How RAAC Was Promoted Despite the Warnings: A Letter to the Prime Minister

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Rt Hon Sir Keir Starmer MP

Prime Minister of the United Kingdom
10 Downing Street
London, SW1A 2AA

Cc: Rt Hon Angela Rayner MP
Secretary of State for Housing, Communities and Local Government
2 Marsham Street
London, SW1P 4DF

OPEN LETTER:  Urgent Request for a Public Inquiry into the Use of RAAC in Public Buildings and Housing

[This letter has been emailed to the PM, Secretary of State and Ministers. Printed copies are scheduled for hand-delivery to 10 Downing Street on Tuesday, 10th June at 2:00 PM.]

Dear Prime Minister and Secretary of State,

I am writing to urge the immediate establishment of a statutory Public Inquiry into the historic approval, promotion, and widespread use of Reinforced Autoclaved Aerated Concrete (RAAC) in public housing and infrastructure across the United Kingdom. Mounting evidence indicates that the adoption of RAAC was not simply a matter of engineering misjudgment, but rather a profound failure of public oversight, transparency, and accountability.

To this day, thousands of UK residents remain displaced, at risk, or caught in limbo due to structural failures associated with RAAC. However, the roots of this crisis run deeper than the material itself. The public deserves answers to how this dangerous substance came to be so widely used despite early warnings. Notably:

• Costain Group conducted research for the British Research Establishment (BRE), which directly influenced the approval of RAAC for use in system-built housing.
• Richard Costain facilitated visits for UK politicians to Sweden to promote RAAC technology and partnered with the Edinburgh Research Unit (ERU) to develop the first Siporex towers in Scotland.
• The ERU later created an automated building design system directing councils and the Scottish Special Housing Association (SSHA) to use specific pre-approved construction systems—such as Skarne, Jespersen, and Bison—all of which incorporated RAAC.
• During this period, Albert Costain MP, a former Costain Group director and shareholder, promoted system-built housing in Parliament—raising serious questions about conflicts of interest and influence over public procurement.
• Following the Ronan Point disaster, a safety review into system-built housing was mandated—but it was conducted by the BRE, an institution that had previously promoted these systems. Alarmingly, Scottish housing was excluded from that review, allowing structural risks tied to Siporex and RAAC to go unexamined.

Further troubling evidence includes:

• In 1987, Edinburgh Council acknowledged RAAC-related roof risks by commissioning steel reinforcement over asbestos roofs at 159–163 Crewe Road North (Edinburgh Evening News, 22 June 1987). Later council claims that these works had no relation to RAAC have proven misleading.
• A 1989 article in The Glasgow Observer revealed that homes in Livingston saw their value slashed by two-thirds after structural surveys condemned RAAC roofs. Although Siporex-related defects had already emerged in Basildon, Mr Gordon Davies, technical director of Livingston Development Corporation, assured the public that similar risks were unlikely in Livingston. This proved untrue, yet homes continued to be sold to unsuspecting buyers.
• A 1967 article in the Reading Evening Post described Siporex as a remarkable new material that “floats”—even comparing it to cheese that could be “sawn” or “nailed.” In reality, RAAC is dangerously water-sensitive and disintegrates when wet. Such promotional misinformation helped normalize the use of an inherently unstable product.
• A 2005 City of Edinburgh Council report confirmed the use of Siporex in non-traditional housing, based on a structural survey by Curtins Consulting—who now manufacture the very steel support systems being installed in Dundee to address RAAC risks. This suggests long-standing awareness and potential conflicts of interest.
• In 2017, the Lanarkshire Valuation Joint Board classified Siporex as RAAC in official guidance, identifying its widespread use in Cumbernauld during the 1960s and 70s. This contradicts subsequent denials by North and South Lanarkshire Councils that they knew of its presence or dangers.
• A 1989 Evening Chronicle article shows Newcastle City Council had already identified serious RAAC defects in homes with "Siporex roofs" by that time—further confirming that the risks were known and documented decades ago.
• As early as 1959, Siporex was marketed in Scotland as a revolutionary material, claimed to be “non-combustible” and comparable to stone. Crucial information about its moisture vulnerability and long-term deterioration was conveniently omitted.

Taken together, these failures—technical, regulatory, and ethical—have left a trail of destruction: structural instability, financial devastation, and psychological trauma for countless families. Piecemeal responses and deflections of responsibility are no longer acceptable.

We therefore call for a full statutory Public Inquiry with powers to:

1. Investigate the original approval, research, and promotion of RAAC—including the roles of BRE, Costain Group, ERU, and relevant government departments;
2. Examine the influence of corporate lobbying and potential conflicts of interest in housing policy and procurement;
3. Review the Ronan Point safety investigations and the exclusion of Scottish properties from scrutiny;
4. Assess the human, financial, and psychological toll on affected residents and the adequacy of current remediation and compensation;
5. Recommend structural reforms to prevent such regulatory failures from recurring.

This matter demands urgent and transparent action. Public confidence in the safety of our homes and in government decision-making cannot be restored without full disclosure, accountability, and justice.

I would welcome an opportunity to meet with you both in person to present the evidence we have collated and to discuss the urgent need for a Public Inquiry. I would also be keen to contribute further evidence to any inquiry process and to support its formation in any way necessary.

Yours sincerely

Wilson Chowdhry

Chaorman UK RAAC Campaign Group