The testing was carried out on a non-load bearing steel frame, in accordance with BS-8414 part 2 – a testing standard which applies in UK building regulations.
It failed when measured against Australian standards due to a “significant pool fire” of molten melted insulation and flame spread above the top of the rig. Only the second of these would be relevant under the UK testing standard.
However the large pool of burning plastic suggests a risk that a fire in an EPS-clad block could spread down a building as well as upwards.
The fire spread to the top of the system within eight minutes and the one-hour test had to be extinguished after just 12 minutes.
“If the system had been installed to a taller wall with more levels, the fire would have continued to spread to all levels above,” the report said.
“The system resulted in flaming molten EPS forming a large pool fire at ground level. This indicated that the system would be prone to downward fire spread to the base of the wall, balconies or other horizontal projections located below the level of fire origin.”
The report ran a direct comparison with the post-Grenfell fire tests carried out by the Building Research Establishment in the UK and concluded the two systems had similar times to temperature monitors exceeding the 600 degree celsius threshold and flaming at the top of the rig.
“Based on the above, it can be concluded that, although the rendered EPS and [ACM] wall systems are constructed of significantly different products/materials the propensity for rapid fire spread when exposed to a large fire source is similar,” the report said.
The government refused to test EPS systems in September 2019 when asked by London boroughs because “we know they are flammable”, minutes obtained by Inside Housing show.
However, government ministers have repeatedly said ACM systems are more dangerous.
As a result, while there is direct government funding for all ACM cladding removal, EPS systems are required to compete with other non-ACM products for extremely limited additional removal funding.
Dr Jonathan Evans, chief executive of building envelope firm Ash & Lacy, told Inside Housing: “This calls into question the guidance that’s been given and clearly shows these materials have the capacity to spread fire. These systems are extremely common, the vast majority of rendered systems are EPS backed.”
Update at 6.05pm on 11.12.2020: an previous version of this article referred to extruded rather than expanded polystyrene. This was corrected.