RAAC

What is Reinforced Autoclaved Aerated Concrete (RAAC)?

RAAC is a reinforced form of lightweight concrete used to form panels or planks. It has no aggregate unlike common concrete. These were mainly used in flat roofs but also in some floor and wall panel construction in the UK from the mid-1950s to the mid-1990s. There is evidence that it has been used in a limited number of buildings through the 1990’s and 2000’s. RAAC was used in a range of building types, both public and private sector, but is believed to be more common in schools, hospitals and public buildings. It has been discovered in courts, theatres, sports halls, public toilets, and a range of non-domestic buildings. It’s use in residential buildings is thought to be limited to roof top plant rooms, and some wall panels.

Why are there concerns about RAAC? 

RAAC has proven to be not as durable as other concrete building materials. It has a variable service life which is influenced by many factors and an arbitrary time, such as the widely reported ‘30 years’ life span, should not be the deciding factor when decision making as it can last longer if the building is well maintained and the original design factors haven’t changed, (such as calculated load weights). There is a risk it can fail, particularly if it has been damaged by water ingress from leaking roofs which causes corrosion of the reinforcement, excessive thermal degradation, or if it was not formed correctly when originally made.  Poor original installation, cutting the reinforcement bars on-site, can dramatically reduce the end bearing capacity of the planks. It can fail suddenly, hence the recent action by the UK Government. Later RAAC planks are known to use galvanised steel or stainless steel reinforcing bars, and are of less concern provided the roof is kept watertight.

Can I tell if my building has RAAC?  

Our advice to the public is not to attempt to identify whether there is RAAC in your buildings, or to assess the condition of known RAAC planks yourself. Due to the nature of the material, defects can be difficult to identify. If you are unsure whether your building includes RAAC, then you should use a suitably qualified professional, such as an RICS chartered building surveyor or chartered structural engineer. Regular Planned Preventative Maintenance (PPM) surveys should assist in identifying and managing potentially defective materials.

Does my building contain RAAC? 

The steps for an owner or building manager to take in identifying RAAC planks would include the following:

– Note that RAAC planks were used from the mid 1950s until the early 1990s, so buildings (or extensions) built before or after this period are unlikely to be affected.

– Ask the local authority whether any similar buildings to yours in the area are known to have RAAC roof or floor planks.

– Check any records about the construction to see if RAAC is mentioned. But be aware that RAAC may not be mentioned even when it was used. Note that certain product names such as Siporex, Durox, Celcon, Hebel and Ytong are indicators of RAAC.

– If you do not know the construction type of a roof but it could be RAAC planks, then the roof should be inspected by a suitably qualified and appropriately experienced professional, such as an RICS chartered building surveyor or chartered structural engineer, who is experienced with this type of construction.  Suitably qualified professionals are detailed on page 16 of the Department for Education guidance.

After inspection and identification, put in place measures to manage the risk e.g. temporary propping under the roof.  The remedial works advised will be risk-based for priority and what is most appropriate.  The use of the space beneath a roof will affect the risk assessment e.g. a classroom will be a higher risk than a storeroom or plant room.

There are reports of unqualified traders and scammers who are cold calling households offering RAAC surveys, according to Trading Standards. Always ensure that a qualified experienced competent professional who is a member of a regulated professional body such as the RICS and/or IStructE is employed for such work.

The designer’s duties (and general duties) will always apply, but where you are also likely to be the lead designer or a sole designer for building work (we do not include infrastructure works for this purpose, as the lead will likely be an engineer), you may have further duties as we explore below.

Where there is more than one contractor, or it is reasonably foreseeable that more than one contractor will be working on a project, the client must appoint in writing (a) a designer with control over the design work as the principal designer for the purposes of these regulations, and (b) a contractor with control over the building work as the principal contractor for the purposes of these regulations. These roles are also referred to as the principal dutyholders.

A principal designer must be appointed in writing before the construction phase begins, or before submitting an application for building control approval for a higher-risk building.

For domestic clients, the client duties will be carried out by the contractor (where there is only one contractor for the project), the principal contractor or principal designer (where the principal designer agrees to fulfil those duties with the client, agreed in writing).  If a domestic client fails to make the appointments the designer in control of the design phase of the project (most likely an architect) is the principal designer, as under CDM.

Organisations may also act as principal designer subject to necessary organisational capability, meaning possessing a robust management system and a team of staff members with relevant competence.

Where you are taking over from another principal designer, you will require due diligence to ensure duties to that point have been discharged in accordance with requirements, to satisfy yourself (or your organisation) that the building design and building works (as applies at appointment) are compliant.

Does RAAC pose a health risk? 

The concerns about RAAC are solely linked to its durability and structural performance. There is no evidence to suggest it poses any other health risk.

You may have heard some reports linking RAAC to asbestos. This is because some buildings built with RAAC were built at a time when asbestos was still legal to use, but there is no link between RAAC and asbestos.

Before any construction remediation of RAAC work takes place there are legal procedures to follow to manage any asbestos risk.  Remediation of RAAC will take into account asbestos identification on the specific site in the location of the work, and careful management if it is present.

With all that being said, it is also possible to have two appointments, where one person (or organisation) is unable to fulfil the competence requirements to perform the duties. Where a principal designer is no longer competent or their appointment ceases before the project is complete, the client must appoint a new principal designer or new principal contractor.

Do you need to vacate your building / area during a specialist survey? 

Where RAAC is known to be in place it is likely that a responsible body, for example the UK Government Department for Education, will have advised you to vacate the building if there are immediate risks for safety reasons.

If you are unsure if your building contains RAAC, follow the steps above and appoint a suitably experienced professional, such as an RICS chartered building surveyor or chartered structural engineer. We advise and encourage everyone to report any concerns about the buildings they are working in, to the responsible individuals.

How long does remediation take and how much does it cost?

Careful planning of any remediation works will vary from building to building, and it is not possible to provide definitive guidance on how long remediation might take. Removal of a RAAC flat roof for example may include the opportunity to redesign the roof involving planning and building regulations considerations.

Similarly, the cost of remediation will vary due to a large number of factors, including size of the building, location, temporary works such as a temporary roof etc.

Following the initial emergency remedial work or replacement of RAAC, RICS members can assist responsible bodies and owners with Planned Preventative Maintenance, which can help prolong the life of a building, identifying and addressing issues before they become critical safety concerns. This assists with both public budget planning and avoiding consequential effects on people, families and society.

List of schools affected by RAAC

The list of schools and colleges where the presence of RAAC was confirmed by 16 October has been published, here, on Gov.uk. 214 cases have now been confirmed.