Anomoly in BS 5588 part 6

[Firemac]

I am a fire prevention officer. i am assessing a proposal of a extension to a public assemby/theatre occupany type building. The basis of compliance with B1 is B.S. 5588 Part 6. Part of the proposal incorporates a single stairs which serves a floors up to a  height of 20 metres. These floors are used for storage, dressing rooms, general ancillary accomadation. The travel distance is within limits and there will be less than 50 persons per storey. The rooms are lobbied at every level. Conventional wisdom (other codes of practice: TGDB, BS5588 PArt 11) would require a second stairs for floor over a height of 10 metres.  However B.S. 5588 Part 6 seems to place no restriction on the height of a storey served by a single stairs. The limiting factor seems to be travel distance and occupancy/storey. I think this is just an anomoly that the code never envisioned as it was written for a public assembly building that would cater for a large amount of people where 50 or less on a storey would not have been a practical consideration. I feel the architects has just found a loop-hole in the code of practice. There is no fire engineering alternative solution proposed either. Any comments would be great.

Regards

[jokar]

I think that is incorrect, if you read clause 6.4.2. it states that you need at least 2 storey exits for 1 to 600 people.

[kurnal]

Just out of interest how many floors are served by this staircase? Is it that there is one floor very high up say  on a  fly gallery above a stage or is it a multi storey building?

[Firemac]

There are 7 floors being served by this single stairs. There is also a gantry and rooftop services but they do have alternatives escape. The rooms are fully enclosed and not open such as a mezzanine. I should have been more specific.

In regards to section 6.4.2 it also states that a "single escape route is acceptable in the case of a room not comprising a whole storey accomadation not more than 50 people where the travel distance is not exceeded"  
This is pretty much what I have. In fairness it is not a large occupancy. I would say that at most over the seven stories at maximum use 20-25 people. However it is still a floor at 20 metres about the ground, double to what is usually recommended. anyone have any similar scenarios?

[PhilB]

I agree Firemac, I think they are using the guide to suit their means. Part 6 does not restrict height of floors served by single stairs. Presumably because it was not envisioned that this type of situation would occur in places of assembly.

The clue is in the title to Part 6...Places of Assemby are usually designed for lots of people, therefore lots of stairs and exits.

Having said that you have to understand why the limit on building height is imposed on single stair buildings. Over a certain height the fire service cannot reach you with their ladders so you must provide an alternative means of escape in case your one stair is compromised.

These heights were set in the days of wheeled escapes and hook ladders...so probably only Kurnal and myself can remember that far back!!! How appropriate are those heights today??

The designers are stretching the boundaries...are they meeting the functional requirements of the building regulations?? does the lobby protection give adequate protection for the number of people on the upper floors??

[Firemac]

Thank you for your comments, I agree at the best of times the codes of practice which we deal with are contradictory, full of loopholes and not properly explained in cases.

 I don't think the use of lobbies is sufficient. A lot of the proposed lobbies are imposing on the design and in small rooms and stores in which i have them they will be just wedged open, (a lobby would have to be provided if it was just a signle stairs serving three story building) but as this is just a "paper exercise approval" its not really a valid agrument.

In regards the height, i have an idea of some of the basis on which these obsure notions were based (but realise i do not  know or understand them fully), the fact is in this situation the accomadation on any of the floors mentioned has no windows in any of these roooms to help aid rescue from the fire service.

[kurnal]

If it is multi storey with a floor at 20m wont it need a firefighting shaft in accordance with clause 29.2.2?

If it has a proper firefighting shaft (technically it needs a firefighting lift)  then personally I would not be  too concerned about a single staircase to serve the floors as described

[Tom Sutton]

In the sixties many blocks of flats where built in excess of 30 meters and a single staircase I also know of two similar office blocks, all built in accordance with CP3. I not aware of any serious situations involving MOE with these buildings which had, firefighters staircases, low occupancy levels and short travel distances. Should we be getting over concerned with the principle of single staircases in multi storey buildings providing the above applies?

[PhilB]

I don't think occupancy levels and travel distances have much relevance in the situation you describe TW.

So it's ok to place 50 at risk...but not 60 perhaps??? .........and you can reach your only escape within a few metres....oh bu**er it's smoke logged....but you didn't have to travel very far to get to it.

I know many flats have single stairs...but they also have alot of compartmentation. At the design stage why should we allow planners to disregard basic principles and cherry pick guidance to suit there needs.

Yes a single stair may be ok within a fire-fighting shaft...I would want to see some compensatory feature such as that or an engineered solution.

[Tom Sutton]

I must agree with you Phil however if Health & Safety applied ALARP I am sure they would consider these types of buildings to have a satisfactory MOE. I think it may be the Fire Service culture that will not accept the loss of one life other organisations apply a more clinical approach.