Last edited 11 Feb 2021

ACM cladding




The term 'cladding' refers to components that are attached to the primary structure of a building to form non-structural, external surfaces. This is as opposed to buildings in which the external surfaces are formed by structural elements, such as masonry walls.

Aluminium Composite Material (ACM) panels are commonly used for cladding buildings, typically as a form of rainscreen. A rainscreen (sometimes referred to as a ‘drained and ventilated’ or ‘pressure-equalised’ façade) is part of a double-wall construction. The rainscreen itself simply prevents significant amounts of water from penetrating into the wall construction. Thermal insulation, airtightness and structural stability are provided by the second, inner part of the wall construction.

ACM cladding consist of two skins of aluminium bonded to either side of a lightweight core of materials such as polyethylene (PE), polyurethane (PUR), profiled metal or a mineral core. It is a popular product because of its precise flatness, variety of surface finishes and colours, light weight and formability. However, during a fire, the panels can delaminate, exposing the core material.

Grenfell Tower fire

ACM cladding became notorious following the Grenfell Tower fire on 14 June 2017, when ACM cladding with a polyethylene core was thought to have contributed to the rapid spread of the fire up the outside of the tower. The Reynobond PE ACM cladding used was reported by the press as being a ‘cheaper, more flammable’ option, compared to Reynobond FR, which has a fire-retardant core, or Reynobond A2 which has a non-combustible core.

ACM cladding was also linked to the Lakanal House fire in Camberwell (2009), the Wooshin Golden Suites fire in Busan (2010), the Lacrosse Tower fire in Melbourne (2014), and the Marina Torch and the Address Downtown fires in Dubai (both in 2015).

The Guardian reported that German construction companies have been ‘banned’ from using 'plastic-filled' cladding on towers more than 22 m high since the 1980s and that US building codes restrict the use of metal-composite panels without flame-retardant cores on buildings more than 15 m high.


Speaking on 19 June 2017, Chancellor Philip Hammond said; "My understanding is that the cladding in question, the flammable cladding which is banned in Europe and the United States, is also banned here..." It is not entirely clear what Hammond meant by this. He went on to suggest that; “There are two separate questions. One is: are our regulations correct? Do they permit the right kind of materials and ban the wrong kind of materials? The second question is: were they correctly complied with?"

John Cowley, managing director of CEP Architectural Facades, producer of rainscreen panels for the cladding sub-contractor Harley Facades Ltd, said:

“Reynobond PE is not banned in the UK. Current building regulations allow its use in both low-rise and high-rise structures… The key question now is whether the overall design of the building's complete exterior was properly tested and subsequently signed off by the relevant authorities including the fire officer, building compliance officer and architect before commencement of the project.”

Building regulations

In England, the building regulations establish requirements for specific aspects of building design and construction. Approved documents then provide guidance for satisfying those requirements in common building situations.

The potential for a fire in a multi-storey building to break out through the facade and then to rapidly spread across external cladding is addressed in approved document B. This states that ‘The external envelope of a building should not provide a medium for fire spread if it is likely to be a risk to health and safety. The use of combustible materials in the cladding system and extensive cavities may present such a risk in tall buildings.’

Limited combustibility can be demonstrated in two ways:

NB: On 28 July 2017, following the Grenfell fire, then-Communities Secretary Sajid Javid announced an independent review of the building regulations and fire safety. See: Independent review of the building regulations and fire safety.


On 18 June 2017, the government required social housing owners to compile lists of buildings with ACM cladding and buildings more than 18 m high and then to send samples of the cladding for fire tests.

The letter from Melanie Dawes, Permanent Secretary for the Department for Communities and Local Government (DCLG) (File:Acm cladding checks.pdf), gave the following advice on the identification of ACM cladding.

Aluminium Composite Material (ACM) is a type of flat panel that consists of two thin aluminium sheets bonded to a non-aluminium core, typically between 3 and 7 mm thick. The panels can have a painted or metallic finish (e.g. copper or zinc effects). It can be differentiated from solid aluminium sheet by looking at a cut edge whereby the lamination is visible. It may be necessary to cut a hole in a panel if a cut edge is not readily accessible.

