Chapter 26: The National House Building Council

Chapter 26: The National House Building Council

NHBC and associated organisations

¶26.1 The National House Building Council (NHBC) is the largest provider of warranties for newly built properties in the UK and (through its subsidiary) the largest private building control body in England and Wales.^16841684 Evans {Day219/17:5}-{Day219/18:17}. NHBC did not provide building control or warranty services for the Grenfell Tower refurbishment, but it had (and retains) a major influence over standards in the housebuilding industry.^16851685 Evans {NHB00003020/13} page 13, paragraph 36(c). Its dealings with Kingspan and DCLG ("the department"), in particular Brian Martin, in the period 2010 to 2016 are revealing.

¶26.2 NHBC was established in 1936 in order to respond to what was seen as the poor quality of construction provided by the housebuilding industry.^16861686 Evans {NHB00003020/4} page 4, paragraph 15. At the time of the Grenfell Tower refurbishment it provided warranties of the quality of construction in the form of its "Buildmark" warranty and building control services as an approved inspector under the Building Act 1984. In both contexts it occupied a dominant position in the private sector market, supplying over 80% of warranties on newly built properties^16871687 {NHB00003501}. and about 60% of the services provided to the residential market by approved inspectors.^16881688 Evans {Day219/18:4-17}.

¶26.3 NHBC is a private company limited by guarantee,^16891689 Evans {NHB00003020/4} page 4, paragraph 15. meaning that it retains any profits it makes rather than distributing them to shareholders.^16901690 Evans {Day219/19:5-25}. Warranties are issued by the company itself, whereas building control services are provided by NHBC Building Control Services Ltd (NHBC BCS), a profit-making company of which NHBC is the sole shareholder.^16911691 Evans {Day219/19:5-25}.

¶26.4 The "Buildmark" warranty is a policy of insurance. Although the standards required for a property to be eligible for a "Buildmark" warranty were set by the Standards department of NHBC, the wording of the policy and its underwriting were handled by a different department.^16921692 Evans {Day225/82:9}-{Day225/83:4}. The issue of warranties was carried out separately from the provision of building control services.^16931693 Evans {NHB00003020/5} page 5, paragraph 18 (b).

¶26.5 Oversight of both warranty and building control operations was provided by NHBC's Technical Services Department; Steve Evans was the Building Control Manager and John Lewis one of the specialist surveyors.^16941694 Evans {NHB00003020/6} page 6, paragraph 18 (c). John Lewis reported to Steve Evans who in turn reported to Diane Marshall in her role as Head of Technical Services. She in her turn reported to Ian Davis, the Operations Director, who was a member of NHBC's board of directors.^16951695 Lewis {NHB00003433/5} page 5, paragraph 18 (c) and {NHB00002769}; Marshall {Day225/79:9-18}. Ms Marshall occasionally reported directly to the board in respect of technical matters and the financial affairs of NHBC BCS.^16961696 Marshall {Day225/79:9-18}.

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¶26.6 The Technical Services Department contained a group set up specifically to deal with projects over eight storeys in height. It was called the Major Projects Team.^16971697 Lewis {Day223/7:9-14}. NHBC did not, however, employ any specialist fire engineers after 2008 and it was not until John Lewis completed a Masters' degree in fire and explosion engineering in 2013 that the teams had access to any internal fire safety expertise.^16981698 Lewis {Day223/5:24}-{Day23/6:20}. Even during that period, Mr Lewis's work was never reviewed by anyone with equivalent qualifications.^16991699 Lewis {Day223/7:5-8}. Mr Lewis was joined by another fire engineer, Maulik Katkoria, in 2016.^17001700 Lewis {Day223/6:21}-{Day223/7:1}.

The Building Control Alliance

¶26.7 The Building Control Alliance (BCA) was formed in 2008 with five member organisations, the Association of Consultant Approved Inspectors (ACAI), Local Authority Building Control (LABC), the Royal Institution of Chartered Surveyors (RICS), the Chartered Institute of Building (CIB) and the Chartered Association of Building Engineers (CABE).^17011701 Evans {NHB00003020/59} page 59, paragraph 164 (b). The alliance was established to promote the role of building control bodies, respond to government proposals, provide mediation services and provide a unified view on areas of uncertainty in the Building Regulations. It was, at least in part, a response to a government review of building control and opposition from building control bodies to a proposed relaxation of building control requirements.^17021702 Evans {Day219/38:15}-{Day219/40:5}; Turner {LABC0011202/28} page 28, paragraph 92. It was later incorporated as a limited company.^17031703 Evans {NHB00003020/59} page 59, paragraph 164 (f). Although the BCA published guidance for the construction industry, it had no statutory standing and was an unregulated, voluntary, professional body.^17041704 Evans {Day219/53:14}-{Day219/55:4}.

¶26.8 NHBC was not itself a member of the BCA, but it was a member of the ACAI, through which it was actively involved in the BCA.^17051705 Evans {Day219/41:22}-{Day219/42:12}. Steve Evans was a founding member of the BCA executive board and was chair of the Technical Group from 2010 until 2019.^17061706 Evans {NHB00003020/60} page 60, paragraph 166-167. He was involved in publishing guidance notes, including Technical Guidance Note 18 first published in June 2014.^17071707 Evans {NHB00003020/61} page 61, paragraph 168. Diane Marshall was a member of the BCA's executive committee from its inception in 2007.^17081708 Marshall {NHB00003434/4} page 4, paragraph 16; Marshall {Day225/86:4-7}.

NHBC's knowledge of Kingspan K15: 2010

¶26.9 By 2010 at the latest, NHBC was aware that combustible insulation was commonly being used in the external walls of buildings over 18 metres in height. In April of that year BRE published a report entitled Fire performance of highly insulated residential buildings and modern methods of construction: A literature review^17091709 {NHB00000452}. that had been commissioned by NHBC Foundation, a body established and funded by NHBC to carry out research and provide guidance to the house-building industry. During the preparation of the report, BRE consulted a group of industry professionals that included two representatives of NHBC, John Lewis and Dave White.^17101710 {NHB00000452/6}. Mr Lewis confirmed that he had read the report at around the time of its publication.^17111711 Lewis {Day223/17:8}.

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¶26.10 The report contained a detailed explanation of the principal regulatory requirements applicable to residential buildings and the materials that were commonly used to construct them. It warned that the growing prevalence of modern insulation products meant that the fire load within dwellings had increased leading to a greater risk of fire spreading through the fabric of the building.^17121712 {NHB00000452/5}. It concluded that the materials being used in the construction of modern buildings appeared to be resulting in increasingly large fire losses.^17131713 {NHB00000452/9}.

¶26.11 Mr Lewis accepted that by April 2010 at the latest he had been aware that combustible insulation was being used much more commonly in the external walls of buildings over 18 metres in height^17141714 Lewis {Day223/19:5-7}. and that the most commonly used product was Kingspan K15.^17151715 Lewis {NHB00003433/7} page 7, paragraph 26. He said that Kingspan K15 was commonly accepted by fire engineers on the basis of its BBA certificate and that NHBC relied heavily on Kingspan's own assurances concerning the way in which its products could be used.^17161716 Lewis {NHB00003433/7} page 7, paragraph 26; Lewis {Day223/22:21}-{Day223/23:20}. For her part, Diane Marshall said that it had been NHBC's practice until 2015 to allow the use of Kingspan K15 on buildings over 18 metres in height, again on the basis of the BBA certificate.^17171717 Marshall {NHB00003434/17} page 17, paragraph 72.

The BBA certificate

¶26.12 The first BBA certificate for Kingspan K15 was issued on 27 October 2008. It referred to one successful test in accordance with BS 8414 Part 1 in 2005.^17181718 {BBA00000038/5}. It stated that Kingspan K15 might be used in accordance with paragraphs 12.5 and 12.6 of Approved Document B,^17191719 {BBA00000038/5-6}. but warned that advice should be sought from the certificate holder if the product were being considered for use on buildings over 18 metres in height.^17201720 {BBA00000038/6}. That statement remained in the version of the BBA certificate that was amended in April 2010 and published in July 2013.^17211721 {BBA00000037/5}.

¶26.13 Seeking advice from the manufacturer in that way was not a route to compliance with the functional requirement of the Building Regulations indicated by Approved Document B. Kingspan could never have given any advice sufficient to satisfy the guidance in Approved Document B or the requirements of the Building Regulations other than that the system proposed for use was or was not the same as that which had been the subject of the 2005 test.^17221722 Lewis {Day223/152:1-19}. It should have been obvious to any properly informed reader of the BBA certificate that Kingspan's own advice could not safely be relied upon.

¶26.14 Nonetheless, NHBC did exactly that. Steve Evans told us that NHBC had been satisfied with a letter from Kingspan's technical department stating that the proposed system was acceptable without knowing anything about the knowledge or experience of the writer and without any guidance from NHBC about what technical information it should contain.^17231723 Evans {Day219/126:19}-{Day219/135:5}. He told us that it was for the NHBC surveyor receiving the letter to decide whether it contained enough information to enable him to approve the use of K15 on a building over 18 metres in height.^17241724 Evans {Day219/133:12}-{Day219/134:1}.

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¶26.15 Diane Marshall sought to justify NHBC's reliance on assurances by Kingspan by referring back to the BBA certificate itself.^17251725 Marshall {Day225/155:3}-{Day225/158:22}. She appeared to think that the effect of the recommendation that advice should be sought from the certificate holder was effectively to enable Kingspan to certify that its products could be used in applications which bore no relation to that on which the BBA certificate was based.

¶26.16 If that was her belief it overlooked two matters of fundamental importance: first, that reliance on the advice of the manufacturer of a product could never have been a proper way of ensuring compliance with the Building Regulations, and secondly, as Ms Marshall accepted, the advice Kingspan provided was generally no more than a bald assertion that K15 was suitable for the project, without any technical assessment or analysis.^17261726 See for example the Kingspan letter of 13 January 2014 to Mount Anvil in respect of its Eagle House project {KIN00002663}; Marshall {Day225/155:3-6}.

