  • I.S. EN 1744-1:2009+A1:2012, Tests for chemical properties of aggregates – Part 1: Chemical analysis
  • I.S. EN 12504-1, Testing concrete in structures – Part 1: Cored specimens – Taking, examining and testing in compression
  • S.R. 325, Recommendations for the design of masonry structures in Ireland to Eurocode 6
  • BS 1881-124:2015, Testing concrete – Part 124: Methods for analysis of hardened concrete

Is I.S. 465 being reviewed?

Yes. NSAI is reviewing and revising I.S. 465, and has said it treats the review as a top priority. The research into pyrrhotite funded by Geological Survey Ireland is intended to inform this review (see where the mica narrative came from).

What happened with the public consultation?

A public consultation on the draft revised I.S. 465 was due to close on 28 May 2025. In the days before, NSAI received requests to extend it from a legal firm representing a large group of homeowners, and from the Department of Housing, Local Government and Heritage.

NSAI agreed to extend the consultation by 6 weeks, to 11 July 2025. It said the reasons given were in keeping with constructive, informed public engagement.

By 28 May 2025, NSAI had received almost 400 comments on the draft. To limit the delay, NSAI said it would begin reviewing the comments already received in parallel with the extended consultation. It described this as a minor departure from its normal process, aimed at delivering the revised standard as quickly as possible without lowering the quality of its work.

This page reflects NSAI's update of 28 May 2025. Your engineer or NSAI can tell you whether a revised standard has since been published. The science timeline also tracks the consultation.

Who is on the committee reviewing it?

The standard is the responsibility of NSAI Technical Committee 63 (TC 63) — Concrete Blocks. These are the voluntary members reviewing and revising I.S. 465:

  • Frank Lee — Chair (NSAI)
  • Ken Murphy — Secretary (NSAI Standards Technical)
  • Pat Carolan — Secretary support team (NSAI Standards Technical)
  • Tim Brosnan — Secretary support team (NSAI Standards Technical)
  • Eddie Comerford — Association of Consulting Engineers of Ireland (ACEI)
  • Simon Dolphin — Department of Housing, Local Government and Heritage (DHLGH)
  • James Duane — NSAI (Sustainability and Built Environment)
  • Seamus Duggan — Master Builders and Contractors Association (MBCA)
  • Mike Eden — Sandberg Materials Consultancy
  • Fiona Fleming — Housing Agency
  • Thomas Holden — Roadstone
  • Dermot McCarty — Roadstone
  • Dr Ambrose McCloskey — Mica Action Group representative (engineer)
  • Damien McKay — Independent Consultant
  • Tom Moore — SLR Consulting / Construction Industry Federation (CIF)
  • Ken Mulkerrins — Kilsaran
  • Eanna Nolan — Cement Manufacturers Ireland (CMI)
  • Aidan O'Connell — Engineers Ireland
  • Paul Quigley — IGSL / Institute of Geologists of Ireland (IGI)
  • Mairtin Ruane — Mayo County Council
  • Colin Scott — Engineers Ireland
  • Conor Taaffe — Homebond
  • John Wickham — Department of Housing, Local Government and Heritage (DHLGH)

The committee includes people from government departments, industry bodies, engineers, geologists and homeowners' groups.

Is there a wider group as well?

Yes. NSAI/TC 73 — Defective Concrete Blocks (DCB) Technical Matters Steering Group supports and informs NSAI's standards work on defective concrete blocks, including I.S. 465. It brings state agencies and government departments into the research and technical direction behind the revision. Its members include representatives from:

  • the NSAI Standards Technical support team
  • the Department of Housing, Local Government and Heritage (chair)
  • the Sustainable Energy Authority of Ireland (SEAI)
  • Geological Survey Ireland (GSI)
  • the Housing Agency
  • chairs of other technical committees, and other state bodies

What does this mean for you?

Your assessment and test results are read against I.S. 465, so it is worth understanding what it covers and what it leaves out. If you are unsure how the standard, or a change to it, affects your home, ask your engineer. You can also contact us.

Sources

  1. Report of the Expert Panel on Concrete Blocks (June 2017) (opens in a new tab)Department of Housing, Local Government and Heritage · gov.ie
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