What Are the Fire Safety Requirements for External Cladding Systems?

Summary

The Grenfell Tower fire in June 2017, which killed 72 people, exposed catastrophic failures in the regulation, specification, testing, and installation of external cladding systems. The subsequent Hackitt Review and years of legislative and regulatory change have fundamentally restructured how external wall fire safety is regulated in the UK — particularly for higher-rise residential buildings.

Before Grenfell, Approved Document B permitted cladding systems on tall buildings to be assessed using large-scale fire tests, and interpretation of "limited combustibility" requirements was inconsistently applied. The 2018 amendment to ADB removed the large-scale test route for residential buildings over 18 metres and required cladding materials to achieve limited combustibility in their own right. This change has required significant remediation work across thousands of buildings.

The Building Safety Act 2022 went further, creating the Building Safety Regulator, introducing the higher-risk building (HRB) regime, and placing new obligations on dutyholders for design, construction, and occupation. EWS1 (External Wall System) forms, originally a RICS initiative for mortgage purposes, became a major mechanism for demonstrating that existing cladding had been assessed, though PAS 9980:2022 has since provided a more structured framework for that assessment.

Key Facts

• Legal basis — Building Regulations 2010; Approved Document B (amended 2018 and 2019); Building Safety Act 2022; Fire Safety Act 2021
• 18m threshold — The critical height above which the most stringent cladding requirements apply in England
• 11m threshold — Some requirements (e.g., EWS1 and certain remediation obligations) apply from 11m under leaseholder protections in the BSA 2022
• A1 classification — Non-combustible (e.g., brick, stone, concrete, glass, most metals) — no contribution to fire
• A2-s1,d0 — Limited combustibility; very limited fire growth contribution; smoke and droplet limitations — the minimum for cladding materials on buildings over 18m
• Class B and below — Not acceptable as the primary cladding material on higher-risk residential buildings
• ACM (Aluminium Composite Material) — Polyethylene-core ACM (type 4) was used at Grenfell; identified as most dangerous; has been removed from most high-rise buildings
• HPL (High Pressure Laminate) — Another combustible cladding type; identified in subsequent surveys as a risk on many buildings
• EWS1 form — Assessment document confirming external wall fire safety; required by many lenders for mortgage purposes
• PAS 9980:2022 — Code of practice for fire risk appraisals of external wall construction and cladding
• FRAEW (Fire Risk Appraisal of External Wall) — The assessment process under PAS 9980:2022; must be carried out by a suitably qualified professional
• Building Safety Act 2022 — Established the Building Safety Regulator; created the higher-risk building regime; introduced leaseholder protections
• Responsible persons (BSA 2022) — Accountable person, principal accountable person (for HRBs over 18m/7 storeys); stringent new duties
• Remediation funding — Government-funded schemes and developer pledges apply to certain buildings; legal framework for cost recovery from developers/landlords

Quick Reference Table

Note: Scotland, Wales, and Northern Ireland have separate regulatory frameworks; thresholds and requirements differ.

Detailed Guidance

Post-Grenfell Regulatory Timeline

June 2017 — Grenfell Tower fire. 72 lives lost. ACM cladding with polyethylene core identified as primary fire spread mechanism alongside defective compartmentation.

2018 — ADB amendment (England). Approved Document B amended to prohibit combustible cladding on the external walls of buildings over 18m that contain flats. The large-scale test route (BS 8414) removed for these buildings. Materials must achieve A2-s1,d0 or better in their own right.

2019 — ADB further amendment. Extended the requirement to hospitals, care homes, and student accommodation over 18m. Also introduced a requirement that any cladding system (not just the primary cladding panel) must not include combustible materials in the thermal insulation, fire barriers, or adhesives on these buildings, unless a detailed assessment demonstrates acceptability.

2021 — Fire Safety Act. Clarified that the RRO applies to external walls, structure, and flat entrance doors of multi-occupied residential buildings. Triggered EWS1 process being a fire safety requirement, not just a mortgage question.

2022 — Building Safety Act. Created the Building Safety Regulator. Established the Higher Risk Building regime. Buildings over 18m (or 7 storeys) with 2+ dwellings must register, appoint an Accountable Person, and comply with the Gateway process for any new design and construction work.

2022 — PAS 9980. Published as the code of practice for Fire Risk Appraisals of External Walls. Replaced ad hoc approaches to EWS1 form completion. FRAEW assessments under PAS 9980 provide a structured, risk-based methodology.

Material Classifications

BS EN 13501-1 classifies reaction to fire performance:

The suffix s1 means very limited smoke production; d0 means no flaming droplets or particles. Both are required for A2 materials used on higher-risk buildings.

ACM and Other Identified Risk Cladding Types

ACM (Aluminium Composite Material) — Type 4 (polyethylene core): Used at Grenfell. Burns intensely. Government has funded removal from social housing blocks. Most private sector ACM cladding has been remediated. Some Type 1 (fire-resistant core) ACM may be acceptable subject to assessment.

HPL (High Pressure Laminate): Used on many buildings as an alternative to ACM. Combustible. Many buildings with HPL cladding have been identified as requiring remediation. Performance depends on specific product, thickness, substrate, and cavity design.

EPS (Expanded Polystyrene) insulation: Combustible. Common in External Wall Insulation (EWI) systems. Can support fire spread in wall cavities if not properly protected. Risk depends on fire barriers and overall system design.