Paragraph 12.7 of Approved Document B

¶26.17 When it was revised in July 2013, the BBA certificate included a new statement that Kingspan K15 could be used in accordance with paragraph 12.7 of Approved Document B, which required insulation products used in buildings over 18 metres in height to be materials of limited combustibility.^17271727 {BBA00000037/5}. K15 was not a material of limited combustibility and the reference to paragraph 12.7 was therefore clearly wrong. That mistake should have been obvious to all at NHBC who knew, or should have known, that it was a phenolic foam and therefore combustible.^17281728 Marshall {Day225/115:15}-{Day225/116:11}; Evans {Day219/66:1-4}; Lewis {Day223/37:1-4}.

¶26.18 Despite that, no one at NHBC said anything to the BBA about the error in the certificate until July 2015. The witnesses from whom we heard sought to justify that omission by relying on the Approved Document providing guidance on regulation 7 of the Building Regulations 2010.^17291729 {INQ00014930}. Paragraph 1.15 of that document stated that an independent product certification scheme might indicate that a material is suitable for its intended purpose and use, but the operative word there is "might".^17301730 {INQ00014930/13}. Paragraph 1.18 stated that past experience, such as use in an existing building might show that a product could perform the function for which it was intended, but again, the operative word is "might".^17311731 {INQ00014930/14}. Neither of those paragraphs detracts from the clear requirements of functional requirement B4(1) and the guidance in Approved Document B. If those at NHBC thought they did, they were wrong. Diane Marshall ultimately accepted that the guidance in the Approved Document on regulation 7 could have no bearing on paragraph 12.7 of Approved Document B but she insisted that it provided an alternative route to compliance with functional requirement B4(1).^17321732 Marshall {Day225/101:4-7}.

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¶26.19 In support of that position, Ms Marshall appeared to rely on a section in Approved Document B entitled "Use of Guidance", which stated that building control bodies might accept the certification of products under approved product certification schemes as evidence that they complied with a relevant standard.^17331733 {CLG00000224/7}. She appeared to think that a building control body need look no further than, for example, a BBA certificate, nor examine its contents critically, when deciding whether a product was suitable for use, even when some of the statements in it were obviously wrong.^17341734 Marshall {Day225/114:1}-{Day225/120:13}. We cannot agree. It should have been clear to everyone at NHBC that there was nothing in regulation 7 or Approved Document B that could justify such a perverse outcome. We read regulation 7 and that paragraph in Approved Document B as saying no more than that ordinarily a building control body should be able to rely on statements in certificates issued by certification bodies accredited by UKAS, but not that they are entitled to do so in the face of ambiguity or obvious error.

Internal discussions about K15: August to November 2013

¶26.20 On 28 August 2013, Steve Cook (NHBC's Area Technical Manager for London) wrote to Steve Evans saying that the question of using what he referred to as "non-combustible cavity insulation" in buildings with a storey over 18 metres in height was causing a lot of concern to customers.^17351735 {NHB00000583}. He asked whether NHBC was in possession of any guidance on the issue or whether it might be able to encourage Kingspan to test its K15 and K12 products to achieve certification as non-combustible. Steve Evans replied that NHBC had no involvement in the testing carried out by Kingspan, but that he would discuss with John Lewis whether NHBC might be able to draft some guidance.^17361736 {NHB00000583}.

¶26.21 Mr Cook may have used the phrase "non-combustible" as shorthand for having limited combustibility, or perhaps he did not understand the difference. Either way, Mr Lewis and Mr Evans both told us that they knew at the time those emails were exchanged that Kingspan K15 was combustible and should not be used in the external walls of buildings above 18 metres in height.^17371737 Evans {Day219/65:1-4}; Lewis {Day223/36:15}-{Day223/37:4}. However, neither of them could recall having discussed the matter or reaching any consensus on NHBC's approach to Kingspan K15 at that time.^17381738 Evans {Day219/71:15}-{Day219/72:3}; Lewis {Day223/40:20}-{Day223/41:5}. Certainly, no new guidance was issued.

¶26.22 On 16 October 2013, John Lewis and Steve Cook received an email from a project surveyor in NHBC's Technical Services department. The surveyor said, in summary, that he did not think that Kingspan K15 was a material of limited combustibility but had become aware of a colleague in NHBC who believed that it was and had consequently been accepting its use on buildings above 18 metres in height.^17391739 {NHB00000587}. Mr Cook responded the following day, saying that any insulation used on high-rise buildings was required to be a material of limited combustibility but that Kingspan did not have test evidence to show that K15 met that requirement.^17401740 {NHB00000587}.

¶26.23 Although John Lewis claimed that those emails indicated confusion about whether Kingspan K15 was acceptable for use on high-rise buildings, both he and Steve Evans conceded that they had known that paragraph 12.7 of Approved Document B advised that insulation materials should be of limited combustibility and that Kingspan K15 did not meet that guidance.^17411741 Lewis {Day223/45:4-9}; Evans {Day219/81:2-13}. Nonetheless, NHBC was routinely accepting it for use on high-rise buildings.^17421742 {NHB00000587/2}; Evans {Day219/78:1}-{Day219/82:12}; Lewis {Day223/46:14}-{Day223/47:7} John Lewis sought to justify that approach, again by reference to regulation 7 of the Building Regulations. He conceded, however, that he had never checked whether regulation 7 supported NHBC's approach and could not recall anyone else at NHBC having done so.^17431743 Lewis {Day223/47:8}-{Day223/48:15}. Had he done so, we think he would have reached the clear conclusion that it did not.

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¶26.24 John Lewis was shown an email sent by Chris Macey of Wintech, the façade engineering consultants, to Dave White of NHBC on 4 October 2013 in which Mr Macey said that Kingspan K15 was not a material of limited combustibility.^17441744 {NHB00000585}. Mr Macey noted that K15 was widely used and said that Kingspan's marketing material wrongly implied that it was suitable for all applications. He expressed the view, which he said was shared by BRE, that it should not be used without supporting documentation or test data to confirm its acceptability. Mr Lewis rightly accepted that what Mr Macey had said was correct.^17451745 Lewis {Day223/50:20}.

¶26.25 In his email, Chris Macey offered to meet NHBC in order to explain Wintech's concerns, and Dave White began to make arrangements for a meeting.^17461746 {NHB00000585/1}. We return to that meeting below.

¶26.26 Meanwhile, on 31 October 2013, Brian Stevenson, Steve Cook and Paul Williams, three Area Technical Managers employed by NHBC in its Technical Services department, exchanged emails concerning Kingspan K15. Mr Williams said that he had been told that NHBC was no longer accepting K15 on the basis that it was combustible and asked whether NHBC's surveyors had been advised accordingly. Mr Cook said that most surveyors were aware of that view. Mr Stevenson responded that he was certainly not aware that it was NHBC's policy not to accept K15,^17471747 {NHB00000589}. which it had previously accepted on the basis that it held a BBA certificate.^17481748 Stevenson {NHB00003524/2} paragraphs 10-11. Mr Lewis told us that he was surprised by Mr Stevenson's ignorance of that matter.^17491749 Lewis {Day223/53:6-9}.

¶26.27 On 4 November 2013, Paul Williams wrote to NHBC's south-west area technical team saying that John Lewis and Steve Evans were reviewing whether K15 could be accepted for use on high-rise buildings, as NHBC had doubts about its combustibility.^17501750 {NHB00000594/3}. In reality, as we have said above, neither Steve Evans nor John Lewis had any such doubts: they both knew perfectly well that K15 was combustible and thus did not meet the guidance in paragraph 12.7 of Approved Document B for use in the external walls of buildings over 18 metres in height.

¶26.28 Chris Cooley, a Project Surveyor in the Technical Services Department, responded to Mr Stevenson on 8 November 2013 asking how long the promised review would take. He also asked what the alternatives were to using K15 and pointed out that there were no other foam insulation boards that were of limited combustibility and therefore mineral wool was the only material that could be used on high-rise buildings. He stressed that surveyors needed to communicate their requirements at the outset of any design process and warned that a refusal by NHBC to accept K15 would give rise to a major problem with customers who relied on foam board insulation to achieve required U-values.^17511751 {NHB00000594/3}. Mr Cooley warned that Mr Evans should be prepared to receive a barrage of enquiries. That message worked its way up to Steve Evans the same day.^17521752 {NHB00000594/1}. Mr Evans could have been in no doubt, by that point, therefore, about the serious consequences of NHBC's building control officers' having routinely accepted the use of K15 on high-rise buildings in the past and continuing to do so. However, NHBC did not immediately act on what it now knew.

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¶26.29 Although Mr Lewis candidly accepted that a change in NHBC's position on K15 would have resulted in a lot of angry customers, he denied that its failure to act was motivated by commercial considerations.^17531753 Lewis {Day223/60:17-22}. Likewise, Ms Marshall denied that the likely reaction of customers was a factor in its continued acceptance of K15; she said it had not been taken into consideration.^17541754 Marshall {Day225/161:10-19}. In our view, however, in the light of Chris Cooley's email that was not credible.

¶26.30 Ultimately, Mr Evans came to accept that the NHBC's failure to adopt a tougher stance on K15 had indeed been motivated by the likely reaction of its customers. He said that what he characterised as a "knee-jerk" reaction would have caused a lot of disruption to NHBC, which wished to get hold of all the facts before it made a decision.^17551755 Evans {Day219/222:3-20} He claimed that NHBC continued to permit the use of K15 because it had no information that it was not safe,^17561756 Evans {Day219/223:2-17; {Day219/174:11}-{Day219/175:21}. but K15 could not be regarded as safe for use on buildings over 18 metres in height since it was not a material of limited combustibility and its use did not comply with paragraph 12.7 of Approved Document B, as NHBC well knew. Furthermore, NHBC also knew that K15 had been and was still being approved for use in the external walls of high-rise buildings which were not constructed in the same way and with the same components as the system that Kingspan had tested in 2005.^17571757 John Lewis's email of 19 November 2013 {NHB00000604/1}. In those circumstances, NHBC had no reason to think that K15 was generally safe for use on high-rise buildings and every reason to challenge the claim in Kingspan's marketing literature that it was. NHBC's continued endorsement of its use from then on was unjustifiable and amounted to an abdication of its responsibility.

Meeting with Wintech: 15 November 2013

¶26.31 The meeting between Wintech and NHBC took place on the morning of 15 November 2013. John Lewis, Dave White and Graham Perrior represented NHBC; Stuart Taylor and David Watakabi represented Wintech. John Lewis said that meeting had been responsible for bringing concerns about K15 to the forefront of his mind.^17581758 Lewis {NHB00003433} page 12, paragraph 47.

