Faculty of law blogs / UNIVERSITY OF OXFORD

Cladding: combustibility, terminology and Building Regulations

This blogpost discusses legal and technical issues concerning cladding following Grenfell and some areas of current dispute. The post cannot be relied upon and specific advice should be taken on any of the issues raised in the summary below. No assumption of responsibility is therefore made. James Bessey is Partner of Blake Morgan LLP.


James Bessey


Time to read

5 Minutes

One of the key questions following Grenfell is whether the insulation and cladding on tall buildings complies with Building Regulations. The Regulatory Landscape is complex.  The Building Act 1984 generates the power to make Building Regulations, and approve documents giving practical guidance. Under the Building Regulations 2010, functional standards are set out in Schedule 1: part B4 deals with external fire spread: "the external walls of a building shall adequately resist the spread of fire over the walls and from one building to another, having regard to the height, use and position of the building".

The issue is what "shall adequately" means.

Approved Document B (ADB) provides the practical guidance (but there are alternative routes to compliance, such as the BCA).

ADB 12.5 sets the scene: “The external envelope of a building should not provide a medium for fire spread if it is likely to be a risk to health or safety”, but then continues: “The use of combustible materials in the cladding system and extensive cavities may present such a risk in tall buildings.”

Paragraph 12.5, ADB, states external walls should either:

  1. meet the guidance given in ADB 12.6 to 12.9; or
  2. meet the performance criteria given in the BRE Report Fire performance of external thermal insulation for walls of multi storey buildings (BR 135) for cladding systems using full scale test data from BS 8414-1: 2002 or BS 8414-2: 2005.

BS 8414 tests are discussed below.

The BS8414 test in action: cladding ready to be tested for fire spread and combustibility

James Bessey/Blake Morgan LLP


ADB 12.6 concerns fire surface spread, and ADB 12.7 concerns combustibility. The focus is on buildings over 18m tall, an historical anomaly relating to the (then) maximum firefighting access, but it is the current benchmark. (The recent Hackitt report used a 10-storey description, perhaps unhelpfully introducing another parameter. It is unclear which standard will be used after the current inquiry.)

ADB 12.7 says “In a building with a storey 18m or more … any insulation product, filler material (not including gaskets, sealants and similar) etc. used in the external wall construction should be of limited combustibility".

Grenfell, and many other buildings, used "PE" ACM cladding panels. ACM means Aluminium Composite Materials – a sandwich construction consisting of two outer layers (normally aluminium) with a central core or filler. PE is the industry abbreviation for Polyethylene, the core between the outer layers (Reynobond PE is what was used on Grenfell). Underneath the cladding, is the insulation. In June 2017 the DCLG made clear that the core filler comes within ADB 12.7. Although some contractors have suggested this statement represented a change in requirements or interpretation, the government statement simply confirms the existing state of things.

A further argument now being seen is to allege that the heading to ADB 12.7 (Insulation Materials/Products) limits that paragraph to insulation materials only, and the filler in ACM is not insulation. Such a defence seems problematic for at least three reasons. First, as a general proposition of law, headings are not taken into account when interpreting the words used in the obligation. Second, the whole point of amendments made in 2006 to the earlier Building Regulations 2000 was specifically to identify filler material in addition to insulation materials (and both terms are used in 12.7). Third, such a narrow argument as to 12.7 both overlooks the terms used in ADB 12.5 and the wording of B4(1) itself.

The BS8414 Test:

Putting out the BS8414 test fire

James Bessey/Blake Morgan LLP


The BS8414 test has been heavily used by commercial parties and Government to test cladding since the disaster. It evaluates whether a cladding system resists excessive fire spread based on tests of an 8m high section of walling. The majority of tests have been failed. All PE (Polyethylene) panels that are not ‘Fire Retardant’ (FR) have failed. Much FR is PE treated with a retardant and only in very limited/rare circumstances has FR cladding passed (dependant on insulation used).

Each individual scenario needs to be assessed as to whether failure is likely given these results and/or whether a specific test is required. The current practical problem is a long wait for tests.

