Chapter 59: Window reveals

Chapter 59: Window reveals

Introduction

¶59.1 The refurbishment of the windows at Grenfell Tower involved fitting new uPVC boards at the head of the window, the sill and the jambs (often referred to as the "window reveals"), in each case over a 25mm layer of insulation.^22412241 Phase 1 Report, Volume I, paragraph 6.28. After the fire, the insulation that had been used was identified as either Celotex TB4000 or Kingspan Thermapitch TP10.

¶59.2 In his Phase 1 report the chairman concluded that the window reveals had provided a route for fire to spread from the interior of Flat 16 into the cladding. He found that the fire had probably entered the cladding as a result of hot smoke impinging on the uPVC window surrounds causing them to deform and fall away, together with the insulation which was attached to them. That created a gap which allowed the fire to gain access to the cavity behind the ACM panels and ignite combustible materials.^22422242 Phase 1 Report, Volume IV, paragraph 22.38. In Chapter 110 we have reconsidered that conclusion in light of the evidence provided by BRE reconstruction evidence but we consider that it remains sound. In this chapter we examine how those materials came to be present around the windows.

The original specification

¶59.3 In the NBS Specification Studio E specified plywood window reveals^22432243 National Building Specification (NBS) {SEA00000169/249} clause 240. It also stipulated that the fire-rating for the window reveals should be "fire-rating Class 1 or Class C-s3, d2". together with "compressible insulation in gaps".^22442244 National Building Specification (NBS) {SEA00000169/243} clause P10. The compressible insulation was specified as mineral wool to BS EN 13162 manufactured by Rockwool.^22452245 National Building Specification (NBS) {SEA00000169/243} clause 191. (Mineral wool is inorganic and non-combustible.)^22462246 Bisby, Phase 2 Experiments Work Package 2 {LBYWP200000001/36} paragraphs 239-240. However, Studio E did not specify precisely which gaps were to be filled with mineral wool and the tender drawings did not do so either,^22472247 {SEA00002499}. although they should have.^22482248 Crawford {Day9/149:15}–{Day9/150:11}; Hyett, Module 1 Report {PHYR0000029/80-82} paragraphs 4.3.94, 4.3.96 and 4.3.98.

The substitution of uPVC for plywood

¶59.4 Although the NBS Specification provided for the window reveals to be constructed of plywood, Harley proposed the substitution of uPVC boards as part of Rydon's value engineering exercise.^22492249 {RYD00003316}. Neither Harley nor Rydon appears to have given any consideration to the relative fire performance of the two materials.^22502250 Dixon {Day44/171:24}-{Day44/172:5}. In general, plywood could be expected to provide a greater degree of fire resistance than uPVC, which softens and deforms at temperatures above 60°C.^22512251 Torero, Phase 1 Report {JTOS0000001/41} Figure 9; Dixon {Day 44/170:12-21}.

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¶59.5 Simon Lawrence of Rydon originally expected Harley to undertake the package of works that included the replacement of the window reveals,^22522252 Lawrence {Day25/39:22}-{Day25/40:8}; Berry {OSB00000091/10} page 10, paragraph 16 (b); Berry {Day44/14:15-18}. but that package was removed from the scope of Harley's works when Rydon needed to find savings in its price for the work as a whole.^22532253 {RYD00086654/1}; Lawrence {Day25/39:22}-{Day25/40:8}; Berry {OSB00000091/10} paragraph 16 (b); Berry {Day44/14:15-18}. Accordingly, Harley's detailed drawings of the window arrangements showed that the fitting of insulation around the windows would be undertaken by others.^22542254 {SEA00003040/5}; {SEA00003040/7}.