The Annex suggests that:

On buildings with a floor over 18 m above ground level, where ACM panels are identified, it is necessary to establish whether the panels are of a type that complies with the Building Regulations guidance, i.e. the core material should be a material of limited combustibility or Class A2. Material of limited combustibility as described in Table A7 of Approved Document B (Vol 2) Class A2-s3,d2 or better in accordance with BS EN 13501-1.

On 21 June 2017, Melanie Dawes wrote a similar letter to owners, landlords and managers of private residential blocks offering testing of ACM cladding, paid for by DCLG. (Ref.

On 23 June 2017, the Police confirmed that small-scale fire tests had been carried out on the Reynobond ACM cladding and the Celotex insulation used on Grenfell Tower, and both had failed. However, Detective Superintendent Fiona McCormack said; "The insulation was more flammable than the cladding. Tests show the insulation samples combusted soon after the test started."

See also: Celotex RS5000 PIR insulation.

On 24 June 2017, the government issued a statement from Sajid Javid, the then-Secretary of State at Department for Communities and Local Government (DCLG) regarding the cladding testing failure rate. It confirmed that all the cladding samples tested, that is, samples from 34 high-rise buildings in 17 local authority areas, had failed a combustibility test carried out by the Building Research Establishment (BRE). Fire and rescue services were asked to conduct fire safety inspections of those buildings to decide what remedial works might be required.

However, the statement made clear that:

...a failure in testing of the cladding does not necessarily mean that a building will have to be evacuated; the decision by Camden Council to evacuate 4 of the 5 towers on the Chalcots Estate was because the failed testing of the external cladding was compounded by multiple other fire safety failures which the fire inspection team found within the buildings.


On 24 June 2017, Reuters reported guidance set out in a 2016 Reynobond brochure, which stated that 'as soon as the building is higher than the fire fighters’ ladders, it has to be conceived with an incombustible material.' However, the Reuters article suggests that Arconic, the US company that supplied the cladding panels for Grenfell Tower may have known that it was a tall building when bidding for the project in 2014.


On 26 June 2017, Arconic announced that it was discontinuing sales of Reynobond PE for use in tower blocks, saying 'we believe this is the right decision because of the inconsistency of building codes across the world and issues that have arisen in the wake of the Grenfell Tower tragedy regarding code compliance of cladding systems in the context of buildings’ overall designs.'

On 26 June 2017, in a statement to the House of Commons, Sajid Javid announced the creation of the Grenfell Tower independent expert advisory panel to advise the government on the fire.

By 27 June 2017, 75 cladding samples had 'failed' the fire tests being undertaken - 100%. Fire safety experts then began to question what sort of testing was being carried out, pointing out that it is the entire cladding assembly that needs to be tested, not just small samples, and suggesting the building regulations do not require that cladding panels achieve a Class A2 rating if the entire cladding system meets the standards set out in BS 8414. Concern was also expressed that removing cladding from buildings could compromise any insulation that was exposed.

On 28 June 2017, with 120 cladding samples having 'failed' tests, the National Housing Federation chief executive David Orr suggested the tests should be stopped, and the focus shifted to considering how to make people feel safe in their homes.

On 29 June 2017, Theresa May announced that Sir Martin Moore-Bick had been appointed to lead a Public Inquiry into the fire. For more information, see Grenfell Tower Inquiry.

On 30 June 2017, the BBC and the Times reported having seen documents showing that the original cladding specified for the Tower had been a zinc cladding with a fire-retardant core, but in 2014 this was changed to ACM cladding with a PE core to save £293,000 and to allow a change of colour. However, the BBC point out that ‘both types of cladding have the same official fire rating’ (it is not clear what is meant by the word ‘official’) and there was ‘no suggestion a deliberate decision was made to cut fire safety’.

(Ref. and

By 2 July 2017, DCLG were reporting that 181 samples of cladding had 'failed' fire tests - 100% of those tested.

In a statement to the House of Commons on 3 July 2017, Sajid Javid said:

...we ourselves have asked questions about the testing regime after discovering the 100% failure rate so far. Last week I asked for the testing regime to be independently assessed.

