Reinforced Autoclaved Aerated Concrete advice

There have been a number of reports in the news about a particular form of construction: Reinforced Autoclaved Aerated Concrete (RAAC). This is because a concern has emerged around a potential risk of sudden collapse in schools and other buildings where this material is used.

Below you’ll find advice about RAAC and what building owners and responsible persons need to do.

What is RAAC?

RAAC is a building material which has been used primarily in schools and hospitals but has been found in a wide range of buildings. It was most commonly used for roof construction (notably flat roofs) but can also be found in floors and walls. It is white or grey in colour with a ‘bubbly’ appearance. It was widely used in construction from the mid-1950s to the mid-1980s (although it was used in some cases in the 1990s). It had an expected lifespan of around 30 years.

What is the concern?

RAAC is present in some buildings despite it being well over its expected lifespan. Roofs built with RAAC have been known to collapse suddenly with little or no warning and have caused injury. It has also recently been widely reported that several hospitals are now having to use temporary steel props to hold up RAAC roofs to reduce the risk of collapse. This report from CROSS (Collaborative Reporting for Safer Structures) provides details of the failure of RAAC planks in schools.

What do building owners and responsible persons need to do?

Due to the limited durability and known issues of RAAC, it is essential that building owners take steps to confirm the safety on any RAAC in their premises. The Local Government Association has published steps to confirm the safety of RAAC construction to assist with this.

For those responsible for fire safety in a building it is important that there is a full understanding of the construction of the building, not only to understand the structural integrity, but also how this might impact the fire safety precautions.

If RAAC is suspected to be present, then the building owners should undertake a structural survey to provide confirmation. This survey should be carried out by a competent person (such as a Chartered structural engineer or a Chartered civil engineer with relevant experience in RAAC) and this survey should then be used to inform the premises fire risk assessment.

Fire safety advice

How the construction of the building reacts and behaves in a fire is considered to fall within the scope of the Regulatory Reform (Fire Safety) Order 2005. This is because in this instance, for RAAC construction, a fire could potentially promote early structural failure.

If RAAC is confirmed to be present, then the Responsible Person needs to consider whether the fire risk assessment for the premises should be reviewed and revised. The presence of RAAC could result in areas of a building not being able to be used due to the potential performance in a fire, regardless of if it has been deemed safe structurally for normal use. The location of RAAC and how these areas relate to the fire strategy for the building needs careful consideration by the Responsible Person. Subsequent construction works in relation to these areas could also impact the fire risk assessment.

A review of the fire risk assessment should ensure that an appropriate standard of fire safety is maintained and should give due consideration to the following areas.

  • Where the means of escape is affected by any mitigation measures taken in relation to RAAC, those responsible for the fire safety in the building must ensure they remain suitable for the number of persons and occupancy types that are expected to use them. This should include considering their protection particularly in relation to surrounding structures, and where escape routes or final exits are no longer usable that suitable means of escape is still available. Changes in layout could result in the creation of single direction escape, increased distances to an exit and the need to revise exit signage.
  • Where parts of a building can no longer be used, it may be necessary to change how other parts of the building are used to account for lost space. The fire risk assessment will need to consider how this could impact both means of escape and capacity, including a review of the disabled evacuation strategy and also if any change of use impacts the level of fire risk. For some sites new temporary accommodation may need to be created. This is likely to need consultation with a Building Control Body.
  • The impact of moving people out of a building may create lone worker situations which need to be considered. Any buildings used to accommodate displaced people would also need to be considered in terms of potential impact on their fire risk assessment due to increased numbers of occupants, and potential change of risk in these areas etc.
  • It is important that any changes are clearly communicated, and management provisions and training are adjusted accordingly. Where the emergency plan has been changed, we strongly recommend that fire drills are carried out as a matter of urgency to familiarise occupants with the changes.
  • Where specific emergency procedures are implemented to support structural safety concerns, it should be ensured that they do not conflict with the existing procedures in the event of a fire to the extent that they could cause confusion and place people at risk.

As well as the protective measures above, it is also critical the fire risk assessment identifies proper preventative measures and that the Responsible Person implements them - as a fire in a building identified with RAAC could potentially promote collapse. Where a building has been vacated then there remains a need to minimise risk of arson or deliberate fires so sites should be adequately secured.

In terms of schools, as of 31 August 2023 the advice for schools as published by the Government is;

“Guidance advises responsible bodies and settings on how to identify RAAC and what they should do if it is confirmed, including vacating and restricting access to the spaces with confirmed RAAC. Spaces should remain out of use until appropriate mitigations are in place”. The DfE website offers further specific guidance.

Regardless of whether the school is continuing to operate with mitigation measures in place or supporting other schools by accommodating their staff or pupils; it is recommended that fire drills are undertaken as soon as possible to identify any potential unexpected consequences resulting from changes in the building layout and occupancy which may need to be addressed.

Notifying LFB

If RAAC has been identified within your building then we request you notify us so that we can update our records, particularly in the event that a fire or other incident occurs in the building so that we can respond accordingly:

  • Complete our RAAC reporting form, or
  • Call us on 020 8555 1200 ext 89170 during office hours (Monday - Friday, 9am – 5pm)

Should you need further advice on RAAC then contact your local authority, or for fire safety concerns, contact us via our contact us form, or see our fire safety pages.

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