¶59.6 On 16 January 2015, Neil Crawford reviewed Harley's drawing dated 13 January 2015 showing the details of the window design,^22552255 {SEA00003040/7}. which he accepted as conforming to design intent. He was not concerned that the drawing did not specifically indicate mineral wool around the windows because, as he told us, he knew that fitting the insulation was not part of Harley's work.^22562256 Crawford {Day11/98:5}-{Day11/101:1}. However, he failed to take any steps to deal with the fact that there was no detailed drawing at all, whether by Harley or Studio E, which showed mineral wool around the windows in accordance with the specification. He had no explanation for that omission, which drew criticism from Mr Hyett. Mr Hyett's opinion, with which we agree, was that, in accordance with its contractual obligations,^22572257 Deed of appointment between Rydon and Studio E {RYD00094228/11} items 31(a)-(c). Studio E should have produced 1:5 drawings which showed in detail how the voids around the window linings would be packed with insulation and what materials were to be used.^22582258 Hyett, Module 1 Report {PHYR0000029/82} paragraph 4.3.96.

¶59.7 On 12 March 2015, Jason North, Rydon's site manager at the time, asked Neil Crawford where he could find details of the insulation behind the fixed panels at the side of the windows.^22592259 {SEA00012940}. Mr North was referring to the gap between the larger window infill panel (panel P1) and the concrete spandrel of the original building.^22602260 Crawford {Day11/104:21}-{Day11/105:2}. Mr Crawford did not respond to that request, but he told us that he thought he had directed Mr North to Studio E's 1:20 drawings.^22612261 Crawford {SEA00014275/41} page 41, paragraph 118. However, those drawings did not show any details of the insulation around the windows and therefore it is unlikely that he did so.^22622262 Hyett, Module 1 Report {PHYR0000029/82} paragraph 4.3.98. Bruce Sounes' evidence was that the scale of those drawings did not permit references to the type of insulation to be used in these applications: Sounes {Day21/120:16-19}.

¶59.8 The refurbishment of the window reveals was not part of Osborne Berry's work,^22632263 Berry {OSB00000091/10} paragraph 16 (b); Berry {Day44/14:15}-{Day44/16:25}; Osborne {Day43/174:3-17}. which was limited to the removal of the original glazed windows to enable the new double-glazed window units to be installed.^22642264 Berry {Day44/15:22}-{Day44/16:7}; {Day44/18:17-21}.

¶59.9 By 23 February 2015 SD Carpentry Ltd had produced for the show flat (Flat 145) an example of the window reveals showing how they were intended to appear. Various companies, including a company called SD Plastering Ltd, looked at the finished example in order to decide whether to bid for the refurbishment of the window reveals.^22652265 Dixon {Day44/102:25}-{Day44/103:4}; {RYD00032519}. (SD Plastering was a construction company predominantly engaged in dry-lining work and was unrelated to SD Carpentry.)

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¶59.10 SD Plastering had already been engaged to carry out remodelling work on the lower floors of Grenfell Tower when Rydon approached it to undertake the refurbishment of the window reveals.^22662266 Dixon {Day44/99:19}-{Day44/100:14}; Dixon {SDP00000196/3} page 3, paragraph 13. On that basis we consider that Mark Dixon's estimate that SD Plastering became involved in these works in April-May 2015 is incorrect. (A director of the company, Mark Dixon, had previously been employed by Rydon.)^22672267 Dixon {Day44/95:3-23}. He knew Simon Lawrence, Simon O'Connor, Daniel Osgood and David Hughes, Dixon {Day44/97:21}-{Day44/98:24}. The first email correspondence in respect of the work occurred in February 2015;^22682268 {RYD00032519}. a progress report by Rydon dated March 2015 referred to SD Plastering's involvement.^22692269 {RYD00035207}.

¶59.11 Although it had not done work of that kind before,^22702270 Dixon {Day44/119:3-10}; {Day44/152:6-10}. SD Plastering ultimately undertook all the work to the window reveals, including the packing of gaps behind the uPVC boards with insulation,^22712271 Dixon {Day44/157:6}-{Day44/164:22}. apart from putting foam insulation into a small gap at the sides of the window jambs next to the columns.^22722272 Dixon {Day44/172:7}-{Day44/173:8}. See this gap highlighted in red bubbles in Lane, Phase 1 Report {BLAS0000009/13} Figure 9.9 9.10. We have not been able to determine which company or individual was responsible for that.^22732273 Osborne Berry said it did not carry out that work: Osborne {Day43/171:13-18}.