¶26.32 In the hours following that meeting, Mr Lewis compiled a note of the discussions, together with a draft of what he described as an internal guidance note, which he circulated at 14.45 the same day.^17591759 {NHB00000604/4}; {NHB00000605}. The second paragraph of Mr Lewis' note is of particular importance. It described how Wintech had outlined the route to compliance, as recommended in Approved Document B, and set out in bullet points three ways of following it, which formed the basis of his internal guidance note. Although it was described as "internal" at that time, the guidance note eventually became (with only minor amendments) Technical Guidance Note 18, published by the BCA in June 2014.^17601760 Lewis {Day223/74:16-20}.

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¶26.33 One important element in the discussion was Wintech's view, apparently shared by Mr Lewis, that after the 2006 amendments paragraph 12.7 of Approved Document B required all elements of a cladding system to be of limited combustibility, including the external facing material, not only the insulation. The alternative route to compliance was to test the entire proposed system in accordance with BS 8414 and satisfy the performance criteria in BR 135. As a further alternative, a "desktop" opinion from BRE, based on test data, that the performance criteria in BR 135 would be met by the system, would also suffice.

¶26.34 When Mr Lewis was asked why he felt that he needed to recite the guidance in Approved Document B in such detail to his colleagues, he said that, although NHBC already knew it, it had not really digested it.^17611761 Lewis {Day223/63:20-25}. He explained that the guidance in Approved Document B was not second nature to NHBC and that it had not previously understood properly the restrictions on the use of combustible insulation in high-rise buildings.^17621762 Lewis {Day223/64:13-15}. For NHBC as an institution to have had such a poor grasp of the statutory guidance on a matter affecting the safety of life significantly detracted from its ability to discharge its function as an approved inspector.

¶26.35 Although Mr Lewis's notes referred to the use of desktop studies, he candidly admitted that he had never heard of them being provided but said that the representatives of Wintech had told him that other building control bodies had accepted them as demonstrating compliance with the Building Regulations.^17631763 Lewis {Day223/66:15}-{Day223/67:3}. The basis of that part of the guidance was, therefore, purely anecdotal, although in principle a desktop assessment was an acceptable method of demonstrating compliance, provided it was performed competently using appropriate data. However, it was unwise, in our view, to produce draft guidance of that kind, even in its most rudimentary form, without finding out whether BRE, Exova, or other testing houses were capable of producing reliable desktop studies and how widespread was the practice of building control officers' accepting them.

¶26.36 Mr Lewis's notes referred to the Class 0 classification, which it described as "solely a measure of the spread of a flame across the surface".^17641764 {NHB00000604/5}. In fact that was incorrect, because Class 0 refers to both the spread of flame and fire propagation. Mr Lewis said that there was a lot of misunderstanding and confusion within NHBC about Class 0 and that he was not fully aware at the time of the way in which the classification was achieved.^17651765 Lewis {Day223/68:19}-{Day223/69:25}. That confusion about the meaning of Class 0 was not limited to NHBC but was shared by industry generally, and had been for many years.

¶26.37 In the following days, NHBC discussed the guidance note internally. On 19 November 2013 Mr Lewis agreed to put it into a form that would enable it to be presented for consideration at a forthcoming meeting of the BCA.^17661766 {NHB00000604}. He also told Steve Evans in terms that Kingspan had tested K15 only once on a masonry wall construction, that K15 was acceptable only if incorporated into an identical system, and that since most of the schemes being approved by NHBC involved steel-framed constructions it should not be accepting K15, if it intended to follow the guidance in Approved Document B and BR 135.^17671767 {NHB00000604}. Mr Lewis told us that none of his colleagues at NHBC disagreed with that view.^17681768 Lewis {Day223/75:20}.

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¶26.38 Nonetheless, NHBC continued to accept K15 for use on high-rise buildings. In an email sent on 2 December 2013 Steve Evans asked John Lewis for his comments on a draft message he was proposing to send to all NHBC technical staff saying that there was some confusion about whether K15 could be treated as a material of limited combustibility but that until NHBC was in a position to say otherwise, its policy was to continue to accept the use of K15 in rainscreen and masonry construction on buildings over 18 metres in height.^17691769 {NHB00000615/2}. Mr Lewis responded by saying that there was no confusion and that K15 was not a material of limited combustibility. He advised in his email that staff should be told to check with Kingspan first, but that NHBC was obliged in principle to accept the statement in the BBA certificate that K15 could be used in accordance with paragraph 12.7 of Approved Document B (i.e. that it was a material of limited combustibility).^17701770 {NHB00000615/1}. Lewis {Day223/161:14-22}.

¶26.39 Mr Evans' draft and Mr Lewis's response betray serious flaws in NHBC's thinking. First, the language of these communications strongly suggests that Mr Evans was anxious to play down the potential threat to safety by requiring Kingspan to justify the use of K15 in each individual case and in the meantime to continue to accept it for use on buildings over 18 metres in height generally. NHBC knew that K15 could not be used in a system other than one that was identical to the system tested in 2005, which was very different from any of the systems being passed by its building control officers. Secondly, they were both quite wrong to think that NHBC was obliged to endorse the use of K15. On the contrary, as Mr Lewis clearly knew, paragraph 12.7 of Approved Document B did not apply to the product because it was not a material of limited combustibility. Mr Lewis sought to justify his statement by saying that the statement in the BBA certificate that advice should be sought from Kingspan if K15 was proposed for use on high-rise buildings indicated a route to compliance.^17711771 Lewis {Day223/161:14-22}. However, as he ultimately accepted, it did no such thing; the "route" it suggested was, at best, a way of circumventing the guidance in Approved Document B, rather than following it.

¶26.40 At that point, rather than issue a flimsy warning to its staff, NHBC ought to have told them to stop accepting K15 for use in the external wall of any building over 18 metres in height immediately unless and until they had evidence that that system had met the performance criteria in BR 135 following a test under BS 8414. The failure of NHBC to do so reflects a desire at the time to placate customers and manufacturers at the expense of safety.

¶26.41 The BBA certificate was subsequently amended to remove the advice to contact the manufacturer,^17721772 {BBA00000036/6}. but NHBC's policy in late 2013 was conceived before it had any knowledge of that change and cannot therefore be justified by reference to the amended certificate. As Mr Lewis explained, NHBC foresaw that a refusal to accept K15 would have a massive effect across the industry.^17731773 Lewis {Day223/165:16}-{Day223/166:12}. It also believed that any change in its position on K15 would have isolated it from the rest of the industry, as the use of K15 was endorsed by the LABC. As Mr Lewis put it, that led NHBC to ask whether there was any point in rejecting K15 when it was likely to be approved by local authority building control departments.^17741774 Lewis {Day224/19:10-24}. In our opinion, that was an unacceptable approach for NHBC to take.

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Dealings with Kingspan: November 2013 to April 2014

¶26.42 On 26 November 2013, Mr Lewis sent an email to Kingspan asking for advice about the use of K15 on a project involving a building over 18 metres in height.^17751775 {NHB00000644/5}. He noted that K15 was not a material of limited combustibility and therefore asked how the alternative route to compliance in Approved Document B, namely, testing in accordance with BS-8414 and classification in accordance with BR 135, could be achieved. Kingspan's initial response came on 12 December 2013 and merely referred Mr Lewis to the BBA certificate as the basis for the use of K15 on high-rise buildings.^17761776 {NHB00000644/3}.

¶26.43 Mr Lewis was, unsurprisingly, not satisfied with that response and repeated his request the same day.^17771777 {NHB00000644/2}. He explained that his original question had been prompted by the BBA certificate's suggestion that NHBC should seek advice from Kingspan about the suitability of K15 rather than simply reading the product literature. Mr Lewis pointed out that K15 was not a material of limited combustibility and that there had been only one test under BS-8414-1 involving K15 for which results were available. He questioned how K15 could be used as part of a differently constructed external wall or on any system attached to a structural steel frame (which required testing under BS 8414-2).

¶26.44 Mr Lewis had not received any substantive response by the following day and therefore wrote again, with copies to Steve Evans, Dave White and Graham Perrior.^17781778 {NHB00000644}. He said that he and his managers at NHBC wished to raise the matter with Kingspan's management team and requested a meeting in early 2014. He noted that, given the number of affected projects that it was dealing with, NHBC wished to start to advise its customers that K15 did not comply with the Building Regulations or the BBA certificate when used on a building over 18 metres in height.

¶26.45 It is clear from Mr Lewis's email that, despite what its witnesses repeatedly told us, NHBC did not in fact consider that the BBA certificate provided conclusive evidence that K15 was safe or acceptable for use in accordance with the Building Regulations. Indeed, the import of Mr Lewis's message to Kingspan of 13 December 2013 was plainly that the BBA certificate did not support the use of K15 on buildings over 18 metres in height, despite what it said. In our view, NHBC correctly thought that the BBA certificate was wrong in stating that K15 could be used in accordance with paragraph 12.7 of Approved Document B and was free to reject it as proof that K15 was suitable for use under those circumstances. However, it chose not to act on what it knew, pending receipt of an explanation from Kingspan, in order to avoid provoking protests from customers and Kingspan alike. As to that, Mr Lewis had told Mr Evans on 2 December 2013 that he doubted that Kingspan would be able to provide the evidence required to justify the use of K15 on high-rise buildings^17791779 {NHB00000615/2}. but admitted he feared the massive effect across the industry that a change in NHBC's position would cause.^17801780 Lewis {Day223/165:2}-{Day223/166:12}.

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¶26.46 As Mr Lewis conceded, his threat to advise NHBC's customers that K15 was not suitable for use on high-rise buildings was intended to prompt a response from Kingspan.^17811781 Lewis {Day223/125:5-13}. It achieved its aim and Steve Evans, John Lewis, Graham Perrior and Dave White of NHBC met Richard Bromwich, Kingspan's National Business Development Director, and Ivor Meredith, its Technical Project Manager, in January 2014.^17821782 {NHB00000652}. Mr Lewis told us that at the meeting Kingspan had not contradicted his understanding of Approved Document B^17831783 Lewis {Day223/125:23}-{Day223/126:5}. and had confirmed that there was currently only one successful BS 8414 test of a system incorporating K15.^17841784 {NHB00000652/1}.

