RAAC Remediation: CFRP Strengthening as an Alternative to Replacement
Reinforced Autoclaved Aerated Concrete (RAAC) in a roof or floor does not always mean full replacement. Where a structural assessment allows, Structured Carbon strengthens RAAC in place using carbon fibre reinforced polymer (CFRP), restoring capacity with far less cost, programme and disruption than stripping the structure out. Our engineering is led by John Staves, an award-winning structural engineer and one of the UK’s foremost RAAC specialists.
Schedule an InspectionA specialist partnership, and a UK first
Structured Carbon is the first company to commercially produce a bespoke, end-to-end CFRP solution designed specifically for RAAC. It is run as a specialist partnership: Neil Smuts (MCIOB, MInstNDT), President of the UK Concrete Scanning Standard (UKCSS) and a Fellow of the Register of Concrete Scanning Professionals, carries out the survey, scanning and monitoring, and John Staves (CEng FIStructE), one of the UK’s most highly regarded RAAC structural engineers, leads all of the calculations and design. John received the Innovation Award at the HSBC Commercial Banking and Federation of Small Businesses (FSB) Small Business Growth Awards for his work on RAAC repair. Together we take a scheme from first assessment through to installation and long-term monitoring.
What RAAC is, and why it needs attention
RAAC is a lightweight, aerated form of concrete used widely in roof panels, and far more rarely in floors, between the 1950s and mid-1990s. Unlike traditional reinforced concrete it has a cellular structure with limited reinforcement and lower durability, and after decades in service some panels can deteriorate, deflect or fail with little warning. That is why RAAC across schools, hospitals and public buildings has moved up the agenda, and why owners need a clear, proportionate plan rather than reaching straight for demolition.
The remediation options
Once a survey has identified RAAC and a structural engineer has assessed its condition, the realistic responses usually fall into a few categories:
- Monitoring and management where panels are assessed as low risk.
- Temporary propping to make an area safe while a permanent solution is designed.
- Strengthening to restore the capacity of the existing panels and extend their safe service life.
- Full replacement of the RAAC structure, the most costly and disruptive option.
CFRP strengthening sits in the third category, and in suitable cases it lets an owner avoid jumping straight to replacement.
CFRP strengthening for RAAC
CFRP strengthening bonds high-strength carbon fibre laminates or fabrics to the RAAC element to add tensile and shear capacity exactly where the assessment shows it is needed. The carbon fibre is light, thin and externally bonded, so it adds strength without adding significant load and without the demolition that replacement demands. Structured Carbon specialises in this approach for RAAC, with the engineering led by our partner John Staves so the strengthening is designed and verified by a recognised RAAC authority.
Engineered for your building, not off the shelf
Effective RAAC strengthening cannot be a one-size-fits-all product. RAAC is a low-strength, lightweight material, so the reinforcement has to be matched to it and to the specific loads of each structure. Our CFRP is designed and manufactured in the UK for each application, building and roof. Rather than a single fixed system, it is built from a range of elements that are tuned to deliver the exact strength the calculations require, no more and no less than the structure needs, each time and every time. We produce it in our own UK facility, including small bespoke batches of as little as ten or a hundred linear metres, and the system is in production now, so we can mobilise quickly.
The 5 Point RAACSafe™ Protocol
Every RAAC remediation we deliver follows our five-stage RAACSafe™ Protocol, an end-to-end process that takes a structure from first survey through to long-term monitoring.
- Assess. Neil Smuts surveys, scans and assesses the RAAC, identifying the panels, their condition and the loads they carry.
- Design. John Staves carries out the structural calculations and designs the bespoke CFRP strengthening scheme to suit the assessed condition.
- Manufacture. The CFRP solution is produced bespoke to that design, the step that makes our service genuinely end-to-end rather than off-the-shelf.
- Install. The CFRP system is applied in place to the engineered design, keeping disruption to a minimum and the building in use where possible.
- Monitor. Ongoing monitoring confirms the strengthened structure continues to perform as designed.
Where it is used
- Schools and education buildings
- Hospitals and healthcare estates
- Public sector and local authority buildings
- Commercial and industrial roofs and floors
Why CFRP instead of full replacement
- Less disruption – work is carried out in place, often keeping the building partly in use.
- Faster programme than stripping out and rebuilding the structure.
- Lower cost in suitable cases, with the existing structure retained.
- Lightweight reinforcement that adds capacity without significant added load.
Have RAAC in your building?
Tell us about the structure and any assessment already carried out, and we will advise whether CFRP strengthening is a viable remediation route.
Schedule an InspectionFrequently asked questions
- Can RAAC be strengthened instead of replaced?
- In many cases, yes. Where a structural assessment confirms it is suitable, CFRP strengthening can restore capacity to RAAC planks and keep a building in use, avoiding the cost and disruption of full replacement. The decision always rests with the responsible structural engineer.
- What is CFRP strengthening of RAAC?
- CFRP (carbon fibre reinforced polymer) strengthening bonds high-strength carbon fibre laminates or fabrics to the RAAC element to add tensile and shear capacity. It is a lightweight, externally bonded reinforcement applied after assessment and design.
- Is CFRP remediation faster than replacing RAAC?
- Typically. Externally bonded CFRP is applied in place without removing the roof or floor structure, so it is usually quicker and far less disruptive than stripping out and replacing RAAC planks, often allowing the building to remain partly in use.
- Which buildings have RAAC that may need remediation?
- RAAC is most commonly found in the roofs, and far more rarely the floors, of buildings constructed between the 1950s and mid-1990s, including schools, hospitals, and public and commercial buildings. A specialist survey identifies the planks and their condition.
- Does CFRP strengthening need engineer sign-off?
- Yes, and we provide it. Our structural engineering partner John Staves, an award-winning RAAC specialist, leads the assessment, design and verification of every scheme, so the engineering is handled by a recognised RAAC authority. We also work alongside your own engineer where you have one.