Responsibility to Replace

Health and Safety obligations cause two initial questions to be asked: is there power to stop people occupying, and who has power to put the cladding right? A large number of laws may be relevant:

  • rights and obligations under both commercial and residential leases;
  • the Fire Safety: Regulatory Reform (Fire Safety) Order 2005 (with an obligation to conduct Fire Safety Risk Assessments);
  • duties owed to employees and visitors / users (e.g. the Management of Health and Safety at Work Regulations 1999; the Statutory duty to take reasonable care to ensure visitors reasonably safe (Occupiers’ Liability Acts) and the Corporate Manslaughter Act 2007;
  • the Defective Premises Act 1972 which concerns residential building standards.

Recovery Claims

Claims may be brought to recover the cost of replacing cladding.

After the BS8414 test: how the cladding performed

James Bessey/Blake Morgan LLP


In commercial scenarios likely defendants include the Main Contractor, Specialist, Design Consultant and/or the Fire Consultant. Such claims can be brought either in direct Contract or under Warranty Deed.

In residential scenarios, there is often no direct cause of action against the Builder/Contractor or the original developer. Claims are more likely to be made under defect Insurance policies such as NHBC, Zurich, CRL etc. Issues have developed about whether there is liability under these policies. A typical argument is that there is no "damage", i.e. the cladding is not damaged itself and/or is not damaging the building. Whether this really works as a defence remains to be tested in Court.

It is worth noting that Local Authorities are generally not liable for Building Regulation/certificate issues (this is a well-established case law based principle).

In principle, liability might exist by reference to the following requirements:

  1. to meet statutory obligations;
  2. for design;
  3. for the selection of materials;
  4. for workmanship.

A PI (Professional Indemnity) insurance is only likely to respond in respect of the specified design obligations. The design relates to a duty of care to take reasonable skill and care (cf. more absolute contractual duties to meet statutory obligations, relevant British Standards or workmanship).

Other potential issues are Certifier Liability and Manufacturer / Product Liability.

Where do we go from here?

Following the tragedy at Grenfell Tower, we have had two reports from Dame Hackitt, Interim and Final. The public Inquiry is ongoing.

We can expect large-scale industry changes, in the commercial sector at least, driven by (future) tenants/end-users and/or insurers. These pressures are likely to drive change almost regardless of the 18m distinction because of the risk of being left with a less marketable building. There is continuing questioning of both insulation materials (their test results and the testing methods) and of fire door ratings. Other cladding materials beyond ACM are coming up for scrutiny. There are also issues around fire stopping and the impact of alterations to and maintenance of buildings.

A conflict persists between the complexity of regulation, the need for clarity and the ever more complex buildings which are being built. In 2017 DCLG commissioned NBS Research published in April 2017, just 6 weeks before the Grenfell fire, which concluded that professional users find approved documents unnecessarily complex; especially ADB. The NBS report ends with a quotation from a Building Control Officer:

“The building regulations are becoming far too complex and scientific. They should be straight to the point so that everyone from the designer to the builder and the end user can understand them and implement them. There is no point in having a group of academics and scientists write the documents when nobody else understands them or have five different interpretations of what they actually mean and then expect somebody to build it on site. Go back to basics, minimum requirements with clear text and diagrams. There is an industry out there trying to untangle what the documents mean and what they should be complying with.”

The Grenfell enquiry will not be the first criticism of ADB. Her Honour Frances Kirkham CBE Coroner’s Rule 43 letter on the Lakanal House fire stated:

“…Approved Document B is a most difficult document to use. Further, it is necessary to refer to additional documents in order to find an answer to relatively straightforward questions concerning the fire protection properties of materials to be incorporated into the fabric of a building".

It now remains to be seen how the Hackitt report conclusions are implemented. In the meantime, both commercial occupiers and residential owners are struggling with the consequences of the use of ACM cladding products.


How to cite this blog post (Harvard style) 

Bessey, J. (2018). ­Cladding: combustibility, terminology and Building Regulations. Available at: https://www.law.ox.ac.uk/housing-after-grenfell/blog/2018/09/cladding-combustibility-terminology-and-building-regulations (Accessed [date]).