¶26.47 At that meeting, Kingspan produced a video showing the flame from a blowlamp being applied to a sample of K15 and suggested that, in Mr Lewis' words, "it doesn't burn particularly",^17851785 Lewis {Day223/131:3-10}. notwithstanding the absence of any test data to justify that conclusion. Mr Lewis said he did not think that that was an acceptable, independent or robust way of verifying the suitability of K15,^17861786 Lewis {Day223/131:14}. but NHBC continued to accept the use of the product on high-rise buildings on the basis of an assertion that it was accepted for use on many tall buildings around the world.^17871787 Lewis {Day223/131:3-10}.

¶26.48 John Lewis accepted that he had been aware that Appendices A and B to BR 135 provided that the results of a BS 8414 test could be used to justify the use of a combustible material only in an external wall system that was identical to that which had been tested.^17881788 Lewis {Day223/155:17}-{Day223/157:8}. He also accepted that it had been clear to him that there were simply no test results available to support the use of K15 in the many external wall systems in which it had already been used.^17891789 Lewis {Day223/157:8}. However nobody at NHBC accepted, as they should have done, that the only advice that Kingspan could properly give to its customers was that K15 could not be used at all on buildings over 18 metres in height except as part of a system exactly the same as that tested in 2005.

¶26.49 At that point, NHBC should immediately have stopped approving the use of K15 on buildings above 18 metres in height. However, it did not. It continued to endorse the use of K15, despite the guidance in Approved Document B, because Kingspan was willing to confirm that it was suitable.^17901790 Lewis {Day223/126:21-22}. That approach made no sense, as Mr Lewis accepted in hindsight, but it was adopted because NHBC felt at the time that Kingspan was the only party with detailed knowledge of K15's fire performance.^17911791 Lewis {Day223/127:2-14}. Mr Lewis told us that he had raised concerns with his superiors in NHBC that the justification for approving the use of K15 was becoming ever flimsier but that no change had been made.^17921792 Lewis {Day223/131:15-24}. NHBC's approach of relying uncritically on what Kingspan itself claimed for K15, given that it cannot have been in any doubt that Kingspan was selling K15 on the basis of a self-evidently misleading BBA certificate, demonstrated weakness and a failure to live up to its responsibilities. It was all the more serious for the fact that NHBC was an institution responsible for providing building control services in respect of a large number of new buildings and for ensuring their compliance with the Building Regulations.

174

¶26.50 Although NHBC realised that the BBA certificate was flawed, no one thought to ask the BBA on what basis it had been issued,^17931793 Lewis {Day223/129:6}; {Day223/153:24}-{Day223/155:11}; {Day223/163:5-17}. even though Mr Lewis was not aware of any other BBA certificates which advised the reader to refer to the manufacturer for advice in the same way.^17941794 Lewis {Day223/129:17}.

¶26.51 NHBC held a further meeting with Kingspan on 2 April 2014, attended by John Lewis and Dave White. Mr White reported the results of that meeting to NHBC's technical services managers the same day. He said that for external walls of buildings over 18 metres in height, the only system incorporating K15 for which there was full proof of fire performance was one with a masonry backing wall.^17951795 {NHB00000688/2}. His message was unequivocal. However, even at that point, NHBC did not stop endorsing the use of K15 on high-rise buildings. John Lewis sought to justify that failure by referring to the fact that the BBA certificate for K15 had been revised in January 2014.^17961796 {NHB00000853/11}. That certificate removed the reference to paragraph 12.7 of Approved Document B and the advice to consult the manufacturer, leaving the 2005 test in accordance with BS 8414 as the sole means of achieving compliance.

¶26.52 NHBC discovered the change on or around 25 February 2014.^17971797 {NHB00000689/3-4}. Thereafter, all projects for which an initial notice had been served before January 2014 were accepted on the basis of Kingspan's historic assurances.^17981798 Lewis {Day223/131:3-10}; {Day223/178:20}. NHBC intended those projects for which the initial notice had been served in or after January 2014 to be the subject of a more rigorous assessment of whether K15 could be used.^17991799 Lewis {Day223/134:23}-{Day223/135:5}. It was likely to be several months at least until any new projects reached the stage of completion, during which Kingspan might produce proof that K15 was acceptable for use on buildings over 18 metres in height before NHBC had to take a final position.^18001800 Lewis {Day223/135:20-24}. In our view, that was not a responsible approach for NHBC to adopt. It was well aware that there could be no proof of the kind envisaged because no BS 8414 test results could be applied to high-rise buildings generally, and Kingspan had not produced any desktop assessments from BRE to support such an approach.

¶26.53 On 3 April 2014, Phil Pettinger, a Special Risk Projects Manager employed by NHBC, responded to Mr White's email.^18011801 {NHB00000688/1}. He said that every job involving a building over 18 metres in height that Special Risk Project Managers dealt with proposed or had used K15. He made plain that K15 was being widely accepted by both NHBC and other building control bodies.^18021802 {NHB00000688/1}. John Lewis accepted that it had been clear to him at the time that there was an industry-wide problem with the acceptance of K15 and that Mr Pettinger's email had come as no surprise.^18031803 Lewis {Day223/141:1}-{Day223/142:11}. However, he said that NHBC had not raised the matter with other building control bodies or investigated whether any of them had any other understanding of how K15 could safely be used on buildings over 18 metres in height because of the pressure of time.^18041804 Lewis {Day223/143:1-10}. However, given that NHBC had gained time by waiting for Kingspan to justify the use of K15 on high-rise buildings, we do not understand what the pressure of time was. A simple enquiry of the LABC or the BCA was all that was required.

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¶26.54 On 25 February 2014, Steve Evans asked Mr Lewis to study the new version of the certificate and make an assessment,^18051805 {NHB00000689/3} but it took him until 9 May 2014 to respond.^18061806 {NHB00000689/1}. In the event, his conclusion was that there was no justification for NHBC to continue accepting K15.^18071807 {NHB00000689/1}. Mr Lewis said that NHBC had been hoping that Kingspan would produce a justification for the use of K15 on high-rise buildings but it never materialised. He said that in the meantime, a practice had developed of asking for desktop studies to justify the use of K15 on high-rise buildings,^18081808 Lewis {Day223/176:25}-{Day223/178:14}. but we have not seen any evidence of that.

TGN 18 (Issue 0): draft

¶26.55 The guidance note that Mr Lewis had drafted within hours of NHBC's meeting with Wintech on 15 November 2013 was presented materially unamended as a formal document by Steve Evans to the Technical Working Group of the BCA on 9 December 2013. He proposed that it should be adopted as BCA policy guidance.^18091809 {NHB00000604/2}; {NHB00000605}; Evans {Day219/104:7-9}. It was indeed adopted without material change and became the BCA's Technical Guidance Note 18 (TGN 18), Use of Combustible Cladding Materials on Residential Buildings Issue 0, dated June 2014. It was published in July or August 2014.^18101810 {NHB00000760}.

¶26.56 Like Mr Lewis's guidance note, the proposed guidance put before the BCA in December 2013 referred to three potential routes to compliance with functional requirement B4(1) for the external walls of buildings over 18 metres in height. The first was that all the elements should be materials of limited combustibility, in accordance with paragraph 12.7 of approved Document B. That included the insulation, internal lining board and the external facing material.^18111811 {NHB00000760/2}. That represented Mr Lewis's understanding of the position based on a discussion he had had with Tony Baker of BRE by email in November 2013.^18121812 {NHB00002971}. In that exchange Mr Lewis had said that he thought that the provisions of paragraph 12.7 of Approved Document B extended to external cladding panels because it seemed to him logical to expect them to perform as well as the insulation in a fire.^18131813 {NHB00002971/2}. Mr Baker had responded by saying that all significant elements of the cladding system should be included in any analysis.^18141814 {NHB00002971}.

¶26.57 That approach appears to have reflected BRE's view, at least according to what Dr Sarah Colwell told NHBC in a meeting on 27 November 2014.^18151815 {NHB00000829}. It did not come as a surprise to John Lewis.^18161816 Lewis {Day223/100:12}. However, as the evidence from David Metcalfe of CWCT shows, that was by no means the general view of the industry at the time.^18171817 Metcalfe {CWCT0000115} page 10, paragraph 36. In fact, as Mr Lewis accepted, Approved Document B advised in paragraph 12.7 that insulation materials should be of limited combustibility and in diagram 40 that external surfaces should have a Class 0 or Euroclass B or better classification.^18181818 Lewis {Day223/92:21}-{Day223/94:4}. Accordingly, by suggesting that "all elements" of the external wall should be composed of materials of limited combustibility, TGN 18 presented a restrictive and conservative view of Approved Document B that was not widely shared in the industry.

176

¶26.58 The second option in TGN 18 was for the client to submit evidence that the complete cladding system had been tested in accordance with BS 8414 and classified in accordance with BR 135. TGN 18 did not refer to classifications; instead it stated that the results of a test in accordance with BS 8414 would need to be supported by proof that the acceptance criteria in BR 135 had been met.^18191819 {NHB00000760/2}. Mr Lewis told us that that was simply intended to mean that full test data should be supplied, because NHBC had not realised that BRE would also produce classification reports with any test data.^18201820 Lewis {Day223/105:4}-{Day223/106:12}.

¶26.59 The third option in TGN 18 was the production of a desktop study of the kind that Wintech had told NHBC had been accepted by other building control bodies. However, that was the first time that Mr Lewis had encountered such an approach being adopted in relation to an external wall.^18211821 Lewis {Day223/106:5}-{Day223/108:1}. Wintech had not provided NHBC with any details of how the process would work in practice or any examples.^18221822 Lewis {Day223/204:7-20}. That proposed third route to compliance was entirely theoretical, in as much as it was not based on experience of any such assessments and neither BRE nor any of the other testing houses had been asked whether they could provide desktop assessments and if so how they went about doing so.

¶26.60 Mr Lewis maintained that Appendix A of Approved Document B endorsed the use of desktop studies but he could not recall whether they had been discussed at the meeting with Wintech and there is no evidence to suggest that they had been.^18231823 Lewis {Day223/109:5-11}. He said that he had examined the provisions of Appendix A before drafting the guidance note,^18241824 Lewis {Day223/109:16-21}. but any examination he did carry out can only have been cursory because the guidance note (and accompanying email) had been produced in a matter of hours.

