Timber Framed Buildings

[Golden]

I've just seen the BBC report on the new build in Hackney and would like to hear your thoughts on this type of construction and the builder's comments regarding fire properties.

http://www.bbc.co.uk/news/uk-15298896

I've also just seen this report as a little bit of research after seeing the video; once again your thoughts are welcome. I've no vested interest in this subject but timber frame is moving rapidly into the mainstream and there are many arguments discussions to be had on the subject.

http://dev.uktfa.com/blog/2011/07/25/the-uktfa-demands-the-withdrawal-of-the-riscauthority-report-bdm14-%E2%80%93-fire-in-timber-frame-buildings/

[CivvyFSO]

Just because wood protects itself with char doesn't mean that there will be enough of a cross-section left to support the building, especially if the loading is suddenly altered to due to a sudden weakness elsewhere. The engineered joists which are normally used for floors/ceilings have no sacrificial layer of timber, so the rapid loss of some of these could dramatically alter the loading direction on any main structure. However, the wood should primarily be protected by something else (probably good old plasterboard walls/ceilings) and it SHOULD only be someone interfering with this (Or good old poor workmanship) which causes a risk.

Only time will tell, and my money would be on one coming completely down at some point in the future. It may take quite a long time and I am sure that there will be an underlying reason such as interference or workmanship. (I do suspect that there would not be much evidence left to look at to come to a decision, but that is what will be offered in explanation) Depending on the frequency or severity of such an event statistics may show that it is actually an 'acceptable' risk to society. However, that would be no consolation to any relations of people who might perish in such a building.

Another viewpoint is, if it suddenly means that more people can afford their own homes, live in nicer homes, and therefore have more pride etc, the knock on could be a slightly happier society which may manifest itself in less crime/suicides etc.

[Phoenix]

I think Civvy's prediction will probably come true at some stage, I feel a little uneasy about these buildings.  

Regarding the second link, I had to leave a comment at the bottom of that, which was:

"Whilst making no judgement on the actual performance of timber framed buildings in fire, as a trained statistician I have to agree with the objection to the published document (BDM14). The conclusions it draws are not supported by the evidence presented and the summary and the conclusions are peppered with misleading statements.

For example, in the summary it states, “fires in unprotected wood frame buildings account for over half of all fire fatalities in the US.” On the face of it this is quite a damning statement when considering the use of timber framed buildings and I would judge that it has been presented with this precise objective in mind. But it states elsewhere that 90% of all buildings in the USA are timber framed. Well, it doesn’t take a genius to realise that if 90% of all buildings are timber framed and if the risk from fire is equal in timber framed buildings and in buildings constructed in other ways, then we would expect 90% of fire fatalities in timber framed buildings. The fact that the document refers merely to “over half of all fire fatalities” implies that less than 90% of fire fatalities are in timber framed buildings. This is a good result for timber framed buildings as anything less than 90% means they have less fire fatalities than other forms of construction on a pro rata basis.

The UKTFA post, above, alludes to this and other similar mistakes when it states that a professional statistician would have drawn completely opposite conclusions from the data. But the author of the above post knows that this isn’t quite true because the whole analysis in BDM14 is undermined, as stated in the above post, by the fact that the document is based on an assumption that correlation implies causality. Assuming this is an assumption that there are absolutely no other variables that should be taken into account (i.e. that fire fatality numbers are solely dependent upon the construction materials). I would suggest that there are many, many other variables that should be taken into account (this is a completely different nation, a completely different geography and a completely different culture) and I would observe that the document BDM14 appears to have ignored these.

The document BDM14 is vacuous, naive and, worst of all, misleading. I have no axe to grind and no motivation other than a desire to see the true facts properly presented. I am a fire safety professional and would like to be able to make good judgements on timber framed buildings but document BDM14 is a distraction and an obstacle to the truth and I agree that it should be retracted."


Stu

[Golden]

I believe the response by the UKTFA is as flawed as the original document and that further serious research needs to be carried out into all types of timber framed buildings before we go any further up. I am no expert statistician but I do know that you should compare like with like; I think there has been a bit of a knee jerk reaction to the lack of care exercised on some building sites resulting in some spectacular crib fires. Having said that I do know of a four storey timber framed and occupied building that collapsed inwards during a fire that started and remained for a long while within the external cavity.

My concerns are for the building a few years hence when its been chopped about by various trades and amateurs, I'm also not sure how the brick facing is secured to the building and would be concerned from an operational perspective that this may come off suddenly in a fire situation. There are other operational issues that would need to be explored by UK brigades and learning from other nations that have been building with timber for longer.

We have all learnt about the behaviour of wood in a fire situation and the effects of charring, either in recruit training or at college. I would like to know what type of testing has been carried out on the structural members and how their behaviour in fire compares to a solid wood member of the same dimensions, are the test methods scrutinised or is this a case of the industry funding the tests and getting the results they paid for? Loadings within a beam for instance will change dependent on the charring and stresses will vary throughout the duration of the burn; something that I would find very difficult to replicate in test conditions.

I only posted this subject to gauge some opinions and help form my own opinions - I'm currently quite firmly sat on the fence on this subject with a slight leaning towards the sceptical side. My only conclusion so far is that there isn't enough quality research that has been carried out on which to base my opinion!

[Phoenix]

You might want to skootch along that fence a little to make room for all the other undecideds (including me).  My objection to the FPA document BDM14 is purely on statistical grounds.  It is erroneous and is an obstacle to establishing a fuller understanding.

I feel that the problem with these buildings may lie in the presence of the cavities and their vulnerability more than with the nature of the structural elements.

Stu