Statutory Inspections · Mandatory · Pre-Construction

RAAC Inspection and Assessment Record

An inspection and structural assessment record for Reinforced Autoclaved Aerated Concrete (RAAC) in pre-1980 buildings. RAAC has exceeded its 30-year design life and can collapse without warning. Covers desk study, visual inspection, intrusive investigation, structural engineer assessment (moisture, carbonation, reinforcement corrosion, load capacity), risk rating, and construction works restrictions. Workers must never walk on RAAC roof planks without assessment.

Last reviewed: 2 April 2026 — This guide reflects UK law as of this date. MHSWR 1999 / HSWA 1974 / HSE RAAC Guidance 2023 remains current with no amendments enacted as of 2 April 2026. Next scheduled review: 2 April 2027.

Template reference	T19 RAAC Inspection & Assessment Record
Primary legislation	Management of Health and Safety at Work Regulations 1999 (MHSWR) / Health and Safety at Work etc. Act 1974 (HSWA)
Key guidance	HSE RAAC Guidance 2023 / Institution of Structural Engineers RAAC Guidance
Buildings at risk	Pre-1980 buildings with flat or low-pitch roofs — particularly schools, hospitals, and public buildings
Design life	RAAC was designed for a 30-year lifespan — all RAAC installations have now exceeded this
Collapse risk	RAAC can collapse without warning — progressive deterioration is not always visible externally

1. What It Covers

Reinforced Autoclaved Aerated Concrete (RAAC) is a lightweight form of precast concrete that was widely used in the UK from the mid-1950s to the mid-1980s, primarily for roof decks in flat-roofed buildings. RAAC planks were used extensively in schools, hospitals, colleges, government buildings, and some commercial and industrial premises. The material was designed with a lifespan of approximately 30 years — meaning that all RAAC installations have now significantly exceeded their intended design life.

RAAC is structurally different from conventional reinforced concrete. It is aerated (cellular), making it much lighter but also weaker and more porous. Over time, RAAC deteriorates through carbonation, moisture ingress, and corrosion of the internal reinforcement. The critical danger is that RAAC can fail suddenly and without warning — a roof plank that appears sound from below can collapse under its own weight, under imposed loads (such as roofing materials, plant, or a person walking on it), or as a result of water damage that has weakened the internal structure.

The HSE RAAC Guidance published in 2023 and the Institution of Structural Engineers guidance set out the process for identifying, assessing, and managing RAAC in existing buildings. For any construction project involving a pre-1980 building with a flat or low-pitch roof, the RAAC Inspection and Assessment Record documents the investigation, structural assessment, risk rating, and recommendations that must inform the construction phase plan and pre-construction information.

Workers must NEVER walk on or load RAAC roof planks without structural assessment

Fatalities have occurred from RAAC roof collapses. RAAC planks can appear sound from below while being severely deteriorated internally. No person should walk on, stand on, or place any load on RAAC roof planks until a structural engineer has carried out a full assessment and confirmed that the planks can safely support the intended loads. If there is any doubt about whether a roof contains RAAC, it must be treated as RAAC until proven otherwise, and access must be prohibited until assessment is complete.

2. Key Content

The following table sets out the information that must be recorded in the RAAC Inspection and Assessment Record.

Element	Detail
Building reference	Building name, address, and unique reference. Year of construction (or estimated decade if exact date unknown). Building type and current use. Original construction drawings and specifications if available.
INITIAL RAAC INVESTIGATION — Desk study	Review of original construction drawings, specifications, and structural calculations to identify whether RAAC was specified. Review of previous survey reports, maintenance records, and any known water ingress history. Contact with the original design team or building owner for construction records.
INITIAL RAAC INVESTIGATION — Visual inspection	External inspection of the roof for signs of RAAC: flat or low-pitch profile, precast plank construction, visible plank joints. Internal inspection from below for characteristic RAAC appearance: textured/porous surface, plank widths typically 300–600mm, visible joints between planks. Note any signs of deterioration: cracking, spalling, staining, deflection, or damp patches.
INITIAL RAAC INVESTIGATION — Intrusive investigation	Where the desk study and visual inspection suggest RAAC may be present but cannot be confirmed, intrusive investigation is required. Core samples taken from representative planks and tested to confirm material composition. Carbonation depth testing. Assessment of reinforcement condition (corrosion, section loss). This must be carried out by a suitably qualified structural engineer.
STRUCTURAL ASSESSMENT — Structural engineer	Name, qualifications (CEng, MIStructE or equivalent), and organisation of the structural engineer carrying out the RAAC assessment. The assessment must be carried out by a chartered structural engineer with experience of RAAC.
STRUCTURAL ASSESSMENT — Assessment date	Date the structural assessment was carried out. Assessment validity period (typically 12 months for critical condition RAAC, up to 3 years for RAAC in good condition, subject to the engineer's recommendation).
STRUCTURAL ASSESSMENT — RAAC condition	Condition assessment of each RAAC element inspected: good (no visible deterioration, adequate cover to reinforcement, no moisture ingress), fair (minor cracking or carbonation, adequate structural capacity), poor (significant deterioration, moisture ingress, reinforcement corrosion, reduced structural capacity), or critical (immediate risk of failure, load-bearing capacity compromised).
STRUCTURAL ASSESSMENT — Load capacity assessment	Assessed load-bearing capacity of the RAAC planks compared to the imposed loads (dead load, live load, wind load, maintenance loads). Confirmation of whether the planks can safely support their current loading, any proposed additional loads from construction works, and the weight of a person for maintenance or construction access.
STRUCTURAL ASSESSMENT — RISK RATING	Overall risk rating assigned by the structural engineer: low (RAAC in good condition, adequate capacity, no immediate action required), medium (some deterioration, monitoring required, restrictions on loading), high (significant deterioration, immediate restrictions on access and loading, remedial works required), or critical (immediate risk of collapse, area must be evacuated and propped or removed).
STRUCTURAL ASSESSMENT — RECOMMENDATIONS	Specific recommendations from the structural engineer: monitoring regime, access restrictions, load restrictions, propping requirements, remedial works, replacement programme, or immediate evacuation. Recommendations must be incorporated into the construction phase plan and pre-construction information.
For construction works	Where construction works are planned in or on a building containing RAAC: confirmation that the RAAC assessment has been provided to the principal designer and principal contractor as part of the pre-construction information. Method statement for working in proximity to RAAC. Exclusion zones below RAAC planks (where required). Propping arrangements. Monitoring during construction.
Re-assessment date	Date by which the RAAC must be re-assessed. Set by the structural engineer based on the condition and risk rating. Critical or high-risk RAAC may require re-assessment within 6–12 months. Lower-risk RAAC may be re-assessed at 2–3 year intervals.