¶26.61 In any event, we do not think that Appendix A of Approved Document B did endorse the use of desktop studies. Paragraph 1 of the introduction, which set the context for what followed, referred to the fact that much of the guidance in the document was given in terms of performance in relation to British or European Standards for products or methods of test or design or in terms of European Technical Approvals. In such cases the guidance required the material product or structure under consideration to have been assessed from test evidence against appropriate standards or by using relevant design guides as meeting the performance required by the tests.^18251825 {CLG00000224/119}. In our view, that provision was clearly referring to the results of tests on the relevant material, product or structure and not to the extrapolation of data from tests on a different material, product or structure.

¶26.62 Moreover, even if it were thought that that passage supported the use of desktop assessments, that reasoning could not sensibly be applied to a complex structure such as the entire external wall of a building. Such an interpretation would undermine the express routes to compliance given in Approved Document B, which required either compliance with the "linear route" or a full-scale test in accordance with BS 8414. It would make no sense for Appendix A to permit the use of combustible materials in circumstances where the proposed structure had not been tested at all.

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¶26.63 That is not to say, however, that a desktop assessment is never acceptable as a means of demonstrating compliance with one of the functional requirements, but it must be based on sufficient accurate test evidence.^18261826 Torero {Day292/92:6}-{Day292/95:16}. NHBC had no basis for promoting desktop assessments as an alternative way of showing compliance with functional requirement B4(1) without identifying the test data that should be used, the method that should be employed or the qualifications that were required on the part of those who were to conduct them.

¶26.64 When Mr Lewis had spoken of the available test data for K15 in his email of 15 November 2013 setting out his draft internal guidance, he had rightly pointed out that any difference between a proposed external wall system and the system that had been tested by Kingspan would prevent any direct reliance on the test result, and that the limited test data available would make it difficult to draw any reliable conclusions about the fire performance of the proposed system.^18271827 {NHB00000604/4}. However, when it came to drafting TGN 18, it appears that NHBC did not consider either of those matters or make any enquiries of BRE about how desktop studies could safely be performed. Mr Lewis told us that NHBC was doing whatever it could to put a guidance note together and simply did not think about consulting BRE.^18281828 Lewis {Day223/111:1}-{Day223/112:19}. Nor did it give any thought to who might be responsible for conducting the desktop studies it was supporting or the qualifications they might need to hold, beyond the rather vague reference to a suitable independent testing body accredited by UKAS.^18291829 Evans {Day220/:47-13}-{Day220/50:19}.

¶26.65 In his witness statement, Mr Lewis said that the third option had been included because he and Mr Evans had wanted to include a route to compliance for those developers who were unable to comply with the two routes described in Approved Document B.^18301830 Lewis {NHB00003433/35} page 35, paragraph 133; Lewis {Day223/189:24-25}. In his oral evidence, however, he said that they were considering all the options and that it had made sense to include it. We do not agree. It was wholly unnecessary and indeed dangerous for NHBC to strive to find a way to help developers who wished to use non-compliant cladding products to do so, having applied little or no thought to that suggested route. The "desktop study" route should not have been suggested by NHBC or the BCA because NHBC had no grounds for thinking that anyone in the industry understood what data was required for a reliable desktop assessment or had the competence necessary to produce one.

¶26.66 In our view, NHBC's desire for a third route to compliance was rooted in three things. First, it had formed a view that the requirements of the "linear route" were particularly onerous. However, that view does not appear to have been shared by the industry at large and, in any event, however onerous, it was not for NHBC to seek to ameliorate the requirements of the guidance.

¶26.67 Secondly, NHBC considered that the tests required by the second option were time-consuming and expensive and were in any event of limited application because they were irrelevant if any element of the system differed from that which had been tested.^18311831 Lewis {Day223/190:8-15}. Again, however, it was not appropriate for NHBC to seek to circumvent or dilute the effectiveness of the guidance by suggesting another route to compliance.

178

¶26.68 Finally, Mr Lewis explained that NHBC did not want to prevent the industry from achieving the high degrees of insulation performance that combustible insulation products provided.^18321832 Lewis {Day223/193:13} However, as a provider of building control services, it was precisely NHBC's role to ensure that unsafe products that were frequently being proposed for use were not approved by its building control officers. Its evident desire to assist the industry was wholly inappropriate. As Mr Lewis was constrained to accept, the practice of building control bodies and approved inspectors "working with" the industry rather than holding it to proper standards was corrupting, because it tended to undermine the independence of building control officers and approved inspectors.^18331833 Lewis {Day223/194:1}-{Day223/196:3}.

¶26.69 Mr Lewis denied that the third route to compliance proposed by TGN 18 had been devised as a means of legitimising schemes using K15 that he knew had been wrongly approved by NHBC in the past.^18341834 Lewis {Day223/196:4-11}. Although we accept his evidence that it arose directly from the suggestion made by Wintech at the meeting on 15 November 2013, that was all it was, a suggestion based on hearsay and anecdote. The evidence shows that NHBC clearly understood that the use of K15 could not be justified by any other means and that refusing to approve the use of K15 on high-rise buildings would have significant commercial repercussions.

TGN 18 (Issue 0): June 2014

¶26.70 TGN 18 was formally issued in June 2014.^18351835 {NHB00000760}. The three alternative routes to compliance were identical to those included in John Lewis's initial draft prepared on 15 November 2013, save that a sentence had been added to the second route to identify some of the requirements of BR 135. There is no evidence that the BCA itself took any steps to verify or investigate the validity and safety of the three options, in particular to examine the basis for option 3, and we infer that it did not.

¶26.71 In the result, the BCA promulgated the third route to compliance on the basis of extremely limited information, namely the second-hand assurances of Wintech, and without any independent verification or indication of how it could operate in practice. Moreover, although each of the NHBC witnesses sought to justify its inclusion by reference to Appendix A of Approved Document B, there is no evidence that it had received any consideration within NHBC or the BCA.

¶26.72 In the circumstances, the inclusion of the third option in TGN 18 was irresponsible. It was not motivated by a desire for rigour in the application of Approved Document B, nor by a desire to improve fire safety standards in high-rise buildings, but by NHBC's desire to assist developers to find a way to justify the use of non-compliant products.

Discussions with the government and industry: 2014 – 2015

¶26.73 On 2 July 2014 Brian Martin of the department sent an unprompted email to Neil Smith of NHBC to provide a "friendly warning" that PIR insulation was being used in cladding systems. He did so because, as he put it, people were under the impression that PIR was a material of limited combustibility (which was not the case) and he thought that NHBC ought to ensure that its surveyors were aware of that.^18361836 {NHB00000732/3}. Mr Martin's email was sent at 11.42, shortly before a meeting of the CWCT at 14.00 that day. Mr Martin attended that meeting but did not stay until the end.^18371837 Lewis {Day224/5:4-22}.

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¶26.74 Mr Martin's email came as no surprise to NHBC, as it had been endorsing the use of PIR insulation since at least November 2013 in the full knowledge that it was not a material of limited combustibility.^18381838 Evans {Day220/67:3}-{Day220:68:5}. It took NHBC until 11 July 2014 to respond and when the response came, it came from Steve Evans, to whom Mr Smith had passed Mr Martin's email. Mr Evans drafted a response and discussed it with Diane Marshall before it was amended and sent.^18391839 {NHB00000732/1}. He said that there was no reason to suspect that buildings which had been built with Kingspan K15 were at risk; it was just the fact that testing carried out to date did not bear that out. Kingspan, he said, was confident that the testing currently being carried out would prove the suitability of the material for use on buildings over 18 metres in height.^18401840 {NHB00000732/2}

¶26.75 The first sentence was clearly misconceived.^18411841 Evans {Day220/90:2-25} Although Mr Evans did not accept it,^18421842 Evans {Day220/91:1}-{Day220/93:11} the fact that there was no available test evidence to indicate that K15 was compliant was itself a reason to suspect that buildings on which it had been installed were at risk. The statement amounted to a suggestion that any untested combustible insulation material was safe for use on buildings over 18 metres in height unless testing proved otherwise. That was obviously not the case. For her part, Ms Marshall sought to explain that sentence by saying that the high-rise buildings containing K15 which NHBC had approved in the past had been accepted on the basis of the BBA certificate.^18431843 Marshall {Day226/16:1}-{Day226/18:4}. However, the sentence does not say that NHBC had relied on the BBA certificate and, for reasons already given, the BBA certificate for K15 was plainly unreliable. She also told us that she had placed confidence in the fact that Kingspan had told NHBC that it was going to conduct more tests,^18441844 Marshall {Day226/17:25}-{Day226/18:4}. but that was not a sound basis for the assertion that tall buildings with K15 in their external walls were not at risk.

¶26.76 The second sentence of Mr Evans' email merely perpetuated the falsehood, disseminated by Kingspan with the assistance of NHBC and with the inadvertent support of the LABC and the BBA, that a single successful BS 8414 test could support the generic use of K15 in external walls of buildings over 18 metres in height generally, irrespective of the construction of the system. It could only have made sense if Steve Evans had been suggesting that Kingspan would subject every external wall system in which K15 had been used (of which there were very many) to a BS 8414 test, but that was clearly not his intention. As John Lewis accepted, that would require a vast number of tests (as many as there were different external wall systems containing K15), occupying BRE for months.^18451845 Lewis {Day224/14:6-22}.

¶26.77 The correspondence was not sent to John Lewis until 15 August 2014 and he was not consulted on its contents.^18461846 Lewis {Day224/4:15}-{Day224/5:25}; {Day224/11:11-16} Mr Lewis said that NHBC did not see Mr Martin's email as a reason to change anything it was doing because it was already aware of the historic legacy of buildings containing combustible insulation, was continuing to press Kingspan for the results of tests on K15 (thus far without success), and in any event had already drafted TGN 18 as a response to the problem.^18471847 Lewis {Day224/9:18-25}.

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¶26.78 Steve Evans' response to Brian Martin contrasted starkly with the position he had taken in correspondence with Kingspan the previous month. On 16 June 2014, he had told Richard Bromwich of Kingspan that the change in the BBA certificate for K15 meant that NHBC had no remaining basis for accepting its use on buildings over 18 metres in height.^18481848 {NHB00000757/3}. He warned that unless Kingspan could produce additional test evidence supporting the use of K15 in constructions which differed from the BS 8414-1 test referred to in the BBA certificate by 30 June 2014, NHBC would need to reconsider its acceptance of K15 on such buildings. That was some six months after its meeting with Kingspan in January 2014. NHBC must have realised by that point, if not earlier, that it was being deceived by Kingspan. Mr Evans' message of 16 June 2014 simply gave Kingspan a further opportunity to keep selling K15 for use on buildings over 18 metres in height in the UK market safe in the knowledge that NHBC had not instructed its surveyors to reject it.