PIR/PUR (Polyisocyanurate/Polyurethane) insulation: Combustible. Widely used behind various cladding types. Risk assessed on system basis.

Mineral wool (stone wool/glass wool): Class A1 or A2. The preferred insulation type for high-rise cladding systems. Used in remediation to replace combustible insulation.

EWS1 Process and PAS 9980:2022

The EWS1 (External Wall System 1) form was developed by RICS, UK Finance, and the Building Societies Association in 2019 to provide a consistent way for lenders to assess whether external wall fire safety had been properly evaluated on a building. The form has two key sections:

EWS1 Category A: Cladding is unlikely to be combustible — assessed by a suitably qualified professional. Often allows mortgage to proceed.

EWS1 Category B: Cladding is likely to be combustible or contains combustible elements — requires full fire risk appraisal by a qualified fire engineer and specific remediation or risk management measures.

PAS 9980:2022 provides the methodology for carrying out the fire risk appraisal (FRAEW) that underpins an EWS1 form. Key aspects:

• Assessment must be carried out by a suitably qualified professional (typically a chartered fire engineer)
• The assessment is risk-based, not prescriptive — a building with non-compliant materials may still be assessed as acceptable risk if other mitigating factors exist (sprinklers, fire detection, compartmentation)
• The output is a professional judgement, not a binary pass/fail
• PAS 9980 does not apply to buildings under 11m

The FRAEW assesses:

1. Ignitability of external wall construction
2. Fire spread potential within the wall system
3. Fire spread to and from the building
4. The potential for fire spread to affect means of escape

Leaseholder Protections under the Building Safety Act 2022

The BSA 2022 introduced significant protections for leaseholders in buildings with historic cladding defects:

• Qualifying leaseholders (those who owned the flat when the Act came into force and it was their principal home, or those who own no more than 3 dwellings in the UK) cannot be charged for remediation of relevant defects in buildings over 11m
• Developers who built the building are primarily liable for remediation
• Freeholders who are not associated with the developer may have capped liability
• Government-funded remediation schemes and developer pledge programmes apply to specific cohorts of buildings

Leaseholders should not simply pay cladding remediation service charges without understanding their legal protections. Building owners and managing agents must follow the BSA 2022 framework before passing costs to leaseholders.

Frequently Asked Questions

My building is under 18m — do the cladding rules not apply?

Some requirements still apply below 18m. ADB requires that external walls do not unduly promote fire spread, which is interpreted to require reasonable combustibility limits even on lower buildings. For buildings between 11m and 18m, EWS1 forms may be required by mortgage lenders, and the leaseholder protections under the BSA 2022 apply. For buildings under 11m, generally standard Building Regulations apply without the enhanced cladding restrictions, and EWS1 is not required.

What is the difference between ADB compliance and PAS 9980 assessment?

ADB compliance is a Building Regulations matter — it determines whether the building was built to the required standard at the time of construction. PAS 9980 assessment is a retrospective risk appraisal of the existing external wall construction, considering the actual conditions as they are now. A building may not fully meet current ADB requirements yet still be found to present acceptable risk under PAS 9980 if other factors mitigate the risk. The two frameworks serve different purposes and produce different outputs.

Who can sign off an EWS1 form?

The EWS1 form must be completed by a suitably qualified professional — the RICS guidance requires this to be a member of a relevant professional body with competence in external wall fire safety. For Category B buildings (combustible elements present), the assessment underpinning the form must be carried out by a qualified fire engineer. The number of qualified professionals able to carry out FRAEW assessments has been a significant bottleneck in the remediation process.

What about buildings in Scotland and Wales?

Scotland and Wales have their own Building Regulations and fire safety legislation. Scotland's height threshold for the most stringent requirements differs from England. Wales introduced a requirement for sprinklers in all new residential buildings regardless of height. Always check the relevant devolved regulations for buildings outside England.

Regulations & Standards

• Building Regulations 2010 (SI 2010/2214) and Approved Document B (2018 and 2019 amendments) — Combustibility requirements for external walls

• Building Safety Act 2022 — Higher-risk building regime, Building Safety Regulator, leaseholder protections

• Fire Safety Act 2021 — Extended RRO scope to external walls and structure

• PAS 9980:2022 — Code of practice for fire risk appraisals of external wall construction

• BS EN 13501-1 — Fire classification of construction products; reaction to fire

• BS 8414-1 and BS 8414-2 — Fire performance of external cladding systems (large-scale tests; no longer the primary route for 18m+ residential)

• BR 135 — Fire performance of external thermal insulation for walls of multi-storey buildings (assessment framework for BS 8414 tests)

• Regulatory Reform (Fire Safety) Order 2005 — Ongoing fire safety management

• Approved Document B (Fire Safety) — DLUHC official guidance

• Building Safety Act 2022 guidance — GOV.UK overview

• PAS 9980:2022 — BSI published standard for FRAEW assessments

• EWS1 process — RICS guidance — RICS guidance on external wall assessments

• Grenfell Tower Inquiry — Phase 2 Report — Findings and recommendations

• compartmentation — Fire compartmentation principles and maintenance

• fire risk assessment — Conducting and maintaining fire risk assessments

• passive fire protection — Passive fire protection systems for buildings

• waking watch requirements — When waking watch is required and how to transition away from it