SD Plastering's contract

¶59.12 Although SD Plastering had a formal contract with Rydon for the dry-lining work,^22742274 {RYD00031801}; {RYD00031811}. there was no formal contract between them for the work on the window reveals. On 17 February 2015, Adam Marriott of Rydon sent Mark Dixon in connection with the dry-lining work a copy of Rydon's standard terms,^22752275 {RYD00031806}. which required all workmanship to comply with manufacturers' and suppliers' instructions and recommendations and current British standards and codes of practice.^22762276 {RYD00031806/4} paragraph 2.18.1. Mark Dixon understood that SD Plastering was required to comply with the same terms and conditions when carrying out the work on the window reveals.^22772277 Dixon {Day44/137:17}-{Day44/139:4}. Mr Dixon accepted that the work had to comply with any relevant standards and it follows that it had to comply with the Building Regulations in general and functional requirement B4(1) in particular.

¶59.13 Under the contract between Rydon and the TMO, it was Rydon's responsibility to co-ordinate and complete the design of the window reveals, which included selecting the goods and materials to be used and setting the standards of workmanship.^22782278 {RYD00094235/63} clause 2.1.1; {RYD00094235/69} clauses 2.17.1-2.17.12. Rydon was also responsible for co-ordinating and supervising the work of its subcontractors, including SD Plastering. Rydon's responsibility extended to monitoring its work and providing it with the information necessary for it to do the work.^22792279 {TMO10041791/128} part 2A/44, section A32, paragraph 110. Rydon ought therefore to have provided SD Plastering with a copy of the relevant part of the NBS Specification identifying the materials to be used, and ought to have provided it with Harley's drawings relating to the work, as accepted by Studio E.

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¶59.14 Under its contract with Rydon Studio E was responsible for developing the design of the window reveals, advising on the appropriate method of construction, selecting materials and co-ordinating any design work undertaken by SD Plastering.^22802280 {RYD00094228/9}; {RYD00094228/10}.

Design of the window reveals

¶59.15 In February 2015 a meeting took place between Rydon and SD Plastering in the show flat, during which Simon Lawrence told Mark Dixon that he was not happy with the window reveals because, among other things, the sill was prone to bowing.^22812281 {RYD00032519}; Dixon {Day44/106:3-8}; Dixon {SDP00000196/4} page 4, paragraph 17; Dixon {Day44/108:20}-{Day44/110:2}; {RYD00042486/2}; Lawrence {Day25/49:5-12}; {RYD00042487}. It appears that Mr Dixon made some suggestions for improving the design and that Mr Lawrence asked for a quotation for the work.^22822282 Simon Lawrence's email of 23 February 2015 {RYD00032519}. In the event, Rydon instructed SD Plastering to produce an alternative design for the window reveals that was more aesthetically pleasing than the example, easy to install and which remedied the problem with bowing.^22832283 Dixon {SDP00000196/4} page 4, paragraph 19; Lawrence {Day25/56:1-5}; Dixon {Day44/116:18}-{Day44/117:12}.

¶59.16 At some time between February and 6 May 2015 there was another meeting in the show flat to discuss the design of the window reveals. Mark Dixon attended, together with Simon O'Connor, Daniel Osgood and James Clifton of Rydon.^22842284 Dixon {Day44/107:7-25}; Osgood {RYD00094212/2} page 2, paragraph 8. At that meeting Rydon and SD Plastering decided to use a rigid insulation board to fill the gaps behind the uPVC boards.^22852285 Lawrence {Day25/56:10}-{Day25/58:7}; {Day25/62:3-7}; Cole {SDP00000220/3} page 3, paragraph 14; Dixon {Day44/112:12-18}; {Day44/112:19}-{Day44/114:15}. However Rydon did not tell SD Plastering what materials to use or provide it with any drawings of the window reveals.^22862286 Dixon {Day44/117:22}-{Day44/118:4}. In effect, Mr Dixon was simply asked to reproduce the effect of the work in the show flat but with a better finish.^22872287 Dixon {Day44/119:25}-{Day44/120:13}; {Day44/171:15-19}.

