Although plans are afoot to remove or strengthen RAAC where necessary in public buildings, that does not completely remove the risk, as it was also installed in the private sector, according to the Institution of Structural Engineers. It says: “As such, it is advised that any private asset owner, with properties constructed between the mid-1950’s and mid-1990’s, conduct a survey of the building to identify or eliminate the possibility of RAAC within the fabric where necessary.”
It adds: “If properly designed, manufactured, in good condition and with good bearing, RAAC installations are considered safe. However, the panels can creep and deflect over time, and this can be exacerbated by water penetration. A more recent incident indicated that if they have insufficient bearing and their structural integrity is compromised, they can fracture and collapse with little or no warning.”
The organisation continues: “Our advice, alongside that of Collaborative Reporting for Safer Structures UK (CROSS-UK), is that if a building owner or manager has a building from this period and is unsure of the form of construction, they should carry out an inspection and a risk assessment. If RAAC planks are present, their structural condition will need to be determined,” by a qualified engineer.
On the exact qualifications required, the body’s recommendations differ from that of government. It recommends using a chartered or incorporated structural engineer (and provides a list via www.is.gd/opusor).
The Department for Education’s stipulations were stricter in its August 2023 document, ‘Reinforced autoclaved aerated concrete: identification guidance’. It says: “Having identified that a premises may contain RAAC or if you are unsure, assistance should now be sought from an appropriately qualified building surveyor or structural engineer with experience of RAAC.” It adds that the latter should be chartered members of either the Institution of Structural Engineers or the Institution of Civil Engineers, with evidence of relevant experience. “Evidence of RAAC experience is essential,” it says. Although building surveyors, needn’t be chartered, they should have, in addition to a relevant degree, three years’ experience assessing building condition, and at least a year’s experience of RAAC project work.
That document points out that telltales of RAAC are the width of the panels – 600mm wide, or about two feet – and distinctive V-shaped grooves which mark a chamfer along the edge.
The Institution of Structural Engineers points out that, depending on the results of the survey, “a process of ongoing monitoring and/or remedial propping or strengthening works may be needed. In some instances, it may be necessary to remove or replace RAAC planks.”
BOX: SOURCES OF INFORMATION
The Department for Education proposes that useful and relevant information about the use of RAAC (suppliers of which include Siporex, Durox, Celcon, Hebel and Ytong) might be found in historical building records, and provides examples below.
1. Construction dates for different blocks/parts of school, alterations, extensions or interventions: that is, where RAAC panels may have been used, or an adaptation to RAAC panels within existing buildings
2. Drawn information, including historic building plans, sections and elevations together with any detailed construction drawings, re-roofing works, confirmation of any works that may have been undertaken and the reasons why, for example ponding or leaking
3. Photographs during construction, rebuilding works, alterations, repairs
4. Building specifications, condition, or investigation reports
5. Building services systems and revisions that may have altered loading, required fixings into roof or floor systems, or altered internal environments within a space. For example, solar PV panels added to roof; conversion of upper floor to library/science lab; new kitchen
6. Asbestos register.