3. Common Mistakes

Not including RAAC investigation in pre-construction information

CDM 2015 requires the client and principal designer to provide pre-construction information that includes information about significant hazards. For any project involving a pre-1980 building with a flat or low-pitch roof, the possibility of RAAC is a foreseeable hazard that must be investigated and documented. Failing to include RAAC investigation in the pre-construction information means the principal contractor cannot plan safe working methods, and workers may unknowingly access or load RAAC elements without assessment.

Relying on visual inspection alone without intrusive investigation

RAAC can be concealed behind suspended ceilings, plasterboard linings, or paint finishes. A visual inspection from below may not identify RAAC, and even where RAAC is visible, the surface appearance does not reliably indicate the internal condition. Carbonation, moisture ingress, and reinforcement corrosion can be extensive without visible external signs. Where RAAC is suspected, intrusive investigation (core samples, carbonation testing, reinforcement assessment) is essential to determine the actual condition.

Allowing workers to access the roof without structural assessment

No person should walk on, stand on, or place any equipment on a roof that contains or may contain RAAC until a structural engineer has confirmed that the planks can safely support the intended loads. RAAC planks have collapsed under the weight of a single person. The default position must be that roof access is prohibited until the structural assessment confirms it is safe, and even then, access should be via crawl boards or other load-spreading measures as recommended by the engineer.

Not monitoring RAAC during construction works

Construction works can generate vibration, impose additional loads (from scaffolding, plant, or stored materials), and disturb the building fabric in ways that affect RAAC stability. Where RAAC is present in a building undergoing construction works, the structural engineer's monitoring recommendations must be followed throughout the construction phase. This may include regular visual inspections, deflection monitoring, and load restrictions. Changes in condition must be reported to the structural engineer immediately.

4. Frequently Asked Questions

What does RAAC look like?▾

RAAC has a distinctly different appearance from conventional concrete. It is cellular and porous — when you look at a broken or cut surface, you can see the air bubbles (cells) that give it its lightweight properties. The surface is typically rough and textured, lighter in colour than dense concrete, and dull grey. When tapped, RAAC produces a hollow, dull sound rather than the sharp ring of dense concrete. RAAC planks are typically 300–600mm wide and span between structural beams or walls. If you are unsure whether a material is RAAC, treat it as RAAC until a structural engineer confirms otherwise.

Which buildings are most likely to contain RAAC?▾

RAAC was used primarily in flat-roofed buildings constructed between the mid-1950s and the mid-1980s. The building types most commonly affected are schools (particularly system-built schools from the 1960s and 1970s), hospitals, colleges, government offices, courts, police stations, and some commercial and industrial buildings. RAAC was rarely used in domestic construction. The highest concentration of RAAC is in the public estate — the Department for Education identified RAAC in over 200 school buildings during its 2023 survey programme.

Can RAAC be repaired or does it need to be replaced?▾

It depends on the condition. RAAC in good condition with minimal carbonation and no reinforcement corrosion can be managed through monitoring, waterproofing the roof membrane (to prevent moisture ingress), and restricting loads. RAAC in poor or critical condition typically requires replacement rather than repair. Repair options (such as additional waterproofing or localised patching) do not address the fundamental issue of reinforcement corrosion and carbonation, which are progressive and irreversible. The structural engineer's assessment will determine whether monitoring, repair, or replacement is appropriate.

Is a RAAC assessment legally required before construction works?▾

There is no single regulation titled ‘RAAC Assessment Regulations.’ However, the legal duty arises from the general obligations under HSWA 1974 (duty to ensure the safety of persons at work and others affected by the works), MHSWR 1999 (duty to carry out a suitable and sufficient risk assessment), and CDM 2015 (duty to provide pre-construction information about known or foreseeable hazards). If a construction project involves a pre-1980 flat-roofed building and the possibility of RAAC has not been investigated, the client, principal designer, and principal contractor are all potentially in breach of their statutory duties.

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