This was carried out by the Research Institutes of Sweden, and they have confirmed they believe the process to be sound.

A full explanatory briefing note on the testing process is available on GOV.UK.

As the note explains, every failed test means the panels are unlikely to be compliant with the limited combustibility requirement of the building regulations guidance.

This has been confirmed by legal advice and the advice of the independent expert panel that was established last week.

For use of the panels to be safe landlords need to be confident that the whole wall system has been tested and shown to be safe.

We are not aware of any such system having passed the necessary tests, but I have asked the expert advisory panel to look into this further.


The Government building safety programme - explanatory note referred to in the statement says:

The Department’s view, supported by expert and legal advice, is that external walls in a tower block can meet the Building Regulations requirement for resisting fire spread in two ways....

The tests being conducted at BRE are testing only whether the core or filler of ACM panel samples being submitted are of a type that would fail the limited combustibility test for an individual element of a wall in a tall building (the first of the requirements summarised above).

It is possible, therefore, that ACM panels that have a core material that is not of limited combustibility, might be safe if installed as part of a whole wall system that meets the second test described above.

See also: ACM cladding testing by BRE.

At the third meeting of the Independent Expert Advisory Panel, they suggested drawing attention to the need to ensure recladding work complies with all Building Regulations’ requirements, including; structural safety, resistance to moisture penetration and build up, and energy - as well as ensuring fire safety. As a result, on 13 July 2017, a letter was sent from the Department for Communities and Local Government (DCLG) to all building control bodies in England including approved Inspectors.


Further tests

On 6 July 2017, the Grenfell Tower independent expert advisory panel advised that further testing should be carried out by BRE to establish how different types of ACM cladding behave in a fire in combination with different types of insulation. This, they suggested would help landlords decide what further measures may be needed to make their buildings safe.

The tests were expected to look at six combinations of three different types of ACM cladding, with polyethylene, fire retardant polyethylene, and non-combustible mineral cores, combined with insulation of rigid polyisocyanurate foam and non-combustible mineral wool. The tests, carried out in accordance with BS 8414, involve building complete cladding systems 9 m tall and then subjecting them to a severe fire.


Following this announcement, two housing associations in Salford stopped cladding removal work on a number of tower blocks. Executive director of operations at Salix Homes, Sue Sutton said " ...advice regarding the removal of cladding is now unclear and there is conflicting information about the need to remove the panels."

Then-Communities Secretary Sajid Javid made an oral statement to Parliament on 20 July 2017, giving an update on the government response to the fire. He said that:

" more than 208 local authority and housing association residential blocks over 18 metres tall have been fitted with aluminium composite material cladding. 189 of these have had cladding samples tested by the Building Research Establishment, they’ve been tested by proxy or they have already had taken their cladding down. None of them have passed the limited combustibility test."


DCMS also published an explanatory note on the large-scale testing. (File:20170720 Explanatory note on large scale testing FINAL.pdf.) The testing cycle is around eight days for each wall - including construction, setting up and undertaking the test, and deconstructing the wall.

24 July 2017 ACM with unmodified polyethylene filler with PIR foam insulation
31 July 2017 ACM with unmodified polyethylene filler with mineral wool insulation
ACM with a fire retardant polyethylene filler with PIR foam insulation
7 August 2017 ACM with a fire retardant polyethylene filler with mineral wool insulation
14 August 2017 ACM with a limited combustibility filler with PIR foam insulation
ACM with a limited combustibility filler with mineral wool insulation

However, the tests are only illustrative of how different systems might behave. Building owners will still need to take their own professional advice on what steps to take depending on the materials they have on their buildings.

The first results of the tests were revealed on 28 July 2017, when DCMS announced that a system comprising ACM cladding with polyethylene filler (Category 3) and foam insulation, with fire breaks and cavity barriers in place did not satisfy the requirements of the building regulations. 82 buildings are thought to have this combination of materials in their wall construction.


Following these results, the government issued further advice for landlords of affected buildings.


On 2 August 2017, the government announced that the second series of tests had been completed, testing a system consisting of ACM cladding with a polyethylene filler (category 3) with stone wool insulation. The Grenfell Tower independent expert advisory panel advised that the combination does not meet current building regulation guidance. There are 111 buildings known to use this system.


