Diales Compendium Issue 3 - Flipbook - Page 23
ISSUE 3
COMPENDIUM
“...simply following the guidance does not
guarantee that your building work will comply
with the legal requirements of the Building
Regulations.”
So, whilst the requirement at section 12.7 of ADB that: “In a
building with a storey 18m or more above ground level any
insulation product … used in the external wall construction
should be of limited combustibility …”, is unequivocal, the
arguments around cladding specifications are more nuanced,
however. Since the Grenfell fire, much of the ensuing debate
has understandably centred around Aluminium Composite
Material (‘ACM’) cladding systems.
In hindsight, it is tragically apparent that non-fire rated ACM
cladding panels did not meet the requirements of section
B4.(1) of the Building Regulations. Despite the product’s
evident failure to meet this statutory minimum, Paul Hyett,
an architect, and former president of the Royal Institute
of British Architects (‘RIBA’), does not believe that the
designer’s specification of the ACM cladding, of itself, was
unreasonable. In expert evidence to the Grenfell Inquiry, Mr
Hyett argued that the cladding system that was installed was
subject to a test certificate from the renowned British Board
of Agrément (‘BBA’) affirming that: “… the [ACM] panels
maybe regarded as having a Class 0 surface ...”.
Independently verified certificates published by the BBA are
intended to give specifiers peace of mind that products are
fit-for-purpose, safe, and comply with regulations and best
practice guidelines. ‘Class 0’ is the external wall surface
classification for the spread of flame, which is a prerequisite
for materials used on residential buildings 18m or higher, (or
closer than 1m from the boundary) under section 12.6 and
Diagram 40 (see Figure 1) of ADB.
Mr Hyett’s argument rests on the basis that the architectural
profession should be able to rely on manufacturers’ published
data and, particularly, BBA Certificates. Without confidence
in such technical information, the profession would be
‘fumbling in the dark’ and, if the elements of each and every
project had to be independently tested and certified, the
construction industry would effectively grind to a halt.
Mr Hyett attested to the Inquiry that, although more detailed
information of the cladding’s behaviour in relation to fire was
contained at section 6 of the BBA Certificate, the designer’s
acceptance of the ‘Class 0’ designation at face value was
reasonable. However, section 6 of the BBA Certificate was
less clear-cut. It stated that the ‘Class 0’ classification only
applied to specific colours, and that alternative hues would
require testing in line with ADB. Further, section 6.5 stated
that: “For resistance to fire, the performance of a wall
incorporating the product, can only be determined by test
from a suitably accredited laboratory, and is not covered
by this Certificate.” Also, can a designer simply accept a
satisfactory surface spread of flame test result, which points
to compliance with ADB section 12.6, without regard to ADB
sections 12.5, 12.7 and the overarching requirement to
comply with the Building Regulation B4.(1). Surely not!
External wall cladding is a significant cost and design element
of both new build and refurbishment projects. Additionally,
commonly used RIBA appointment contracts usually include
the requirements for architects to exercise reasonable skill,
care, and diligence in the discharge of their services. Whilst
the ‘Architects Code: Standards of Conduct and Practice’,
published by the Architects Registration Board, enshrines
“competence” as an expectation of the profession. As such, it
is arguable that a competent designer, exercising reasonable
skill, care, and diligence, should take more than a cursory
glance at key technical data. So, should inconsistencies in
BBA Certificates, such as those highlighted in the previous
paragraph, prompt further technical probing of products and
materials with manufacturers?
This point aside, there has also been considerable
examination of the flammable polyethylene core sandwiched
between the two sheets of 0.5mm thick aluminium that
make up ACM cladding panels. The ‘Class 0’ rating, stated
in the aforementioned BBA Certificate, only applied to the
aluminium face of the composite panel and not to the plastic
core. So, was it necessary to interrogate the complete makeup of the product prior to specifying it?
In Mr Hyett’s opinion, it was reasonable for designers to
assume that the ‘Class 0’ classification of the Reynobond
ACM applied to the product as a whole, including the core.
Therefore, it was reasonable for designers to specify such
products on high-rise buildings; notwithstanding any
shortcomings in the technical data, where responsibility
rested with manufacturers and/or certifying bodies.
However, section 12.5 of ADB also advises that: “The use of
combustible materials in the cladding system … may present
such a risk [for fire spread] in tall buildings.” This appears
to refer to the system as a whole, suggesting that designers
needed to take a holistic review of cladding systems, which,
it could be argued, would include the make-up of composite
materials, in order to discharge statutory obligations under
the Building Regulations.
There has also been much debate regarding the
nomenclature of the ACM polyethylene core and whether it
falls within the definition of “filler material” under section
12.7 of ADB: “Insulation Materials/Products”, which requires
the materials used to be of limited combustibility. In the
immediate aftermath of the Grenfell fire, the government
was quick to clarify its own position on this matter and wrote
to local authority and housing association chief executives
declaring that: “For the avoidance of doubt; the core (filler)
within an Aluminium Composite Material (ACM) is an
“insulation material/product”, “insulation product”, and/or
“filler material” as referred to in Paragraph 12.7 …”.
Dr. Barbara Lane, a fire engineering expert, disputes this
definition, however. In her own evidence to the Grenfell
Inquiry, Dr. Lane asserted that: “… an ACP [ACM] rainscreen
cladding layer is not an insulation material or product ….
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