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  1. Andrew, excellent work, once again. I think the comments by Dr. David Crowder and Brian Martin at the Lakanal enquiry are the clincher here, absolutely no doubt they are saying that external cladding panels only have to meet Class 0, not limited combustibility, or non combustibility.

    Of course the year after this, in June, 2014 we did have the announcement by the Building Control Alliance of Guidance Note 18, which restricted all materials in external cladding to limited combustibility, unless it passes BS 8414 by actual test or by newly introduced ‘desktop study’.

    The attempt to describe the core of the ACM panels as filler is a clear nonsense, fillers are a reference to building material fillers, whether cement, PE foam or bitumen based.

  2. Andrew, I thought you would be interested in this comparison of thermal conductivity (lambda values) of two types of insulation vs ACM cladding panels. It shows pretty conclusively that ACM rainscreen panels cannot be regarded as insulation material.


    Celotex RS5000 thermal conductivity is 0.021 W/mK

    Rockwool thermal conductivity is 0.035 W/mK

    ACM Rainscreen cladding panels

    Alucobond PLUS 3mm thermal conductivity is 0.49 W/mK

    Alpolic A2 and FR thermal conductivity is 0.45 W/mK

    Reynobond PE 4mm has a thermal conductivity of 0.44 W/mK

  3. Brilliant, thanks John for your understanding of ‘filler material’. Forgive my ignorance, but in what circumstances do they tend to be used in external wall construction? I suppose there might be a myriad occasions when one might want to fill in a gap or a hole for one reason or another, but I don’t have a clear picture of it.

    So I guess the effect of the 2006 amendment was a shift from PE foam and bitumen (and any other combustibles) to cement (and any other non-combustibles).


  4. I previously tried to post on here Andrew, but maybe got blocked for links- trying again. Fillers are simply used to fill cracks or gaps caused by movement or shrinkage/expansion or other damage to the masonry, occuring before or during the refurbishment process.

    As you say, the DCLG are very much trying to obfuscate here, there really is no controversy as to what filler etc. is in this meaning in the Approved Document B. If you search for watco or corden fillers you get an idea of the sort of product.

  5. Andrew, it’s possible that you could stretch that meaning to refer to filler or welding rods used in the welding of either metals or plastics. But still, it cannot be used in the sense of a fusion bonded core of a commercial product as in ACM or other composite panels such as VMZINC or Alpolic zinc/steel/titanium.

    I am not sure why I hadn’t noticed this before, but there is a section that explicitly refers to these ‘thermoplastic CORES’ and NOT ‘fillers’ in Appendix F (pg. 145) of Approved Document B Vol 2, but it mostly concentrates on the risk these pose internally, which is, in hindsight, clearly a bad judgement. There is also a section in Appendix B (pg. 120) part 18 that could refer to external panels:

    “A thermoplastic material in isolation can not be assumed to protect a substrate, when used as a lining to a wall or ceiling. The surface rating of both products must therefore reach the required classification. If however the thermoplastic material is fully bonded to a non-thermoplastic substrate, then only the surface rating of the composite will need to comply.”

  6. John, thanks very much for the information on fillers. The ones I have looked at – eg Watco putty, Watco Concrex, Corden’s Fibrefill, seem to be combustible, judging by the Material Safety Data Sheets. It would be interesting to find one which is advertised as suitable for use on external walls over 18 m.

    [ADDED 19 December 2017. I missed Corden’s Concrete Repair products, including Renderoc which is Euro Class A2: More or less traditional mortars with little or no organic content will generally be suitable I think.]

    Thanks also for pointing out Appendix F which as you say adds to the case that the ACM cores can not be described as filler material.


  7. John, with regard to your suggestion of 1 August that sealants are the et cetera, is this not ruled out by the first parenthesis in 12.7: ‘not including … sealants’?


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