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Grenfell Tower: was the cladding really banned material?

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So, was London’s Grenfell Tower, scene of a horrific fire that killed dozens of people, covered in “banned” flammable cladding?   The  answer – worryingly – is probably no. And if that is the case, it exposes the shocking flaws in Britain’s regulatory system for high-rise developments.

The Department of Communities in initially answering this question – before any tests were made on the actual material – said this: “Cladding using a composite aluminium panel with a polyethylene core would be non-compliant with current Building Regulations guidance. This material should not be used as cladding on buildings over 18m in height.”

But this is not the case. Such cladding – described officially as “material of low combustibility” (MOLC) is lawful and recommended above 18 metres, as is the more fire-resistant cladding described officially as “non-combustible”. Composite aluminium panel with a polyethylene core may well meet the standard as MOLC. So, as long as the suppliers didn’t do some sort of substitution with inferior stuff, such panels are lawful.

This is what the government Building Regulations Approved document B of 2010 vol 2 actually say:

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

This gives a hint of the rather vague regulatory framework that applies to materials in buildings – almost a statement of the obvious, leaving suppliers, builders and inspectors simply to do their best to ensure safety. As to cladding for high-rise blocks, the document goes on to say:

Insulation Materials/Products
12.7  In a building with a storey 18m or more above ground level any insulation product, filler material (not including gaskets, sealants and similar) etc. used in the external wall construction should be of limited combustibility (see Appendix A)

So this is where DCLG got it’s 18 metres from. But by no means is this a ban on the sort of material (probably) used on Grenfell Tower. Indeed “limited combustibility” is the standard for this sort of work. The guidelines do not even suggest using the higher standard “non-combustible” material. At B4 (1) (page 91), the document says:

“The external walls of the building shall adequately resist the spread of fire over the walls and from one building to another, having regard to the height, use and position of the building.”

The test used is to apply flames to the surface (not the polyethylene core) of the panels. Here is what a manufacturer of building materials (not those used on Grenfell Tower) has to say by way of explanation of the standard:

“It is important to note that a Surface Spread of Flame Classification does not infer [ie imply] any resistance to combustibility; it is solely a measure of the spread of a flame across the material’s surface.” (Rockwool Ltd, page 4).

Yet that is sufficient to meet the standard. It concludes that for the builder or developer: “The first and by far least restrictive option is to use materials of limited combustibility (MOLC) for all elements of the cladding system that are situated both above and below 18m.”

It is “least restrictive” because in effect it is pre-assessed as being acceptable for this sort of job: it reaches an “EN reaction to fire classification” of A2. Otherwise the developer would have to go through a process of getting clearance for the materials it wants to use from the independent testing body, UKAS (the BS8414 Test which would produce a report showing the BR135 specification has been met – see below.)

So above 18 metres “material of low combustibility” (MOLC) is standard. And, of course, “non-combustible” material could be used too (A1 on the reaction to fire classification). This is the material, that would, according to some news reports, cost only £2 a square metre more than the Reynobond PE aluminium with polyethylene core cladding apparently ordered for Grenfell  Tower.

Suppliers Omnis Exteriors said they were asked for Reynobond PE cladding, which is MOLC. This aluminium composite material (ACM) would have met the standard, designated “Class 0 rating for the surface spread of flame” and the A2 “reaction to fire classification” – accepted as suitable for this use.

Similarly the Celotex RS5000 infill lagging behind the panels, found to be flammable in new tests after the fire, is according to the manufacturers:

“a premium performance PIR insulation board that: Has been tested to BS 8414-2:2005, meets the requirements in BR 135 and the first PIR insulation suitable for rainscreen cladding applications above 18 metres in height; Features Class O fire performance”.

So the Reynobond PE is apparently legal (and presumably the Celotex is too, again on a “low combustibility” basis). But should it be? The material is lab tested for the effect of flames to its aluminium surface, not in situations when it might be broken through to the core or in high temperatures under which the aluminium would burn through.

It certainly should not be legal, according to Phil Barry, managing director of CWB fire safety consultants in Gloucestershire. who told the Guardian:

“We need to do full-scale tests to see how these materials perform in the real world. In a full-scale test, the outside sheet fails, and it exposes the plastic core, which then burns. That’s what causes the problem. We should be saying no combustible materials on buildings above 18m.”

This whole issue is complicated and no one should think that this post has got to the bottom of those complexities. But it is clear that thinking in terms of a cladding having been “banned” is wrong – and does not begin to address the full issues about Grenfell Tower and all the other such tower blocks with similar issues.

The regulations are composed in “risk to health and safety” terms rather than specifying what is safe and what isn’t. The safety of legal cladding has to be considered in the light of other issues: exits, fire doors, corridors providing (or failing to provide) escape routes, whether fire engines can get there – and the fact that the use people put the buildings to can easily undermine such safety precautions – or the extent to which vulnerable people are housed there. So it is significant that those decanted from Camden flats after the Grenfell Tower fire were asked to move because of suspect gas fittings and faulty fire doors rather than unsafe cladding.

MOLC may be deemed adequate and lawful but only in the context of other issues – creating a mountain of regulatory complexity which explains why tragedies like Grenfell Tower keep happening.