¶59.17 SD Plastering initially tried to use plasterboard or ply packing pieces underneath the windowsill to bridge the gap and to prevent it from bowing but were unable to secure them in place. Mr Dixon said that Celotex rigid insulation board was chosen instead to achieve a better fit.^22882288 Dixon {Day44/123:1-6}; {Day44/182:23}-{Day44/183:10}.

¶59.18 On 6 May 2015, Mark Dixon gave Rydon a quotation in which he described the work to be carried out.^22892289 {RYD00088957}. After removing the existing timber structure^22902290 Dixon {Day44/125:10-21}. a plasterboard backing was to be applied, after which Celotex insulation would be fitted to the head, jambs and sill. Mr Dixon's intention was to use either plasterboard or Celotex 25mm insulation board or a combination of the two to cover the gaps around the windows.^22912291 Dixon {Day44/128:6-12}. The Celotex board was expected to achieve the correct fit, act as a support to the uPVC and confer a thermal benefit.^22922292 Dixon {Day44/127:14}-{Day44/128:4}. He said the quotation had been drafted in such a way as to give SD Plastering flexibility about which materials to use.^22932293 Dixon {Day44/126:15-20}. In the event plasterboard was not used at all.^22942294 Dixon {Day44/125:3}-{Day44/127:7}; {Day44/185:1-6}; {Day44/196:16-20}.

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¶59.19 Neither Simon Lawrence nor Simon O'Connor read the quotation and neither could recall any discussions about it. Mr Lawrence knew that some sort of rigid insulation board was being used around the windows, but not necessarily that it would be made by Celotex.^22952295 Lawrence {Day25/36:7}-{Day25/38:15}; O'Connor {Day26/212:17-22}.

¶59.20 SD Plastering was never shown the NBS Specification relating to the work on the window reveals, nor was it given any instructions about the materials to be used in the gaps around the windows.^22962296 Dixon {Day44/167:20-21}. It was not provided with any architectural drawings relating to the window reveals and did not discuss the design of the work or the products to be used with Studio E.^22972297 Dixon {Day44/133:14}-{Day44/134:9}. Neil Crawford was not told that PIR and phenolic insulation had been used to fill voids around the windows. He was not shown the work or asked to comment on it during his site visits.^22982298 Crawford {Day11/106:10}-{Day11/107:7}. There was no formal process within Rydon for approving the materials used around the windows.^22992299 Lawrence {Day25/61:19-25}-{Day25/62:7}.

¶59.21 Mark Dixon said that he would ordinarily have expected to receive more information from Rydon about the products to be used on work of that kind, but he does not appear to have asked for any.^23002300 Dixon {Day44/131:14-17}. SD Plastering did not itself produce any drawings relating to the work.^23012301 Dixon {Day44/135:12-15}.

¶59.22 Neither Simon Lawrence nor Simon O'Connor examined the NBS Specification to see whether any insulation product had been specified for use in connection with the window reveals. Both accepted that they should have done so, although Mr Lawrence said that the Rydon site managers should also have paid closer attention to that.^23022302 Lawrence {Day25/45:1-22}; O'Connor {Day26/213:22}-{Day26/214:16}. If Rydon had looked at the NBS Specification it would have been obvious that the use of a rigid combustible insulation board was contrary to what had been specified.^23032303 Lawrence {Day25/47:12-22}. Rigid combustible insulation boards were not a comparable substitute for compressible and non-combustible mineral wool.^23042304 Lawrence {Day25/45:23}-{Day25/46:21}.

