Grenfell Tower: the road to ambiguity (part 1)

In my last post, I took issue with the Government’s claim that the building regulations require all elements of the cladding system of high buildings to be of limited combustibility. Table A7 of Approved Document B2 indicates clearly that it is insulation material that is covered by the requirement of paragraph 12.7. Also, if ‘all elements’ were meant, then would it not have been said, in simple terms?

Further confirmation that the Government position is insupportable comes from the two leading commentaries on the building regulations. Both seem to take it for granted that AD B2 12.7 applies to insulation products and material only, as I outline later in this post.

First, however, I examine the origins of the Government’s position. Some time this year, the Centre for Window Cladding and Technology (CWCT) published Technical Note 98 on the ‘Fire Performance of Facades – Guide to the requirements of UK Building Regulations’. They comment that while 12.7 ‘specifically’ refers to ‘insulation materials and filler materials’, the paragraph:

is now being interpreted more generally

For this more general interpretation, the CWCT make reference to the BCA’s (Building Control Alliance’s) Technical Guidance Note (TGN) 18 on the ‘Use of Combustible Cladding Materials on Residential Buildings’, whose first edition was published in June 2014. It has three remarkable features:

1. It recommends that under the individual components’ route to compliance, ‘all elements of the cladding system’ should be of limited combustibility (as defined in Table A7 of AD B2).
2. It claims that this is also what the Approved Document recommends.
3. For the alternative whole system route to compliance, it purports to introduce Desktop Studies in lieu of actual fire tests. It also gives the impression that the Approved Document allows for ‘assessments’ rather than actual tests.

I take each of these in turn.

1. The bca’s limited combustibility recommendation

The BCA not only refers to ‘all elements’ of the cladding system, but also makes explicit mention of ‘the external facing material’:

the BCA recommends … [t]he use of materials of limited combustibility for all elements … includ[ing] … the external facing material.

Their recommendation is in line with that of the 1999 EFRA Committee, and with the ‘non-combustible’ requirement adopted in Scotland in 2005. ¹

An undated presentation on ‘External Facades on Tall Buildings – Routes to Compliance’ by Steve Evans for the Building Control Alliance gives some indications as to the factors that prompted the issue of BCA TGN 18. ²  Under the heading ‘Risks to Industry’, slide 8 shows the Address Downtown Fire of 31 December 2015:

There had been at least five PE ACM cladding fires in the four years prior to the publication of BCA TGN 18: ³

Wooshin Golden Suites, South Korea (1 October 2010, report with video)

Al Tayer Tower, Dubai (28 April 2012, video)

Mermoz Tower, France (14 May 2012, video)

Saif Belhaza Building, Dubai (6 October 2012, report)

Tamweel Tower, Dubai (18 November 2012, video)

I have previously presented the certification for the Reynobond PE ACM panels that were used at Grenfell Tower. They achieved Euro Class B and therefore complied with the requirements of AD B2 12.6. By 2014, it must have become clear to the building control profession that they were also extremely dangerous. Ed Galea, Director of the Fire Safety Engineering Group at the University of Greenwhich, told the New York Times (19 June 2017) that to use them on a high-rise building was like:

encasing it in kerosene. … It is insanity, pure and simple.

It is easy, therefore, to understand why there was a move to prevent the use of this type of cladding. What I do not understand is why this did not take the form of a simple Amendment to AD B2 12.7 to bring all elements of the external wall construction under the limited combustibility requirement. In my opinion, this should be a major focus of both the enquiry and the police investigation. How are we to explain the continued permission for highly combustible materials to be used on high rise buildings with apparent complete disregard to human life and safety, and in the face of common sense and expert warnings?

Instead, the new guidance came from the BCA, which has at its core the two organisations, the LABC (Local Authority Building Control) and the ACAI (Association of Consultant Approved Inspectors), which represent the public and private building control sectors respectively. The role of building control, surely, is to interpret and enforce the building regulations, not to reform them by their own decree.

It seems to me possible that it was an awareness of the limits of their proper role that led the BCA to claim that they were not in fact proposing a change in the regulations, but simply explaining them in a new way.

