Study finds external wall insulation EWI systems with render and brick slip finishes may pose fire risk to occupants of multi-storey tower block buildings.
Following a number of limited site investigations in early 1990s into fires involving external wall insulation (EWI) systems with render finishes on multi-storey dwellings, I-CAN staff approached the then Department of Trade & Industry (Dti) to share our findings and expressed our concerns that the current small-scale fire tests to BS 476: Part 6 Fire Propagation and BS476: Part 7: 1997 Surface Spread of Flame test conducted on small-scale samples only, not exceeding 50mm in thickness, in the following sizes:
Part 6 Sample size – 225mm x 225mm
Part 7 Sample size – 885mm x 265mm
and requirements for Class O, as defined in Approved Document B, Fire Safety (1992) of the Building Regulations 1991 were, in our opinion, inadequate to investigate the behaviour in fire of “as installed” external wall insulation cladding systems on multi-storey tower block buildings.
Fig 1. BS 476 Pt 7 Small Scale Fire Test
Fig 2. BRE Multi-Storey Fire Test
Fire is a particular known hazard in high-rise buildings and therefore design features are required to be incorporated to reduce or minimise the danger to occupants and property by detecting, extinguishing or containing any fire which may occur.
External wall insulation systems (EWI) with render finishes incorporating combustible plastic insulation must include horizontal fire barriers together with stainless steel mechanical fixings to prevent detachment of masonry finishes and be installed strictly in accordance with the requirements contained in the Building Regulations and relevant EWI system independent third-party Certification. These design features cannot be incorporated into the small-scale samples required for BS 476 Part 6 and Part 7 tests.
Consequently, we submitted an application to the Department of Trade & Industry (Dti) Partners In Technology Project (PiT), and were successful in obtaining joint PiT and industry funding to enable full scale BRE Multi-Storey Fire Tests to be conducted on an External Wall Insulation (EWI) Cladding System incorporating common alternative insulation materials in use in 1997.
Fig 3. External Wall Insulation (EWI) Cladding Fire
Fig 4. Cladding Fire – Bulging of EWI Render Finish
The installed external wall insulation system and alternative insulation materials incorporated where appropriate relevant design features to minimise danger to occupants from fire achieved satisfactory performance in each of the full-scale BRE multi-storey fire tests.
The outcome of these tests was shared with the Dti and leading manufacturers of Insulation materials.
Furthermore, I-CAN staff disseminated the outcome of the findings of these tests throughout industry via circulation in leading industry publications and through a series of presentations at major industry conferences throughout the UK. In particular, we emphasised that the test results were specific to the system as installed and tested, and that further BRE multi-storey fire tests would be required to be conducted to establish identical performance for other manufacturer’s installation specifications, alternative fire barrier details, insulation materials, polymer cement adhesives, renders and masonry paint finishes.
Following a fatal fire on the 11th June 1999 Involving plastic cladding to a 14-storey high-rise residential tower block at Garnock Court, Irvine, Ayrshire, we submitted the outcome of our PiT and industry funded fire risk investigations conducted in 1997 to the House of Commons parliamentary committee set up to review the, Potential Risk Of Fire Spread In Buildings Via External Cladding Systems.
The committee concluded:
“19. …., we do not believe that it should take a serious fire in which many people are killed before all reasonable steps are taken towards minimising the risks. The evidence we have received strongly suggests that the small-scale tests which are currently used to determine the fire safety of external cladding systems are not fully effective in evaluating their performance in a ‘live’ fire situation. As a more appropriate test for external cladding systems now exists, we see no reason why it should not be used.
- We believe that all external cladding systems should be required either to be entirely non-combustible, or to be proven through full-scale testing not to pose an unacceptable level of risk in terms of fire spread.”
The design of all fire-breaks in existing installed external wall insulation systems with render finishes is critical and checks should be conducted by building owners to ensure the installation is strictly in accordance with appropriate independent third party UKAS accredited certification requirements, Building Regulations (fire safety, and materials and workmanship) and any other regulations that relate to the installation of the measure.
I-CAN staff has been involved in assisting Local Authorities and Registered Social Landlords in carrying out inspections of fire damage and defects investigations to existing external wall insulation systems on multi-storey buildings and advising on the required remedial works.
If you require assistance in carrying out inspections of existing external wall insulation systems with render or brick slip masonry finishes on multi-storey buildings please click here to contact us.