Grenfell Tower tragedy, Aluminium Composite Material (ACM), Ministry of Housing, Communities and Local Government (MHCLG), Building Safety Programme, British Standards BS 476: Part 6 Fire Propagation, BS476: Part 7: 1997 Surface Spread of Flame test, BS 8414 Fire performance of external cladding systems, BR 135 Certificate, Building Defects Investigations.
Following the Grenfell Tower tragedy the Ministry of Housing, Communities and Local Government (MHCLG) has established the Building Safety Programme to assist landlords and building owners to identify buildings which are of concern through a detailed checking and testing process and to make sure that residents are safe, now, and in the future.
Non-Aluminium Composite Material (ACM) external wall insulation (EWI) systems with render finishes have proven to be robust and resilient in use in the United Kingdom exposure (sun, wind, rain, frost) conditions for over 40 years, and when installed in accordance with independent third-party certification requirements incorporating, where appropriate, fire barriers compliant with the design principles of BR 135 Fire performance of external thermal insulation for walls of multi-storey buildings, should prevent fire spread and remain securely attached to the external facade of buildings in real life fires.
Fig 1. BS 476 Pt 7 Small Scale Fire Test
Fig 2. BRE Multi-Storey Full-Scale Fire Test
However, a number of the external wall insulation (EWI) systems with render finishes already installed on existing homes incorporating combustible plastic insulation rely on BS 476 small-scale fire tests which cannot incorporate fire barriers and design principles within the test specimens to investigate the potential behaviour in fire of “as installed” external wall insulation cladding systems. The only way these can be incorporated to assess the effective fire performance is to test the complete system at large full-scale.
For details click on: Cladding Fire Risk Investigations
The Ministry of Housing, Communities and Local Government (MHCLG) has concluded that the current British Standard 8414 Fire performance of external cladding systems full-scale test is a robust test which provides the basis for a BR 135 classification and should be available from manufacturers and external wall insulation system designers.
Fig3. EWI Cladding Collapse – High-Rise
Fig4. EWI Cladding Collapse – Low-Rise
Building owners and managers of multi-occupied residential premises of any height should note the advice in The Ministry of Housing, Communities and Local Government (MHCLG), Advice for Building Owners of Multi-storey, Multi-occupied Residential Buildings, which requires building owners and managers to review the design of external wall insulation systems, and to inspect and assess the composition and installation of these systems to avoid fire risks “irrespective of the height of the building”. In particular, see section 8. External Wall Insulation (EWI) systems with a render or brick-slip finish, concerning “parts of the EWI system falling from buildings” and installation defects such as poor water-tightness.
For details of EWI systems falling from buildings, click on: External Wall Insulation (EWI): Advice for Building Owners
If not undertaken recently, building owners should consider an immediate review of the external wall insulation cladding on their buildings.
Building owners should take care in the selection of a competent person to carry out this assessment work as it is highly unlikely that a typical fire risk assessor or building surveyor will be appropriately qualified and have suitable long-term experience of external wall insulation systems’ various materials, components , design and installation requirements to conduct such a review and assessment and may be reluctant to undertake this work, and building owners may find they have to commission a suitably qualified expert to conduct a separate assessment. This is critical for ensuring that an appropriate level of safety is achieved and may require advice from a qualified engineer with relevant experience in fire safety, including the fire testing of these systems, such as a Chartered Engineer from the built environment profession registered with the UK Engineering Council with suitable experience in the fire safety of high-rise residential buildings where a system that should have a BR 135 Certificate does not have one.
The full guidance contained in the MHCLG Building Safety Programme should be helpful to all building owners and managers involved in conducting investigations of the fire risks associated with external wall insulation (EWI) systems with a render or brick-slip finish on their homes.