CLADDING & SHEETING
A clearer path for the
future of ACM cladding
After a year in limbo, there is now increasing clarity in the construction industry about the fire performance
of rainscreen cladding systems on buildings over 18 metres. Nick Jenkins, executive director at architectural
cladding specialist Booth Muirie, which is part of the Euroclad group of companies, discusses
I’ve been involved in an
unprecedented number of fire tests in
the sector, gaining an insight into the
way aluminium and ACM rainscreen
cladding systems behave during a fire.
The extensive testing of complete
systems is now providing professionals
with the clarity and reassurance they
need, and I urge the architectural and
construction communities to take a
closer look at the detailed performance
of rainscreen cladding systems to ensure
safer specification.
Following the Grenfell Tower tragedy,
the government established a Building
Safety Programme with the aim
of ensuring high-rise residential
buildings are safe and that
residents feel safe in them.
Rainscreens were thrown
into the spotlight as part of the
investigation and, a year on
from the tragic events in North
Kensington, many people in the
construction industry are still unsure
about, or lack confidence in the systems.
Performing within the limits
The British Standard large-scale test (BS
8414) sets out a standard methodology for
assessing the resistance to spread of fire
performance of multi-layered wall systems.
If the system performs within the limits
set out in BR 135 when tested, it is a way of
demonstrating that the precise assembly
constructed for the test meets with Building
Regulations for buildings with storey
heights above 18 metres.
To date, a number of different
multi-layered wall assemblies featuring
rainscreen cladding systems which can be
supplied by Booth Muirie have been tested
according to the BS8414 fire test standard.
So far 17 assemblies featuring Booth
Muirie’s panel systems have satisfied the
requirements of BR 135.
The testing, which is ongoing, has been
carried out in conjunction with multiple
industry partners and represents the most
comprehensive and wide-ranging testing
programme of solid aluminium and ACM
cladding systems ever undertaken.
The work provides unequivocal
information on these systems, giving us
confidence in what to advise the industry
and to support the provision of safer
specifications for the future.
“As an industry, it is our
responsibility to ensure the
safety of the modern built
environment. Professionals
need to take all of the
findings available to them
and use them to make
better informed and safer
specifications to restore
confidence in the cladding
industry”
Clarity for the future
We chose to share all of our findings on our
website to give the construction industry
some much needed clarity going forward,
helping them to make informed choices
and improving safety in buildings over 18
metres. We believe these findings will help
make positive changes across the industry.
We have gained an excellent
understanding of the effects that changes
in design can have on a wall assembly’s
resistance to spread of fire performance
through this comprehensive testing.
We found that there are many different
factors that can dramatically affect how
a system featuring aluminium or ACM
rainscreen panels will perform in the event
of a fire. Even the subtlest of changes can
have a big impact on its behaviour.
The evidence that we have gathered
to date suggests that the primary
determinants of a system’s performance in
respect to its resistance to spread of fire are
the type of external cladding material used
and the cavity barrier detailing.
If the external cladding material is an
ACM, then the system’s performance cannot
just be delineated by the calorific value of
the core. The way this core is bonded to the
aluminium surface layers of the composite
also has a huge bearing on performance.
Insulation type, thickness and cavity size
also influence performance, but to a much
lesser extent.
Evidence-based understanding
Given that there are so many different
factors affecting behaviour in fire, the
truest indication of real-life performance
is always going to be an evidence-based
understanding – that is an assembly of
specific components that has been fitted in a
detailed manner, tested to the BS8414 test(s)
and proven compliant with BR135.
It is, however, an expensive route.
Multiple assemblies may have to be tested
for any one project (and re-tested for
any change in specification at any point)
and, with only limited testing facilities
available globally, there is currently a
testing capacity issue in the industry.
Desktop studies can be a more viable
option when based on tested products
and systems, helping to demonstrate
compliance when the demand for testing
exceeds the capacity.
The studies can be improved by
combining them with intermediate scale
testing of variants or by applying an
extended field of application (EXAP),
where a group of products with similar
attributes can be classified in relation to
the reaction to fire, without testing every
product individually.
As an industry, it is our responsibility
to ensure the safety of the modern built
environment.
Professionals need to take all of the
findings available to them and use
them to make better informed and safer
specifications to restore confidence in the
cladding industry.
w www.boothmuirie.co.uk
Above:
Nick Jenkins,
executive
director
business
development
at Booth Muirie
32 www.rcimag.co.uk July 2018
/www.boothmuirie.co.uk
/www.rcimag.co.uk
/www.boothmuirie.co.uk
/www.rcimag.co.uk