¶26.79 In the event, Mr Evans' deadline of 30 June 2014 came and went without any action being taken by NHBC. Instead, it continued to give Kingspan further time to produce the results of tests that it must have known could not provide a satisfactory resolution. Mr Lewis said that had been because a change in NHBC's position would have created a storm within the industry and would in any event have been futile because local authority building control officers would have accepted the use of K15 based on the LABC certificate, which stated that it could be considered a material of limited combustibility.^18491849 Lewis {Day224/18:3} – {Day224/19:24}. That was not a responsible position for NHBC to take.

¶26.80 By August 2014, NHBC was clearly becoming increasingly uncomfortable with Kingspan's failure to provide convincing evidence that K15 was suitable for use on high-rise buildings. On 15 August 2014, Steve Evans wrote to Ivor Meredith of Kingspan requesting a letter of comfort from BRE pending receipt of further promised test results in order to protect everyone's position in circumstances where it could be months before the further information was received and there were many designers currently using or planning to use K15.^18501850 {NHB00000757/1}.

¶26.81 That was itself a telling request for a number of reasons. First, it is wholly unclear what comfort Kingspan could give in relation to the use of K15 on buildings over 18 metres in height. Secondly, it revealed that NHBC knew that it was open to criticism and possibly claims for accepting K15 for use on high-rise buildings when it knew that it did not comply with the guidance in Approved Document B and could therefore not demonstrate compliance with the Building Regulations by the linear route. Thirdly, it treated Kingspan and NHBC as if they had a common interest in Kingspan's continuing to market K15 for use on high-rise buildings. That was a fundamental misconception. It was NHBC's responsibility as an approved inspector to ensure that its surveyors and building control officers applied the Building Regulations correctly and rejected the use of any materials or products that would prevent the building from complying with them. The action of NHBC provides a vivid example of a large body with substantial influence over building control officers nationwide electing to co-operate with manufacturers rather than robustly enforce regulations designed to protect life. The attitude of NHBC, as revealed by Mr Evans' message, deserves criticism in the strongest terms.

181

Meeting with Arup and BRE: autumn 2014

¶26.82 On 30 October 2014, Steve Evans wrote to Dr Barbara Lane of Arup Fire seeking a meeting to discuss technical issues relating to the use of combustible materials in the external facades of high-rise buildings.^18511851 {NHB00000811/4}. In her response Dr Lane said that Arup believed that the use of combustible materials in residential buildings was an accident waiting to happen.^18521852 {NHB00000811/3}. A meeting then took place between Arup and NHBC on 25 November 2014.^18531853 {NHB00000829/1}. Despite Arup's clear concerns, NHBC did not think to tell Brian Martin that, contrary to the previous assurances given by Steve Evans in his letter of 11 July 2014, there was indeed a real risk to existing buildings.^18541854 Evans {Day220/154:15}-{Day220/158:3}. Nor did NHBC, even at that late stage, a year after the Wintech meeting, start refusing to accept K15 for use on high-rise buildings.^18551855 Evans {Day220/157:1-11}.

¶26.83 On 27 November 2014, Steve Evans, John Lewis, Graham Perrior and Dave White of NHBC met Dr Sarah Colwell, Steve Manchester and Stephen Howard of BRE. At that meeting, NHBC was told that the time between a BS 8414 test and the consequent BR 135 classification was usually short and learned that no classification report had been issued in relation to K15.^18561856 {NHB00000829/2}. Therefore, despite BRE's unwillingness for reasons of client confidentiality to answer specific questions about Kingspan's latest tests, it was clear to NHBC that at least one of them had failed.^18571857 Lewis {Day224/89:20}-{Day224/90:14}.

¶26.84 Dr Sarah Colwell also confirmed that BRE had agreed with NHBC's view that the provisions in paragraph 12.7 of Approved Document B applied to all major components of a cladding system, including the external finish.^18581858 {NHB00000829/2}. John Lewis specifically asked Sarah Colwell about that because of the resistance to that view that NHBC was receiving from customers. He wanted BRE to confirm that in its view Option 1 in TGN 18 issue 0 interpreted that paragraph correctly.^18591859 Lewis {Day224/69:8-12}. However, Dr Colwell did not explain how she derived that meaning from the language of paragraph 12.7.^18601860 Lewis {Day224/69:1-7}.

Contact with the BBA: January 2015

¶26.85 NHBC did not contact the BBA about its certification of Kingspan K15 until January 2015, some seven years after the BBA certificate had first been published and a year after the certificate had been amended to remove the instruction to seek advice from Kingspan.^18611861 {NHB00000895/3}. On 27 January 2015, Graham Perrior asked John Albon of the BBA to explain why the certificate had been changed, which he said had seriously affected the situations in which K15 was acceptable.^18621862 {NHB00000895/3}.

182

¶26.86 The BBA provided a comprehensive response the following day, the essence of which was that the change to the certificate was a matter of emphasis and there had been no change in the assessment criteria or scope of approval.^18631863 {NHB00000898/2}. When he saw that response, Graham Perrior was unimpressed. He passed it on to Dave White and Steve Evans that day saying that the BBA's position was not correct.^18641864 {NHB00000899}. Regrettably, no one at NHBC had asked the BBA to explain its statement that K15 could be used in accordance with paragraph 12.7 of Approved Document B and Mr Evans could not explain why it had not done so.^18651865 Evans {Day221/52:15-18}. Mr Evans maintained before us that even at that stage NHBC could continue to rely on the BBA certificate to approve the use of K15 on high-rise buildings because it said that it could be used in accordance with paragraph 12.7 of Approved Document B, but we find it difficult to understand that position, given that K15 was known not to be a material of limited combustibility.^18661866 Evans {Day221/53:18-24}.

Reliance on TGN 18

¶26.87 On 5 February 2015 NHBC told Kingspan that it would no longer approve the use of K15 on high-rise buildings unless evidence of compliance with the Building Regulations was provided in accordance with TGN 18.^18671867 {NHB00000922/1}. Kingspan's response was to instruct its lawyers to allege that it was being treated unfairly and to threaten legal action against NHBC.^18681868 {KIN00008283}.

¶26.88 NHBC's new policy applied to all projects using K15 from 1 January 2014.^18691869 {NHB00000934}. However, NHBC continued to accept confirmation from Kingspan that K15 was suitable for any project for which the initial notice had been given before that date.^18701870 As per Steve Evans's instructions on 2 December 2013 at {NHB00000935} as set out in {NHB00000934}. John Lewis accepted that K15 was no less combustible on 31 December 2013 than it had been on 1 January 2014, and could not explain why NHBC had not changed its approach.^18711871 Lewis {Day223/157:25}-{Day223/158:17}. In our view, the policy adopted by NHBC in early 2015 towards the continued acceptance of Kingspan K15, despite what it knew, could not reasonably be justified.

The 2015 policy review

¶26.89 Following the adoption of its new policy towards K15, NHBC launched what it termed the "Combustible Cladding Review".^18721872 Lewis {NHB00003433/32} page 32, paragraph 115. In accordance with the instructions of the board,^18731873 Marshall {Day226/32:7-15}. the review was limited to buildings over 18 metres in height currently under construction or about to start.^18741874 Lewis {Day224/158:22}-{Day224/159:5}; Marshall {Day226/5:14-19}. The board also decided not to tell its previous customers that NHBC had approved external cladding systems on high-rise buildings that contained combustible insulation.^18751875 Marshall {Day226/33:25}-{Day226/34:7}. That decision was apparently based, at least in part, on the fact that at the time NHBC had held what it regarded as a valid BBA certificate.^18761876 Marshall {Day226/33:15}-{Day226/34:19}. We have no reason to doubt that that was in fact in part the basis of its decision. However, we do not accept Ms Marshall's assertion that the BBA certificate for K15 ever justified such an approach, certainly not after NHBC had become aware that it was erroneous and unreliable. The board's decision not to tell previous customers of the fact that its building control officers had approved cladding systems that were at least at serious risk of preventing the building from complying with one of the principal functional requirements of the Building Regulations, and so a potential danger to life, was irresponsible.^18771877 Marshall {Day226/33:25}-{Day226/34:19}. As we shall see, the scale of the problem was huge.

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¶26.90 The review categorised buildings as being either high, medium or low risk according to the materials used in their construction.^18781878 Lewis {NHB00003433/32} page 32, paragraph 118. Those categories had been suggested by John Lewis based on his knowledge of combustible materials and were accepted by Steve Evans.^18791879 Lewis {Day224/164:13-19}. Mr Lewis described the review as a screening exercise, although he conceded that some projects with ACM PE had slipped through the net.^18801880 Lewis {Day224/164:20}-{Day224/165:14}.

¶26.91 The results of the review were subsequently put into a table that identified in detail the projects in which NHBC had been involved that included the use of combustible materials.^18811881 {NHB00003038}. All the buildings in the review were ultimately accepted by NHBC, despite containing combustible materials,^18821882 Evans {Day221/19:3-18}. although many required remedial work to be carried out before they could be finally approved.^18831883 Lewis {Day224/168:7-10}. NHBC's approval was ultimately given by Steve Evans and Diane Marshall, neither of whom had any fire engineering qualifications, based on the advice and expertise of John Lewis or Maulik Katkoria as fire engineers.^18841884 Evans {Day221/41:18}-{Day221/43:21}.

Revision of TGN 18: June 2015

TGN 18 (Issue 1): June 2015

¶26.92 Issue 1 of TGN 18 was published by the BCA in June 2015. That revision had been drafted by John Lewis at the request of Steve Evans^18851885 Lewis {Day224/91:1}-{Day224/92:4}; {Day224/99:21-23}. and contained two major changes. First, the pool of people who could produce desktop studies was widened to include any suitably qualified fire specialist. Secondly, a holistic fire engineering solution was included as a fourth alternative route to compliance.