Compliance of the design with the Building Regulations

¶59.23 Pursuant to functional Requirement B4(1) and if following the guidance in Approved Document B any insulation materials used in the external wall had to be of limited combustibility.^23052305 Lane, Phase 1 Report {BLAS0000011/66-67} Table 11.10; see paragraph 12.7 of Approved Document B at {CLG00000224/96}. In addition, pursuant to functional requirement B3(4) the building had to be designed and constructed so that the unseen spread of fire and smoke within concealed spaces in its structure and fabric was inhibited. The need for compartmentation and the risk of fire spread around openings was highlighted in sections 8 and 9 of Approved Document B.^23062306 {CLG00000224/73} section 8; {CLG00000224/83} section 9, see in particular paragraph 9.3 which specifically warns about fire spread around openings. Rydon ought to have instructed SD Plastering that any insulation used around the windows was to be of limited combustibility or better and should have made sure that insulation of that kind was used. It did neither of those things, however. There was no discussion between Rydon and SD Plastering about how the choice of material to fill the gaps around the windows might affect fire safety generally.^23072307 Dixon {Day44/114:16-23}. Neither SD Plastering nor Rydon gave any consideration to the fire performance of the materials used to fill the gaps around the windows^23082308 Dixon {Day44/149:10-12}; {Day44/152:12-23}; {Day44/170:1-4}; {Day44/176:12-15}; O'Connor {Day26/207:17-22}; Osgood {Day30/181:25}–{Day30/182:12}; Cole {SDP00000220/4} page 4, paragraph 23; Dixon {Day44/152:1-5}. and it does not appear to have occurred to either of them that putting combustible insulation around the windows might affect fire safety.^23092309 Dixon {Day44/118:25}-{Day44/119:2}; {Day44/131:19-25}; {Day44/149:13-16}.

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¶59.24 Mr Lawrence accepted that Rydon had been responsible for ensuring that the products selected for the work complied with the Building Regulations and that it should have checked the choice of materials with Studio E.^23102310 Lawrence {Day25/63:12-18}; {Day25/61:6-9}; {Day25/63:23-24}. However, neither he nor anyone else at Rydon gave any serious consideration to whether the construction of the window reveals was likely to result in a breach of the Building Regulations.^23112311 Dixon {Day44/153:14-19}; O'Connor {Day26/207:23}-{Day26/208:2}; {Day26/209:12-18}. He admitted that he had not been aware that the Building Regulations might be relevant to the work on the window reveals;^23122312 Lawrence {Day25/62:18-24}. he had thought that they were not part of the building envelope and were therefore unregulated.^23132313 Lawrence {Day25/60:11-21}; {Day25/62:25}-{Day25/63:9}. Mark Dixon was also unaware that the Building Regulations might be relevant to the work.^23142314 Dixon {Day44/142:23}-{Day44/143:3}; {Day44/144:24}-{Day44/145:24}. He was not aware of the guidance in Approved Document B that insulation materials used in the external wall should be of limited combustibility.^23152315 Dixon {Day44/145:25}-{Day44/146:3}.

The supply and fitting of the insulation

¶59.25 SD Plastering purchased Celotex TB4000 insulation boards from Travis Perkins Trading Co. Ltd. When it became difficult to obtain supplies of Celotex, it obtained Kingspan Thermapitch TP10 insulation boards from a company called CCF Ltd.^23162316 Dixon {Day44/147:25}-{Day44/148:12}; {Day44/141:17}-{Day44/142:14}. Mark Dixon told us that he had assumed that that was permissible because the boards were being used only to bridge the gap around the windows and provide support for the uPVC window reveals.^23172317 Dixon {SDP00000196/7} page 7, paragraph 32.2. Mr Dixon could not recall any discussions with Rydon about whether Kingspan boards could be substituted for Celotex, but he thought that he had made Rydon aware of the substitution at some point,^23182318 Dixon {Day44/156:17-22}. and we think it likely that he did so.