So the regulations (Part B) say:

“0.4 Whilst guidance appropriate to each of these aspects is set out separately in this document, many of the provisions are closely interlinked. For example, there is a close link between the provisions for means of escape (B1) and those for the control of fire growth (B2), fire containment and/or suppression (B3) and facilities for the fire and rescue service (B5) … Interaction between these different requirements should be recognised where variations in the standard of provision are being considered. A higher standard under one of the requirements may be of benefit in respect of one or more of the other requirements. The guidance in the document as a whole should be considered as a package aimed at achieving an acceptable standard of fire safety.”

The Grenfell Tower panels themselves may have been legal ie compliant with the relevant standard – but their use may not have been because of the context in which they were used. The condensation void between the lagging and the panels may have increased the intensity of the fire, for example; there is a suggestion that the creation of corner patterns using the panelling may have been problematic (similarly funnelling and intensifying the flames at that point perhaps?). Were window frames of the right standard? Were the cladding panels slotted together without separators that would have inhibited the flames? Are there sprinklers in place (the regulations added this in 2007: “Sprinkler systems should be provided in blocks of flats exceeding 30m in height”). Is there more than one set of stairs for escape? (In Grenfell Tower the answer is no.)

We can be pretty certain that what happened at Grenfell Tower was illegal – simply because of what happened at Grenfell Tower. It’s a circular logic. The regulations are outcomes-based rather than prescriptive – see 12.5 quoted above: the cladding “should not provide a medium for fire spread if it is likely to be a risk to health or safety”. We know something has gone horribly wrong – but it will be very difficult to establish who is to blame.

Twitter: alrich0660

Note. BBC’s World at One has now established that the Government has ordered that the new tests on cladding around the country should be interpreted to include the polyethylene core in determining whether they are made of “material of low combustibility”, not just the surface. Large numbers of the panels, perfectly legal until now (having passed under BS476), are failing this more rigorous test. (BBC WATO 26 June 2017 at 19.30 minutes.)

So this raises a significant financial issue: who should pay for removing what was legal cladding and putting up the new material: councils, who have paid millions to clad their buildings already? Tenants – many of whom will be right to buy long leaseholders who have also contributed to cladding previously – will they be stung for the upgrade too? Or the Government, which seems clearly to have botched the whole regulatory scheme from the offset?

Also: experts have criticised the new government tests that are failing huge numbers of cladding panels, which seem to involve simply setting fire to the polyethylene core and declaring it as failed because it burns (obviously). See the Guardian. The manufacturers of Reynobond PE have withdrawn the material from worlwide sale citing the inconsistency of regulatory regimes (the Guardian).

Here is a video of a British Standard test for BS 8414 fire performance: Fire test. Note that a whole panel is tested for the external spread of flame. The idea is to test whether a fire breaking out of an opening (such as a window) will result in excessive fire spread up the outside of the building with the fire re-entering at a higher level. The new tests seem to take a piece of the cladding 25 cm2 and burn it, including the exposed polyethylene core – which is why they have been criticised by the industry since they imply vast amounts of cladding will have to be removed..

• This piece from Reuters suggests the Reynobond supplied for Grenfell Tower wasn’t lawful for the building but notes:

“Some safety experts say the regulations are not black and white. The UK uses a ‘principles-based’ approach to regulation which puts an onus on companies to operate safely, based on common understanding of risks and the technology available. This differs to the highly specific ‘rules-based’ approach to regulation taken in the United States. Supporters of the principles-based approach say it avoids the emergence of loopholes and means companies have to take account of new information on risks immediately, rather than wait for a new regulation to be drafted.”

• However a useful piece from Building Design here notes:

“A building over 18m tall must use materials with a classification of B-s3 or better. This suggests both types of Reynobond panel would meet the requirements of Part B for the flammability of external cladding.”

It also says, though, that this is contradicted elsewhere in the regulations where it says over 18 metres it must have a higher rating – A2 or better – which it describes as non-combustible (rather than low combustibility).

• This item describes the European classification system.
This article from Probyn Miers gives a lot of detail on similar high rise fires. It notes:

“In the UK since 2006, under the Regulatory Reform (Fire Safety) Order 2005 (“FSO”), building owners, employers and occupiers have been legally obliged to evaluate fire risk in all buildings other than private dwelling houses.  The FSO is applicable to apartment blocks with common entries, staircases and landings.”

• This from University of Kent Countercurrents suggests social housing has become unmanageable.

Government standards: External fire spread
B4. (1) The external walls of the building shall adequately resist the spread of fire over the walls and from one building to another, having regard to the height, use and position of the building.

External walls
B4.i The construction of external walls and the separation between buildings to prevent external fire spread are closely related. The chances of fire spreading across an open space between buildings and the consequences if it does, depend on:
a. the size and intensity of the fire in the building concerned;
b. the distance between the buildings;
c. the fire protection given by their facing sides; and
d. the risk presented to people in the other building(s)

B4.ii: Provisions are made in Section 12 for the fire resistance of external walls and to limit the susceptibility of the external surface of walls to ignition and to fire spread.

B4.iii Provisions are made in Section 13 to limit the extent of openings and other unprotected areas in external walls in order to reduce the risk of fire spread by radiation

BR135 include the following:
■ External and Internal Fire Spread – determined by a 600ºC rise in temperature on the external/internal face of the building (measured at a point approximately one storey above the fire floor) for thirty seconds or more during the initial fifteen minutes of the test.
■ Mechanical Performance – determined by an assessment of building collapse, spalling, delamination, flaming debris or fire pool.


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