On 8 August 2017, results of the third series of tests was published, consisting of ACM cladding with a fire retardant polyethylene filler (category 2 in screening tests) with PIR foam insulation. Again, the Grenfell Tower independent expert advisory panel advised that the combination of materials does not meet current Building Regulations guidance. It was also reported that to further build the evidence available, the government has commissioned a seventh large scale test on ACM cladding with fire retardant polyethylene filler (category 2 in screening tests) with phenolic foam insulation.


On 11 August 2017, the results of the fourth round of tests was published, relating to ACM cladding with a fire resistant polyethylene filler (category 2 in screening tests) and stone wool insulation (a form of mineral wool). The combination of materials passed the test and so can be compliant with the Building Regulations. Following the tests, Advice for building owners: large-scale wall system test 4 was published by the Grenfell Tower independent expert advisory panel.

On 14 August 2017, the results of the fifth test, assessing ACM cladding with a limited combustibility filler (category 1 in screening tests) with PIR foam insulation were published. The Grenfell Tower independent expert advisory panel reported that these results show the combination of materials can comply with the building regulations.


On 21 August 2017, the results of the sixth large scale tests were published, revealing that a system consisting of ACM cladding with a fire retardant polyethylene filler (category 2 in screening tests) with phenolic foam insulation did not satisfy the Building Regulations.


On 25 August, the results of the final test were published, a system consisting of ACM cladding with a limited combustibility filler (category 1 in screening tests) with stone wool insulation. The Grenfell Tower independent expert advisory panel reported that this combination of materials can be compliant with the building regulations when installed and maintained properly.


In a statement to Parliament on 5 September 2017, then-Communities Secretary Sajid Javid confirmed that the cladding systems that passed the tests are in use on eight social housing towers. Systems that failed are in use on 165. He also stated that inspections have highlighted other safety issues related concrete panel systems.


For more information, see ACM cladding testing by BRE.

In February 2018, BRE issued a statement revealing that the original tests they had carried out on the cladding system in 2014 were carried out on a test system that was not constructed according to Celotex’s design specification. The statement said; "The cladding system in that test included Celotex RS5000 and fibre cement board rainscreen (declared reaction to fire classification A2) – this was not an Aluminium Composite Material (ACM), nor was it the cladding system on Grenfell Tower." BRE made clear that they did not design, select or install the test system, and were not involved in the sample selection process.


On 11 December 2017, the Department for Communities and Local Government issued Advice for building owners: external wall systems that do not incorporate ACM. Separate guidance, Advice for building owners: External Wall Insulation (EWI) systems with a render or brick-slip finish, was also published on 11 December.

On 16 May 2018, the government announced it would fully fund the removal and replacement of unsafe cladding by councils and housing associations at an estimated cost of £400 million. Further details will be announced shortly explaining how to apply for this funding, including conditions attached to the grant. Building owners in the private sector must make their own arrangements to ensure they are made safe.


Other developments

February 2018

On 15 February 2018, the UK's largest distributor of high-performance cladding systems called for greater clarity about fire rating standards for ACM cladding.

Birmingham-based Vivalda Group, announced that they had stopped stocking ACM below A2 standard for use on high-rise applications, and warned that given the complexity of the current safety standards, there was a risk of unintentional specification errors. In particular, they pointed to shortcomings in the current approved inspector regime, which they claim has created "a confusing landscape for contractors". The situation is exacerbated by the fact that complex laboratory tests used by manufacturers to obtain approval for cladding systems are impossible to replicate on site.

April 2018

On 11 April 2018, the government announced plans to strengthen fire testing for cladding systems on residential buildings, restricting or banning the use of desktop studies as a way of assessing fire performance. A consultation on the proposals will also consider whether desktop studies are appropriate for any construction products. The consultation ended on 25 May 2018.


June 2018

In June 2018, Communities Secretary James Brokenshire launched a consultation on banning the use of combustible materials in the external walls of high-rise residential buildings.

