ADB Requirements - Separation of Flats

[Northern Uproar]

In the 2000 edition of ADB, Table A1 states that the separation of flats should be as per the elements of structure. In the 2006 edition, this was reduced to whats in Table A2 or 60, which ever is less, so a building that required 90mins to the structure would have 60mins enclosing each flat.

Can anyone point me to the resons for this reduction - was there work done on fires suggesting that 60 mins is all that's required. The consluation docs released prior to the publication of 2006ADB don't seem to mention it.

[wee brian]

This was an approach that a lot of designers were adopting anyway and a lot of BCBs were happy to accept it.

The argument is that it makes no sense to ask for higher degree of seperation. 60 Mins will contain almost all flat fires. You will run out of fuel before the walls fail.

The elements of structure provisions incorporate a "consequence of failure" factor. So really tall buildings get a bit more as a tower block falling over is generally considered to be a bad thing.

[colin todd]

Is Elland House not a tower block then, Wee B?

[kurnal]

and a lot of BCBs were happy to accept it.

Tail wagging the dog.

 I wonder if the BCBs are fully considering much of what they approve or are they pandering to commercial pressure? I have lost much sleep this weekend pondering what to do about a 2 year old  10 storey mixed use city centre development where I was asked to carry out a FRA of the residential accommodation. Elements of structure should have been 120 mins reduced to 90  (fair enough its only 31m),  doors on protected shafts reduced to 30 mins- these brutes extend from retail to top of roof though dead end flat corridors. Trouble is they are not protected shafts - the base of the shafts rise unprotected from the retail storage and refuse areas, the worst being a 250 sq m wheely bin storage area with no ceiling.  

6 storey flats on top- 15 single staircase  cores that have no door discharging to fresh air at the bottom, but to the lowest level of flat corridor in a dead end condition with up to a 9 m unprotected corridor past flats and laundry to the final exit/ access for firefighters. No provision for ventilation on the lowest level  or on several upper levels either. Stay put strategy no detection or alarm in common areas or risers.
Top storey height 31 m but standard passenger lifts. I could go on at some length.

Design had an approved fire strategy written on several sides of A4 that did not mention any of the above.
Designed, built by a large National, approved by local authority BC and full consultation with fire authority. How on earth does this happen?

I have turned down two other projects recently. There seems to be a fashion for reducing the protection to firefighting shafts. There have been two proposals come across my desk in which firefighting access is being sacrificed for in favour of architectural aesthetics. In one multi storey hotel the firefighting lobby at one upper level was to be created using drop down curtains. In another access to the base of one of the fire fighting shafts was through the unprotected ground floor. This was to be approved on the basis that if the fire was on the ground floor access to the upper floors would not be required and that there was another shaft giving acess to the upper floors that could be used. The size of the building required two shafts.
When I turned the job down I was reminded that there are many other fire consultancies who will support and assist in pushing such schemes through.

Tail wagging the dog again? Because these buildings will be held up as icons of great design and may be used to further reduce standards when ADB is next reviewed?  

[CivvyFSO]

Kurnal

Sometimes things are built with consultation from the fire authority, but the fire authority have objected to specific parts all the way through. Building Control Authorities are often put in a position by the designers whereby if they oppose parts of a scheme the deveoper simply goes somewhere else for approval. The problem with firefighting shafts, as I am sure you are aware, is that once the BCO accepts it and it gets built, there is very little we can do apart from tut in disgust every time we think of it.

Not all BCO's fold as easy as this, but many (especially AI's) act like they are the fire engineer representing the client when it comes to discussions at meetings.

Another problem is that fire engineering makes it quite easy to pull the wool over people's eyes, and it is easy to 'prove' (read: "make it look like") almost anything is safe. This is predominantly how fire engineering is used, not to build particularly impressive buildings, simply to reduce standards for cost reasons. I am not saying that I expect everything to be over engineered, just that I don't expect the factor of safety to be shaved down time and time again leaving a building that is only safe providing they have the British Standard fire with a British Standard evacuation.