On Grenfell's second anniversary, 60,000 Britons are still living in firetraps clad in the same deadly, decorative materials

[L0ki]

That makes sense. Thank you.

@Alistair_T

The significant issue is that the UK regs are entirely silent of spread of fire outside the building and back in,

I gather that will be/is an issue for the Inquiry.

Mr Todd (the Inquiry ‘legislation’ expert witness) takes the view that it is covered by Building Regs but it’s clearly a question of interpretation.

https://www.grenfelltowerinquiry.org.uk/evidence/colin-todds-expert-report

2.35 As it is likely that Requirement B4(1) will be relevant to the Inquiry, I draw the
attention of the Inquiry to the wording of that Requirement, namely “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”.

2.36 Interpretation of this Requirement rests on the meaning of the word
“adequately”. However, one intent of this Requirement is, in my opinion, to
minimize the potential for external spread of fire from one floor to another.

That all seems to be part of the current issue. People interpreting the requirements as best they can in the real world constraints of the available materials and budget and now being told - well, of course that system doesn’t meet the Regulations.

The whole report is worth reading for those interested in the legislative/guidance background.

[Alistair_T]

@L0ki

spread of fire over the
walls

Is also a key part of the interpretation, “Over” being different than “through” The approved documents say “Requirements of B4 will be met:
A. If the external walls are constructed so that the risk of ignition from an external source and the spread of fire over their surface is restricted”

Worth noting that the text you quoted above is the actual regulation. I mean that’s the entirety of it, other than a shorter sentence on roofs, the approved documents are simply guidance after that and can be dealt with in lots of different ways. Which is not ideal in such a contractually murky and complex industry.

[L0ki]

@Alistair_T

Is also a key part of the interpretation, “Over” being different than “through”

I think the logic is that compliance with B2 and B3 should deal with fire getting out (and presumably also back in). If proper compliance with B4 then prevents fire spreading across the outside of the building, then fires should be reasonably contained.

But yes, it is all down to interpretation; there’s nothing explicitly covering fire getting out and then back in elsewhere and the wording of B4 is as you say quite brief.

It does set up a nice get-out for the legislator though. “Ipso facto, your building did not comply with B4; since fire spread all over it, the spread of fire was clearly not ‘adequately’ resisted.”