On 28 June 2018, government figures revealed the total number of high-rise blocks fitted with unsafe ACM cladding was 51% higher than previously thought, at 470. Of these, 297 were private sector blocks, only 21 of which had started remediation. Of the 159 social sector blocks, remediation work had started on 60% and had been completed on 9%. (Ref.

In response to these figures, Brokenshire announced a package of measures to speed up action by building owners. A national remediation programme for the private sector will be overseen by a new taskforce, ensuring that plans are in place for every affected building. In addition, £1m of funding will be provided for councils to increase their inspection capacity.

July 2018

In July 2018, government figures revealed that the number of private sector blocks with ACM cladding systems had risen to 301 from 297. Of these, there are no plans in place to replace the cladding in 224 instances.

Equally worrying, the data, according to the Ministry of Housing, Communities and Local Government's Building Safety Programme, reveals that the government is still unaware of the cladding status of a further 100 private sector blocks, despite enforcement notices being issued to all but a handful of their owners in a bid to obtain construction information.

August 2018

In August 2018, Inside Housing reported that minutes of a meeting held in 2014 appeared to suggest the government had been told it needed to clarify official guidance to ban ACM cladding but that it had failed to act.

In the meeting, held by the Centre for Window and Cladding Technology (CWCT), officials were warned that the guidance was 'not clear'. Approved Document B (ADB) was believed by government officials to ban the use of the flammable ACM through a clause stipulating that 'insulation materials/products' should be of limited combustibility. However, the industry figures present at the meeting rejected this argument, according to the minutes.

The minutes also suggest an agreement to draft clarification to specifically outlaw the material and to prepare 'Frequently Asked Question', but neither were done.

A BRE spokesperson said: “We were part of an ongoing discussion around FAQs for the planning portal with CWCT and other experts. This discussion concluded when the online government consultation re. ADB was launched in February 2016. This was based on the collective view that these issues would best be covered off in the subsequent revision to ADB.”

An MHCLG spokesperson said: “As we have said repeatedly, our view is that the limited combustibility requirements in the guidance cover the core filler of a cladding panel."


September 2018

In September 2018, Communities Secretary James Brokenshire informed around 60 building owners and developers - including some of the biggest property firms such as Lendlease and Pemberstone - that they must take action to remove ACM cladding or face penalties. The warning came as some homeowners in buildings with unsafe cladding face large bills for removal and replacement works because of building owners refusal to pay. Some developers however have already pledged to cover the costs of such work.

Brokenshire said: “There is a moral imperative for private sector landlords to do the right thing and remove unsafe cladding quickly, and not leave leaseholders to cover the cost.” He warned that firms could face fines or be barred from other government schemes if they do not comply.

Later in September 2018, MHCLG's Building Safety Programme reported that the number of private high-rise residential buildings with unsafe cladding and no clear remediation plans had fallen since August but still stood at 124.

The updated figures show that there are 30 private sector residential buildings with a cladding status that is still to be confirmed (down from 60 in August). Of the 159 social sector buildings, 22 have finished remediation works and 99 have started. The remaining 38 have remediation plans in place.

In the private sector, just 10 buildings have completed remediation, while 26 are undergoing such works. Plans are in place for 67 buildings, while there are 68 buildings where remediation plans are being developed.

October 2018

On 1 October 2018, the government confirmed that it would ban the use of combustible materials on the external walls of high-rise residential buildings. The ban is to also apply to hospitals, care homes and student accommodation over 18 m-tall. (Hotels and office buildings are to be exempt due to their different evacuation strategies and lower risks.)

Confirming the ban at the annual Conservative Party conference, Communities Secretary James Brokenshire said that it would be delivered through changes to Building Regulations to be brought forward in late-autumn 2018. It will see to limit materials available for such applications to products that achieve a European classification of Class A1 or A2.

On 17 October 2018, the government announced that they were releasing the first tranche of an estimated £400 million to 12 local authorities and 31 housing associations. The money is intended to cover the costs of removing and replacing ACM cladding from their high-rise social housing buildings.

Although details of which buildings were receiving the funding were withheld, it is understood that most are located in London.

Government signalled that the funding was intended to enable other vital services to continue without impact while the buildings at risk are made safe. The government said they would closely monitor progress and costs which are subject to change.