Supervision of the work

¶59.26 Daniel Osgood was a site manager for Rydon until July 2015 and was responsible for supervising SD Plastering's work on the window reveals.^23192319 Osgood {Day30/172:19-22}; {Day30/198:11-13}. He did not discuss the need to maintain compartmentation or the risk of fire spread around the windows with anyone else in Rydon;^23202320 Osgood {Day30/175:5-23}. he just assumed that everything that was being used was "100% fireproof".^23212321 Osgood {Day30/183:8}-{Day30/184:3}. He could not recall having reviewed the NBS Specification^23222322 Osgood {Day30/183:22}-{Day30/184:3}; {Day30/184:23}-{Day30/185:12}. and assumed that Rydon had sent it to SD Plastering.^23232323 Osgood {Day30/187:23}-{Day30/188:4}. He did not recall having noticed the use of Celotex insulation in SD Plastering's quotation.^23242324 Osgood {Day30/188:25}-{Day30/191:5}.

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¶59.27 Gary Martin took over from Daniel Osgood as Rydon's site manager in July 2015 and became responsible for inspecting the work on the window reveals before the uPVC surrounds were fitted.^23252325 Dixon {Day44/215:7-20}; Martin {Day30/43:4-18}; {Day30/44:23}-{Day30/47:5}; {Day30/48:15-19}; {Day30/34:21-23}. He said in his witness statement that SD Plastering had been fitting a fire resistant seal between the window unit and internal sill and that a "fire barrier" was fitted around the window void so there was no gap between the window unit and inner concrete sill.^23262326 Martin {RYD00094216/1-2} pages 1-2, paragraph 6. However, that turned out to be merely an assumption on his part. When he was shown the photographs of the internal window reveals during his oral evidence it became clear that what he had assumed to be a fire-resistant seal or a fire barrier was in fact the aluminium foil on the insulation boards that he had seen during his site visits.^23272327 Martin {Day30/26:6}-{Day30/29:19}; {Day30/33:8}-{Day30/34:20}.

¶59.28 Mr Martin was not aware that combustible insulation had been used around the windows^23282328 Martin {Day30/26:14}-{Day30/27:2}. and had not seen SD Plastering's quotations, both of which referred to Celotex insulation being fitted in that location.^23292329 Martin {Day30/37:8-18}. He knew that insulation was being used but did not notice any branding on it at the time.^23302330 Martin {Day30/37:20}-{Day30/38:13}; {Day30/52:23}-{Day30/53:4}. He did not communicate any instructions to SD Plastering about the need to preserve compartmentation, the materials to be used, or fire safety generally.^23312331 Martin {Day30/38:22}-{Day30/39:14}. As far as he understood it, SD Plastering was reproducing the example provided in the show flat.^23322332 Martin {Day30/39:14-15}.

¶59.29 Neither Rydon nor SD Plastering knew that Celotex TB4000 was a European Class F product or that Kingspan TP10 was European Class E and that their fire performance did not therefore correspond to the guidance in Approved Document B,^23332333 Lawrence {Day25/62:9-14}; Dixon {Day44/153:20-22}; {Day44/154:25}-{Day44/155:5}; Osgood {Day30/188:12-21}. which called for products of limited combustibility (European Class A2).^23342334 Lane, Supplemental Phase 1 Report {BLAS0000011/60} paragraph 11.15.18; Hyett, Module 1 Report {PHYR0000029/141} paragraph 4.4.149.

¶59.30 Since it is likely that the failure of the window reveals played an important part in allowing the fire to escape into the cladding, we think we should summarise the factors that in our view contributed to their inadequate performance. First, Studio E should have produced detailed 1:5 scale drawings clearly identifying the insulation referred to in the NBS Specification and showing where it was to be placed. Next, Rydon should not have accepted Harley's suggestion that uPVC boards, with poorer fire resistance, should be used for the window reveals in place of plywood just to cut cost, because there was a significant difference in fire performance. Next, Rydon should have sent the NBS Specification to SD Plastering or should at least have given it instructions about the fire performance of the materials to be used in the window reveals. It should not have allowed combustible Celotex or Kingspan insulation to be used instead of the mineral wool insulation specified by Studio E to be fitted around the windows. Finally, neither Rydon nor SD Plastering gave any consideration to the fire performance of the insulation or the construction of the window reveals as a whole, which was unsuitable for its purpose.

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