¶26.93 John Lewis^18861886 Lewis {NHB00003433/38} page 38, paragraph 148; Lewis {Day224/99:13}-{Day224/100:19}. and Steve Evans^18871887 Evans {NHB00003020/77} page 77, paragraph 200 (a). said that the first change had been prompted by responses from the three testing houses which said that they were struggling to keep up with the number of requests for desktop studies. However, we have not seen any contemporaneous documents to suggest that that was the case and it was certainly not mentioned in the minutes of the meeting between BRE and NHBC in November 2014.^18881888 {NHB00000829/2-3}. We think that if BRE had been inundated with requests for desktop reviews, Dr Colwell would probably have raised the matter at the meeting with NHBC on 25 November 2014, but there is no evidence that she did. Although Mr Evans recalled a discussion about it, Mr Lewis did not.^18891889 Lewis {Day224/111:16}-{Day224/112:18}. We prefer Mr Lewis' recollection, given the total absence of any reference to the matter in the contemporaneous documents. In our view, it is more likely that the change was motivated by a desire on the part of NHBC to make it easier for developers to obtain timely building control approval.

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¶26.94 The second change was the inclusion of a holistic fire-engineered solution. That had always been an alternative way of demonstrating compliance with functional requirement B4(1), as clearly provided by Approved Document B.^18901890 {CLG00000224/15}, at paragraph 0.30. It was included simply for completeness.^18911891 Lewis {Day224/95:6-23}.

Option 3 and desktop studies

¶26.95 As NHBC's only qualified fire engineer, John Lewis was responsible for examining the desktop studies that it received.^18921892 Lewis {Day224/115:21-25}. He found them to be of variable quality, those from BRE and Exova being the most comprehensive.^18931893 Lewis Second Statement {NHB00003433/48} page 48, paragraph 182 (b). Initially he found few problems with the studies he received, but after the publication of Issue 1 of Technical Guidance Note 18 in June 2015 the standard began to drop.^18941894 Lewis {Day224/123:23}-{Day224/124:19}. He did not accept, however, that those who were permitted to produce reports were not qualified to do so.^18951895 Lewis {Day224/124:20}-{Day224/125:7}.

¶26.96 John Lewis reported his concerns to Diane Marshall,^18961896 Marshall {Day226/59:2-10}. who was aware that some desktop studies submitted to NHBC often lacked proper references to relevant test data and that others applied only the requirements of diagram 40 of Approved Document B as opposed to the guidance in paragraph 12.7.^18971897 Marshall {Day226/60:11-22}. She nonetheless claimed to believe that desktop studies worked well so long as they were done correctly.^18981898 Marshall {Day226/61:6-13}. However, there was no established method for assessing whether they had been done correctly.

¶26.97 In his report Professor Luke Bisby expressed the view that the change to TGN 18 in relation to desktop studies further eroded the already weak oversight of competence in this part of the industry.^18991899 Bisby, Phase 2 Report - BR 135 Desktop Assessment Report {LBYP20000004/37} paragraph 277. We agree. It is clear that in 2015 the practice of producing desktop assessments was fraught with dangerous shortcomings.

Further discussions with industry: 2015–2016

Paragraph 12.7 of Approved Document B and "filler"

¶26.98 On 15 June 2015, Steve Evans wrote to Brian Martin, whom he regarded as the "guardian of Approved Document B",^19001900 Evans {Day221/68:15-17}; {NHB00002792/3}. to seek clarification of the meaning of "filler material etc" in paragraph 12.7 of Approved Document B.^19011901 {NHB00002792}. He was keen to know what the department understood "filler" to mean and whether the suggested restriction to materials of limited combustibility extended to the external surface of a cladding panel. Given that NHBC had taken the view when drafting TGN 18 that all elements of the external wall construction should be materials of limited combustibility (a view shared by BRE), it is surprising that Mr Evans felt that he had to ask those questions. However, he told us that many of NHBC's customers had been challenging its view that paragraph 12.7 required cladding panels to be composed of materials of limited combustibility rather than simply being classified Class 0.^19021902 Evans {Day221/55:16}-{Day221/56:15}. The key point was that contained in the last paragraph of the email. NHBC was of the view that there was little point in ensuring that insulation products were materials of limited combustibility if they could be faced with a cladding finish which, although Class 0, could contribute to the spread of fire, but there was a difference of opinion within the industry. For that reason, he was seeking clarification from the department.

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¶26.99 Despite NHBC's plea for help, Mr Martin's response was that he could not offer a formal view, because the interpretation of Approved Document B as it applied to specific projects was a matter for the relevant building control body.^19031903 {NHB00002792/4}. As Mr Evans said at the time, that was not an answer at all.^19041904 {NHB00002792/2}. Nonetheless, Mr Evans did not press Mr Martin for a clearer statement and Mr Lewis thought that his existing response might be enough to justify the position taken by NHBC in its discussions with one particular developer.^19051905 {NHB00002792}; Evans {Day221/72:4-23}. Although NHBC had confidence in its own view that all components of the external wall of a high-rise building should be materials of limited combustibility, large swathes of the industry disagreed. Given NHBC's powerful influence in the industry, it is regrettable that it did not press Mr Martin to adopt a clear position.

BRE and Siderise Conference: January 2016

¶26.100 On 13 January 2016, Steve Evans attended a conference on external facades organised by BRE and Siderise. He gave a presentation entitled Facades to Tall Buildings: Routes to Compliance and took questions from the audience. Among those present was Nick Jenkins of Booth Muirie, a supplier of rainscreen materials, including aluminium composite panels.^19061906 Murden {BLM00000004/1} page 1, paragraph 7. During the question and answer session, Mr Jenkins explained that combustible ACM panels were commonly being used on high-rise residential buildings and expressed his grave concern that they did not meet the requirements of the Building Regulations.^19071907 {INQ00014949/10-11}. Mr Evans' response was that an ACM panel with a Class 0 classification was considered to comply with Approved Document B.^19081908 {INQ00014949/12}. He referred to what he described as an anomaly in Approved Document B created by the different requirements of paragraph 12.7 and Diagram 40. Although he acknowledged that ACM panels could technically be compliant if they met the requirements of Diagram 40, he said that that was not an approach he agreed with.^19091909 {INQ00014949/12 -13}. The video clip is at {SIL00010066}, played at {Day 221/79:4-15}.

¶26.101 Mr Evans's own position was that NHBC could not demand higher standards than those required by the Building Regulations.^19101910 Evans {Day220/167:7}-{Day220/170:24} and {Day221/37:6-23}; Lewis {Day224/188:13}-{Day224/189:8}. That may be so, but it begs the question what the Building Regulations actually required. Mr Evans confirmed that NHBC's position as expressed in Option 1 of TGN 18 (both Issues 0 and 1), namely, that all elements of the external wall of a high-rise building had to be of limited combustibility, had not altered between June 2014 and January 2016.^19111911 Evans {Day221/89:5-7}. There was therefore an obvious inconsistency between what he told the conference and NHBC's approach at the time, which he sought to explain away by saying that his answer at the conference had been badly worded.^19121912 Evans {Day221/87:14}-{Day221/88:6}. He said that his claim to have discussed with the department what he called the anomaly in Approved Document B was a reference to NHBC's email exchange with Brian Martin in June 2015, although, as NHBC recognised at the time, those perfunctory discussions had not advanced matters at all.^19131913 Evans {Day221/90:1}-{Day221/91:9}.

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¶26.102 The significance of the conference in January 2016 was twofold. First, Mr Evans did not adopt the position set out in TGN 18, and thus publicly adopt a clear position, even though it might, on one reading of Approved Document B, be over-strict. Secondly, the discussion brought home to NHBC (if it had not realised it earlier) that there was a significant number of high-rise buildings in the UK which its building control surveyors (and others) had approved as compliant with the Building Regulations but which contained combustible materials in the external wall systems that should not have been accepted.

¶26.103 On 19 January 2016, after the conference, Mr Jenkins took the matter up with Steve Evans in email correspondence, picking up the ambiguities in some of the responses given by the panel at the conference. He asked whether the entire external wall of a high-rise building had to be of limited combustibility or whether, where ACM cladding panels were used, it was sufficient that they be classified Class 0.^19141914 {BLM00000211/4}. Steve Evans responded on 29 January 2016 saying that Approved Document B advised that all materials used in the external wall should comply with both paragraph 12.7 and Diagram 40, thereby contradicting the view he had expressed at the conference.^19151915 {BLM00000211/2}. Mr Evans fairly acknowledged before us that his position was indeed directly inconsistent with what he had said at the conference but insisted that it was what he had been trying to express.^19161916 Evans {Day221/100:22-23}. We are not convinced by that answer, not least because Mr Evans took ten days to respond to Mr Jenkins, during which time he had had plenty of time to think about the point carefully.

¶26.104 Although Steve Evans told us that NHBC would not have approved any buildings clad in ACM panels with unmodified polyethylene cores,^19171917 Evans {Day221/120:4}-{Day221/121:7}. we do not accept that. John Lewis conceded that the 2015 review had revealed a number of such buildings that had been approved by NHBC.^19181918 Lewis {Day225/42:17}-{Day225/45:25}. By early 2016 at the latest NHBC knew at the highest levels of its management that there were a substantial number of high-rise buildings in the UK on which ACM panels with unmodified polyethylene cores had been installed and which had been passed as compliant by NHBC's building control surveyors.^19191919 Lewis {Day225/42:17}-{Day225/45:25}.

The July 2016 guidance note

¶26.105 After NHBC changed its policy in February 2015 to require proof of compliance with the Building Regulations in accordance with TGN 18, it noticed that it was frequently being provided with the same desktop study amended in insubstantial ways to cater for differences between projects.^19201920 Lewis {NHB00003433/53} page 53, paragraph 194. As no further test data had been forthcoming from Kingspan, despite a string of promises stretching back to January 2014, NHBC realised that it was likely to continue to receive desktop studies based on the same data. It therefore decided that it could dispense with the requirement for such studies altogether for certain façade systems.^19211921 Lewis {NHB00003433/54} page 54, paragraph 195.