2. The bca’s new interpretation of ad b2 12.7

According to BCA TGN 18, Approved Document B2 recommends for the ‘Linear’ (individual components) route to compliance:

the use of materials of limited combustibility for all key components

It doesn’t. It specifies that insulation material should be of limited combustibility. It may be that non-insulating filler materials are also meant to be covered by the requirement, but rain screen cladding panels are definitely not included, in my opinion. Here is AD B2 12.7 once again:

and here is Row 8 of AD B2 Table A7:

In ‘The Architect in Practice’ (Wiley-Blackwell, 2010) the authors directed (p. 242) members of their profession to two leading commentaries on the Approved Documents:

Knight’s Guide

Knight’s Guide to Building Control Law and Regulations is a five-volume loose-leaf title updated five times a year, and running to 12,000 pages according to Amazon. The publisher states that its principle aim is to provide:

the legal background to, and authoritative commentary on, the current Building Regulations in England and Wales, the Approved Documents, and the Approved Inspector Regulations.

One feels that its commentary probably carries a certain weight if buyers are to be found for it at £996.00 from the publisher. For B4 and Section 12 it reads as follows:

At 7.144, Knight’s Guide makes reference to changes introduced in the 2006 edition of AD B2. In the previous edition (2000 with amendments of 2000 and 2002), the equivalent restriction (13.7, part) had read:

In place of ‘insulation material used in ventilation cavities’ came, in 2006, ‘insulation product, filler material … etc’. Knight’s Guide describes this change as:

additional guidance on insulation materials

It does not understand the revision to be extending the restriction beyond insulation materials to other elements of the external wall construction.

‘The building regulations: explained and illustrated’

The 14th edition of ‘The Building Regulations: Explained and Illustrated’ was published earlier this year:

Reference is made to rain screen cladding. The surfaces of the outer cladding should comply with the requirements of what is 12.6 in AD B2 and, according to the book, ‘any insulation used in ventilated cavities in the external walls of a building over 18 m in height should be of limited combustibility’:

It would appear that the limitation to usage in ventilated cavities has been carried over inadvertently from an earlier edition. Table 7.8 gives the requirement for the ‘surface of the outer cladding which faces the cavity’:

The requirement for heights buildings over 18 m and more than 1 m from any adjacent building is given in the right hand corner as Class 0. This is inaccurate as AD B2 allows Euro Class B as an alternative to Class 0. But the principle is the same. For the outer cladding, Class 0 is presented in the book as the relevant fire rating.

Despite the apparent errors, the point may still be taken that this leading commentary makes no reference to any limited combustibility requirement for the external wall construction for any elements other than insulation material. Any major extension beyond insulation would surely have come to the attention of the authors.

CWCT Technical Note 73, March 2011

The CWCT’s Technical Note 98, referred to above, states that it supersedes TN 73:

The earlier note, (now removed upon request from CWCT) on ‘Fire performance of curtain walls and rainscreens’ was published in March 2011. It understood the limited combustibility requirement to apply only to insulation and filler materials, with the same various exceptions that are specified in AD B2 12.7.

(The statement about Scotland appears to be in error, since there all elements of the cladding system had been required to be ‘non-combustible’ since 2005.)

It would appear then that the more general interpretation referred to in CWCT TN 98 (2017) was unknown to the CWCT at the time of CWCT TN 73 (2011).

effect of the new advice and ‘interpretation’

I would expect that virtually all building control professionals would have at least some awareness of new advice or interpretations contained in the BCA’s Technical Guidance Notes. The same may not be true of designers and contractors, many of whom may consider it sufficient to be cognisant of the content of the Approved Documents.

To the extent that designers and contractors became aware of the new advice and interpretation in BCA TGN 18, it seems likely that the effect was to encourage a shift away from the use of combustible cladding in high rise buildings. No doubt the shift was already underway because of the recent facade fires.

The question then arises as to what happened when a designer or contractor specified combustible outer cladding which had a national Class 0 or Euro Class B surface rating, and was therefore in compliance with the Approved Documents. What would be the response of a Building Control official or Approved Inspector who knew the new BCA guidance? It seems to me that while they might advise against the use of the cladding, it would be hard for them to refuse a design that was in compliance with the Government’s guidance.

It may perhaps be that we ended up with the worst of both worlds. On the one hand, the effect of a partial shift towards non-combustible outer cladding could have been to lessen the pressure for a change in the regulations. On the other, the door may have remained open for the less careful and conscientious designers and contractors to continue to specify and employ combustible materials.

As for the new ‘interpretation’ of AD B2 12.7, the effect must surely have been to create a degree of confusion and an atmosphere of vagueness about the meaning of a text that had previously been understood clearly enough.

[Continued in Part 2.]