High rise flats / Building regs

[Meady]

This is a theoretical query as I'm doing some training and high rise blocks of flats has come up (not specific to Grenfell as the paper was written before the tragedy in 2017).  The paper tells me to read ADB and BS9999 as well as the DCLG/GOV.COM guide for purpose built flats.

I have been told by someone else in the industry (which is why i am querying this) that Grenfell complied with current building regs...I am a novice in the industry but find it hard to get my head around why a building which is 30m+ high would only have one means of escape (even with a stay put policy)?!?!?  

So, I have read what I thought would be the building regs (ADB 2010) to see what the current guide would be; but I cannot for the love of me find where it says in the ADB that a single stair is acceptable in a high rise block of flats?! Please can you steer me in the right direction??

Article 2.19 and 2.20 to me reads that a single stair is only allowed up to floor levels of 4.5m?? I've read it time and time again and am just getting more and more confused!  Is this now right and any block of flats with a floor above 4.5m must now have at least two means of escape once occupants are out of their flats and in the shared corridors?

Any help always appreciated.  My only thought was that, at the time of design and construction, Grenfell did conform with the building regs. and that the current ADB is not retrospective.  Also, would the FSO 2005 see it as unreasonable/unpractical to install a second means of escape afterwards??

Sorry - lots of questions here...but any guidance would be much appreciated.

[AnthonyB]

Grenfell was built in the 70's and complied with Building Regulations at the time (which referred to CP3 chapter lV part 1 as the standard to follow).0

It was refurbished in the mid 2000's and the alteration work (only - not the whole building) was subject to the Building Regs and the then current edition of Approved Document B. It is argued that the cladding installation complied with ADB.

You can still build a high rise single stair block of flats, I've dealt with a few. This is because whilst the Building Regulations are law they only set broad functional aims. Approved Document B is not statutory and is only one way to meet the functional aims in the regulations. You can use alternative solutions as long as they can be demonstrated to give the equivalent level of safety. This could be by using BS9991 (BS9999 is not for flats, only certain commercial buildings) or a bespoke engineered solution using BS7974 fire engineering principles.

One of the high rises I refer to, built in the 2000's, has a single stair with extended corridor distance and also non standard open plan flat layouts as it uses residential sprinklers to each apartment and a purpose designed mechanical smoke control system to the corridors. 

Building regs are not retrospective and so existing single stair high rises are perfectly acceptable, with thousands of fires in these over the decades not making the news because they stay in the flat of origin.

It's very likely if the flat of fire origin occurred in a non refurbished Grenfell we may not have read about it other than in local press as you would only have the original non combustible concrete fascia.

 

[Tom Sutton]

Further to what AB has said check out 2.20 of the ADB vol 2.and Diagram 7.

[Meady]

Thank you Anthony and Tom again for your help - that's brilliant.

Tom - thank you for pointing that out. 

I may be misreading this...but a note under ADB paragraph 2.19 states 2.20 to 2.51 are not applicable where the top floor is not more than 4.5m above ground level...so the fact there is a double negative in that sentence, does that mean that 2.20 to 2.51 are applicable only to buildings where top floor is higher than 4.5m???  I am guessing that 4.5m would be a single or two storey dwelling so these guides are not relevant to lower level flats??

[Tom Sutton]

That's how I interpret providing the lower level flats meet the standards of 2.11 and 2.12.

[Meady]

Excellent - thank you again for your help.