Proposed changes to building regs, limiting the use of timber

[saveasteading]

This from the Timber Development Association.

 

A number of changes have been proposed to Approved Document B – the UK’s statutory guidance on how to meet the fire safety requirements of the Building Regulations. These changes affect the use of combustible materials – including timber – in buildings. We welcome some of the proposed changes, but there are others that we strongly disagree with.

One change, for example, is to apply a height threshold of 11 metres upon any building containing timber in its elements of structure. Other changes require higher fire ratings for cladding, membranes and sheathing in external wall systems – which we consider disproportionate.

 

I haven't read it yet but will do., and will respond if I see the need... which seems likely.

Responses from individuals like us should have some weight as we have done it, or are about to do it.

 

I have had most of my career in steel, but strongly support timber where appropriate.

 

I've had a couple of run-ins with bco's on timber being 'combustible'. Even when completely encased in plasterboard, it is wood, and wood burns, so you can't use it, went the argument.

These are not flexible people and are becoming ever less so., so ambiguity and global statements must be avoided.

Plus I've met the sort of people who make these proposed reports and I wouldn't have given any a job. They tend  not to be practical or fully understand the whole issue.

 

In a domestic situation what is magic about 11m? as long as there is easy exit.

 

I expect this all follows Grenfell which is fair enough, but common sense may not prevail.

'Something has to be done'.  Pursue the guilty parties? Or reduce the use of a material which was not remotely implicated?

 

 

 

https://timberdevelopment.uk/approved-document-b-you-have-until-wednesday-july-1-to-submit-your-response/?utm_source=TDUK+Contacts&utm_campaign=2eb47531a6-Designer+Update_COPY_01&utm_medium=email&utm_term=0_4619f835bd-2eb47531a6-223169024

 

 

 

 

 

 

 

[SteamyTea]

29 minutes ago, saveasteading said:

what is magic about 11m

If one assumed that a window is at 10m, then the fall time is 1.43 seconds.

The velocity will be around 14 m/s (50 kmph).

An 80 kg (12.5 stone) person will impart 7845 J on impact, which is a force of 1.12 kN.

 

One could argue that the height should be lower.

 

It would be easier to draft legislation that says all building materials are non combustible (and fumes must be taken into account as well) and must still be rated at 150% of the elements designed capabilities after 2 hours of temperatures above 320°C.

That way, any material can be used, just that it has to be designed better.

 

I am a great believer that safety legislation can improve quality and reduce costs. Industry has never liked 'being told what to do', but they always step up and have creative solutions in the end.

 

[saveasteading]

36 minutes ago, SteamyTea said:

creative solutions in the end.

Good suggestion.

On a fire engineering course they explained how long a timber takes to burn through, as the outer faces first become charcoal which protect the core. Hence we see the skeletons of timber house fires, not a pile of ash.

And even in a bonfire a 4 x 2 will last a long time.

 

So are you suggesting that above 11m the whole structure gets more protection. Eg 1 hour fire protection gets 90 minutes?

[SteamyTea]

30 minutes ago, saveasteading said:

So are you suggesting that above 11m the whole structure gets more protection

No, to save any grey areas, confusion and builders/supplier being chancers, I am suggesting all materials used have to meet a set level of thermal/structural/failure safety standard.

There should e no opportunities for people to wriggle out of their civic duty.  I suspect this is what will happen when people start to get prosecuted for the Grenfell tragedy.  It every one knows some simple rules, then they are easy to follow.

[marmic]

I'm no expert but agree with charring - pretty sure CLT producers have test data too. (We would have liked to have used CLT on our almost completed build but was cost prohibitive - only for the rich on small projects!!).  So back to the point, I was working with an architect on a highly sustainable tall CLT building - probably about 5 years ago now. Possibly 10-12 storeys from memory? (my bit was just some specialist internal items). The whole design had to be changed as UK insurers wouldn't touch it, despite the type of structure being proven and used for many years in Nordic and central European countries. Probably same people jumping to conclusions and 'advising' insurers. Progress in the UK -  how dare we!

 

On a much smaller scale we needed to make a small claim on house insurance few years back in our previous home - I can honestly say the underwriters and so called surveyors sent out didn't have a clue. Same sort of people giving 'advice' no doubt. 

 

It's sometimes good to rant 

[saveasteading]

1 hour ago, marmic said:

It's sometimes good to rant

You speak sense.

Insurers know nothing other than statistics and minimising risk (theirs).

 

On the same course they advised that all the protection specifications are conservative. Eg a plasterboard manufacturer provides a wall panel for testing to half hour exposure, and it gets tested.  After half an hour the test is halted so as not to survive an hour and confuse us with the possibility that fire board or thicker boards  aren't needed for 1 hour.

 

Similarly whether any jointing at all is necessary for fire purposes.