November 2018

After several months of warnings, the government acted on 29 November 2018 to give councils the authority to strip combustible materials off buildings themselves and reclaim the cost from landlords.The government will provide full backing, including financial support, for local authorities to carry out emergency work on private residential buildings with unsafe ACM cladding.

Meanwhile, the government confirmed the ban on combustible materials on all new residential buildings over 18 m-tall, as announced in October (see above). The ban is to come into effect on 21 December 2018.

The changes to Approved Document B and Approved Document 7 are available at:


In May 2019 the government announced it would fully fund the replacement of unsafe ACM cladding on high-rise private residential properties where building owners have failed to do so. Around £200 million will be made available to remove and replace cladding from around 170 privately-owned high-rise buildings.

Communities Secretary, Rt Hon James Brokenshire MP, said: "Although temporary measures are in place to ensure people living in these buildings are safe, too many owners are treating this as a permanent fix. Others are trying to pass on the costs to residents by threatening them with bills running to thousands of pounds... If these reckless building owners won’t act, the government will."


In June 2019, the Ministry for Housing, Communities and Local Government (MHCLG)’s Building Safety Programme reported that remediation of ACM cladding had been completed on just 7.4% of private high-rise buildings, compared to 35.4% in the social residential sector.

The latest information from the government can be seen at:

In July 2019, the Expert Panel of the Ministry of Housing, Communities and Local Government (MHCLG) reported that HPL panels of Class C or D are very unlikely to adequately resist the spread of fire. In addition, systems using any type of HPL panels (Class B, C or D) with combustible insulation are very unlikely to adequately resist the spread of fire.

For more infomration see: HPL cladding.


On 20 January 2020 Housing Secretary Robert Jenrick announced new measures to improve building safety standards, described as: ‘the biggest change in building safety for a generation’. The changes, include the immediate creation of a new Building Safety Regulator and a consultation on extending the ban on combustible materials. For more information see: Reform of building safety standards.

On 6 March 2020, the Housing, Communities and Local Government Committee announced an inquiry to examine the scale of issues facing residents in buildings due to combustible cladding. It will also look at the quality and effectiveness of Government support for the removal of all form of dangerous cladding from existing buildings, in particular the pace of remediation. Ref:


On 10 February 2020, the Housing Secretary announced the government would pay for the removal of unsafe cladding for all leaseholders in residential buildings of 18 metres (6 storeys) and over in England. Lower-rise buildings, with a lower risk to safety, will also gain new protection with no leaseholder paying more than £50 a month towards the removal of unsafe cladding. Including previous announcements, this represents a £5 billion investment in building safety. A new tax will be introduced for the UK residential property development sector to raise at least £2 billion over a decade to help pay for cladding remediation costs. Ref

Related articles on Designing Buildings Wiki


Why has there not been any discussion on the relevancy of the compliance requirements for manufacturers/importers responsibilities under Construction Products Enforcement Regulations 2013 by MCHLG or the construction industry in regards to the cladding?

You mean the Construction Products Regulations.

The cladding had been tested, the question is whether the tests were appropriate / carried out on the correct product / applied correctly. The supplied test results restricted the use of the cladding to the exact configuration that had been tested and required that further tests be carried out if a different configuration was used.

In February 2018, BRE issued a statement revealing that the original tests they had carried out on the cladding system in 2014 were carried out on a test system that was not constructed according to Celotex’s design specification. See

'This article states that ‘The external envelope of a building should not provide a medium for fire spread if it is likely to be a risk to health and safety. The use of combustible materials in the cladding system and extensive cavities may present such a risk in tall buildings.’ As a result, materials with limited combustibility must be used in buildings with storeys more than 18 m above the ground.'

Does this follow? 12.5 says that combustible materials may present a risk. Then follows specific instructions, with 2 alternative routes to compliance. The Linear Route only specifies that insulation materials and filler materials etc should be of limited combustibility. Why then do you say in effect that the AD B2 requires that all materials be of limited combustibility?


The article has been corrected to reflect this comment.

Designing Buildings Anywhere

Get the Firefox add-on to access 20,000 definitions direct from any website

Find out more Accept cookies and
don't show me this again