¶26.106 Accordingly, in July 2016, NHBC published a guidance note entitled Acceptability of Common Wall Construction Containing Combustible Materials in High Rise Buildings.^19221922 {NHB00001293}. The note was drafted by John Lewis and approved by Steve Evans, Diane Marshall, Ian Davis and the NHBC Executive Committee.^19231923 Lewis {NHB00003433/55-56} pages 55-56, paragraphs 204-205. The new guidance set out functional requirement B4(1) and the four options contained in Issue 1 of TGN 18, which it described as alternative ways of demonstrating compliance with the Building Regulations. It went on to say that the new guidance had been produced to provide advice to builders on some of the most common wall types in relation to which NHBC would no longer require a desktop assessment in accordance with Option 3 in TGN 18 in order to demonstrate compliance.

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¶In the appendices it described three common wall and façade types that were acceptable to NHBC without the need to provide a desktop assessment provided that the design specification and installation met the minimum requirements set out in the appendices.

¶26.107 Appendix 3 covered aluminium composite panels. The requirements for automatic approval included the use of panels with a minimum Euroclass B classification and a Class 0 classification for surface spread of flame. Also acceptable as part of the system were Kingspan K15 and Celotex RS5000 insulation boards.

¶26.108 Diane Marshall told us that NHBC had been prompted to issue the guidance partly by the poor quality of the desktop studies submitted to it and partly by the administrative burden of reviewing many assessments relating to similar systems,^19241924 Marshall {Day226/62:14-18}. but clearly neither of those was a good reason for NHBC to abdicate its responsibility for examining carefully the proposed structure of an external wall. Ms Marshall sought to justify NHBC's approach by reference to regulation 7 of the Building Regulations and said that it was common knowledge that past experience could be used to inform future decisions.^19251925 Marshall {Day226/73:9-21}. However, no one at NHBC had ever examined Approved Document B to see whether that was a permissible approach.^19261926 Marshall {Day226/74:18-23}. We do not think it was.

¶26.109 Paragraph 1.18 of the Approved Document supporting regulation 7 states that past experience, such as the use of a material in an existing building, may show that it can perform the function for which it is intended.^19271927 {INQ00014930/14}. Ms Marshall conceded that a cladding system would need to comply with functional requirement B4(1) in order to demonstrate that the same system, if installed on another building, could perform the function for which it was intended as contemplated by regulation 7. However, she appeared not to grasp the important point that a previous desktop assessment could never demonstrate compliance in the absence of relevant test data relating to the particular system being used as the exemplar.^19281928 Marshall {Day225/73:9}-{Day225/74:10}.

¶26.110 Both Diane Marshall and Steve Evans agreed that the guidance note published by NHBC involved drawing an inference from underlying assessments that were themselves based on inferences from some underlying data.^19291929 Marshall {Day226/70:14-23}. However, NHBC was not concerned by the fact that there had been no large-scale testing of any systems incorporating ACM panels,^19301930 Evans {Day221/138:11}-{Day221/139:25}. and the guidance note was published without any contribution from organisations such as BRE or Exova.^19311931 Evans {Day221/147:24}-{Day221/148:7}. That was particularly surprising given that NHBC was aware of the international cladding fires involving ACM panels in 2015 and early 2016.^19321932 Evans {Day220/19:14-17}; {Day220/21:20-23}; Lewis {Day225/8:18-22}.

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¶26.111 Appendix 3 did contain a warning that the use of aluminium composite panels with polythene or polythene and mineral cores which did not achieve a Euroclass B classification fell outside the scope of the guidance.^19331933 {NHB00000065/4}. Diane Marshall said that that had been intended to mean that all panels with polyethylene cores were prohibited in addition to those with fire retardant cores that had not achieved Class B.^19341934 Marshall {Day226/79:4-16}. In other words, she suggested that the clause "which do not achieve a minimum Class B combustibility classification" was to be read as if in parenthesis, so that all ACM panels with unmodified or modified polyethylene cores fell outside the guidance.^19351935 Marshall {Day226/83:1-24}. We are unable to accept that interpretation. First, no one at NHBC suggested that the passage was intended to have that meaning until Ms Marshall proposed it in the course of her evidence. Secondly, and more importantly, some ACM panels with fire retardant polyethylene cores can be classified Class 0 and Euroclass B. Indeed, some of Arconic's Reynobond FR core panels were. No-one at NHBC had done any research before the note was published on the fire-retardant versions of ACM panels and their corresponding Euroclass classifications, and there was therefore no basis on which to ban all panels with polyethylene cores regardless of their mineral content.^19361936 Lewis {Day225/35:22}-{Day225/37:4}. Thirdly, if that had been intended, it would have been easy simply to say that all ACM panels with polyethylene cores fell outside the scope of the guidance note, without referring to any classification.

¶26.112 We think it clear that the sentence meant what it says, namely, that only ACM panels with polyethylene cores that were classified Class 0 or Euroclass B were covered by the guidance, without regard to the nature of the core. Mr Lewis, who drafted the note, told us that he thought that it would effectively exclude ACM panels with unmodified polyethylene cores, but he could not explain why he had not said so plainly.^19371937 Lewis {Day225/33:24}-{Day225/35:21}.

¶26.113 The guidance note was silent on the size and orientation of the cladding panels, the spacing between them, the fixing method (cassette or riveted) and the width of the drained and vented cavity, all of which were capable of affecting the fire performance of the system as a whole. Steve Evans said that the guidance note was intended to apply to external wall systems that were practically identical to those in the numerous desktop studies submitted to NHBC,^19381938 Evans {NHB00003020/102} page 102, paragraph 251 a. but he was unable to explain what that meant.^19391939 Evans {Day221/147:12-22}.

¶26.114 Diane Marshall conceded that the guidance note permitted the use of external wall systems containing insulation and cladding that were not materials of limited combustibility and was therefore inconsistent with her understanding of paragraph 12.7 of Approved Document B.^19401940 Marshall {Day226/90:22}-{Day226/91:7}. At least if, as she thought, all elements of the cladding system had to be material of limited combustibility, as Option 1 in TGN 18 provided. Although the witnesses denied it,^19411941 Lewis {Day225/51:18}-{Day225/52:5}. the 2016 guidance note was clearly inconsistent with the policy NHBC had adopted in 2015 and, as Kingspan said in an internal email of 8 July 2016, eased the passage of compliance for K15.^19421942 {KIN00002297/1}. Given the trouble that NHBC had had with Kingspan since early 2014, the sudden blanket approval of the use of K15 in the external walls of buildings over 18 metres in height was, to say the least, surprising.

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¶26.115 The guidance note was presented to an NHBC conference in London on 7 July 2016. It is a tragic irony that that was the same date as the issue by RBKC's building control officer of the certificate of practical completion for the Grenfell Tower refurbishment, the new cladding on which was composed of Celotex RS5000, a small amount of Kingspan K15 and ACM panels with unmodified polyethylene cores that purported to hold a Euroclass B classification.

¶26.116 For NHBC building control officers the guidance note was effectively a substitute for Approved Document B. For them to accept an external wall as complying with functional requirement B4(1), it was no longer necessary for the insulation (let alone all the elements) to be of limited combustibility, or, as an alternative, to have a full system test meeting the criteria in BR 135, or a desktop assessment, or a holistic fire-engineered solution. It was sufficient for the external wall to be composed of the common products listed. It drove a coach and horses through the guidance in Approved Document B and rendered TGN 18 completely irrelevant. There is no evidence that the BCA was ever consulted about it. We agree with Mr Lewis when he said that the guidance note should never have been produced.^19431943 Lewis {Day225/60:1-9}.

Events after the fire at Grenfell Tower

Approach from Brian Martin

¶26.117 On 16 June 2017, two days after the fire at Grenfell Tower, Brian Martin wrote to Diane Marshall attaching a script written to rebut a newspaper article which had stated that ACM panels with polyethylene cores complied with the guidance in Approved Document B.^19441944 {NHB00001460/2}; {NHB00001458}. He asked whether she would be prepared to make a public statement to that effect as an independent expert. Ms Marshall told us that she did not know why Brian Martin had approached her and had not given any thought at the time to whether it was appropriate for him to do so.^19451945 Marshall {Day226/103:1}-{Day226/104:9}.

¶26.118 In contrast to the guidance note published by NHBC in July 2016, the script stated that only materials of limited combustibility could be used in the external walls of buildings over 18 metres in height.^19461946 Marshall {NHB00003434/43} page 43, paragraph 201. Nonetheless, Diane Marshall told Brian Martin that she fully agreed with the proposed text.^19471947 {NHB00001460/1}. She did not, however, agree to act as the required independent expert and instead suggested he approach the chairman of the BCA.^19481948 {NHB00001460/1}. She said that her decision had not been motivated by the obvious inconsistency between the position of NHBC and that of the department but by the fact that she did not consider NHBC's views to be representative of the industry.^19491949 Marshall {Day226/105:16}-{Day226/109:18}. We find that an unconvincing explanation given the influence of NHBC nationally, its role in the production of TGN 18 and the issue of its guidance note.

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Withdrawal of the guidance note

¶26.119 On 26 June 2017, Brian Martin wrote to Diane Marshall again to say that NHBC's 2016 guidance note had been raised in response to the Grenfell Tower tragedy, but he offered no further explanation. He questioned its evidential basis and asked for the test results from any BS 8414 testing which had taken place using Class B ACM panels.^19501950 {NHB00001465/2}.

¶26.120 On 28 June 2017, NHBC withdrew the 2016 guidance note on the basis of commercial considerations rather than any consultation with fire specialists.^19511951 Marshall {Day226/96:25}-{Day226/97:24}. Diane Marshall told us that the guidance relating to ACM panels with polyethylene cores was open to being misread.^19521952 Marshall {Day226/81:22}-{Day226/84:7}. We do not accept that and we do not accept that the guidance note was a distraction from the tragedy at Grenfell Tower. On the contrary, it is of direct relevance to the attitudes of industry and NHBC at the time.

¶26.121 Diane Marshall responded to Mr Martin on 29 June 2017,^19531953 {NHB00001465/1}. the day after the guidance note had been withdrawn.^19541954 Marshall {NHB00003434/43} page 43, paragraph 201. She was aware it had been receiving media attention but disputed that she was concerned about the department's request for evidence.^19551955 Marshall {Day226/110:8}-{Day226/112:13}. We do not accept that the timing was coincidental. Enquiries from government were clearly instrumental in NHBC's decision to review its policy and withdraw the note. Indeed, Ms Marshall conceded that she was aware that no relevant ACM panels had ever been part of a successful test in accordance with BS 8414.^19561956 Marshall {Day226/119:9}-{Day226/120:12}.

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