provision of FF shafts

[tmprojects]

opinions please.

A building with floor plan of 2,400M2 where all area's can be reached within 45m. and is fully sprinklered. would you accept just one Firefighting shaft?

BS9999 says;
in 21.2.2
sufficient number of shafts should be provided to meet maximum hose distances specified in 21.2.3. and at least two for building with floor area over 900m2

 21.2.3 says
you must be able to reach all areas within
a) if fitted with auto sprinklers then 60m
b) without is then 45m

To me; the fact you can acheive 21.2.3 with one firefighting shaft does not override the fact that 21.2.2 requires 2 or more because its over 900m2.

bearing in mind its not just a little over. i am of the (very opposed) opinion it does require 2.

Having said that, that was the code hugger in me. i am struggling to understand the logic behind a floor area over 900m2 requiring 2 even if you can acheive the 60/45 rule with one.

Have i missed something or is my initial judgement correct and 2 are required? If so why?

[kurnal]

Well I guess its to allow a pincer movement. You can drive a fire further into a building with a single pronged attack. Two shafts  may allow you either to use one to contain the fire into a corner depending on the geometry or surround the fire with a pincer movement if its in the middle.

[tmprojects]

would you say then that i am right in requiring 2

[Mr. P]

tm, I think you answered your own question. Remember, 9999 is a risk based approach. and, it is still a BS - not regs.

[wee brian]

You might find this interesting.
http://www.bre.co.uk/filelibrary/pdf/rpts/partb/Economic_impact_of_BDAG_proposals.pdf

[tmprojects]

I have been reliably informed that the rational behind the quantity of FF shafts is two fold.

1. sufficient in quantity and distribution to achieve the 45/60m rule

2. able to provide the brigade with sufficient resources to tackle any potential fire loading.

My question clearly falls within the 2nd statement. any floor space over 900m2 should be provided with 2 FF shafts to ensure sufficient fire fighting resources can be provided to deal with the potential fire loading.

So if I can satisfy myself, or be satisfied, that the fire loading within the building can be sufficiently tackled with the resources available from 1 FF shaft. and that the 45/60m rule is achieved, then one FF shaft is acceptable

[kurnal]

Do we know what constitutes "sufficient resources"?

Water supplies clearly come into it- the number of jets and volume of water that can be delivered from the rising mains. Numbers of staff? Directions of attack available to surround a fire? 

This is really important because so many designers are chipping away at the standards and often getting away with it.

 

[CivvyFSO]

tm, I think you answered your own question. Remember, 9999 is a risk based approach. and, it is still a BS - not regs.

Just to be a bit pedantic here, BS9999 has not linked the risk profiles to firefighting facilities. It actually causes many potential problems. (Think about a 90m travel distance in a building then see how that compares with the requirements for access for firefighters.)

TM, if you are a FRS bloke consulting under Building Regs and you are happy operationally that 1 shaft will perform the function, then there should be no problem. However, if you are a designer/engineer you would be much better off going to the FRS that this affects and discussing it with them.

[wee brian]

When 9999 was being drafted we did spot that the FF facilities might require more stairs than MoE. If you are taking a performance based apporach and the governing factor is FF f then it is what it is.

[tmprojects]

Do we know what constitutes "sufficient resources"?

Water supplies clearly come into it- the number of jets and volume of water that can be delivered from the rising mains. Numbers of staff? Directions of attack available to surround a fire? 

This is really important because so many designers are chipping away at the standards and often getting away with it.

 

i totally agree. the standards and guides are there for a reason. sure you can deviate, but it has to be justified. in this instance (now i know the rational behind 2 being recommended) the fact its sprinklered is the deciding factor for me. if designed correctly it should control the spread of fire sufficiently for one ff shaft being adequate to supply sufficient resources.

[wee brian]

But, if the standards writers thought that only one was adequate for a sprinklered building - they would have said so.

How do you justify you're - I know better than the committee - approach (Not necessarily disagreeing just asking what you say when questioned).

[CivvyFSO]

When 9999 was being drafted we did spot that the FF facilities might require more stairs than MoE. If you are taking a performance based apporach and the governing factor is FF f then it is what it is.

It is not just staircases, the whole principle of extending MOE based on the occupancy risk, provision of AFD etc, all gives extended penetration distances into the building. These distances are often justified for MOE, but none of the things that give rise to such distances helps a firefighter that has to enter the building.

A smoke logged building is still smoke logged regardless of the ceiling height. (Granted the temperature might be lower though)
A fire alarm that gives a clear benefit to the occupants does not help the firefighters.
A voice alarm does not help firefighters.
Whether people are familiar with the building also makes no difference to the firefighter.

So we are potentially creating buildings that firefighters are expected to penetrate much further into, despite the most recent version of ADB being adjusted in line with the findings from the BDAG research which suggested that about 34m is safe, decreasing in proportion to the number of floors climbed, but CLG compromised on the 45m from a fire main so as not to impact on UK PLC too much.

[wee brian]

Yes, that's the point I was making, just not so well.

[tmprojects]

But, if the standards writers thought that only one was adequate for a sprinklered building - they would have said so.

How do you justify you're - I know better than the committee - approach (Not necessarily disagreeing just asking what you say when questioned).

I totally appreciate your comment, why should i think i know better. In short i don't. hence my original question. i wished to understand the rational behind it.

if, as i have been advised, the reason for 2 is for potential fire loading. And 2 are needed to enable sufficient brigade resources to be committed. If it is demonstrated that the design of the sprinkler system will control the spread to a specified design sized fire. usually 9m2 with heat output of 1.5mw and with the inclusion of smoke control systems to each floor.  with my ops experience i can make a confident  judgement that resources from one bridgehead would be sufficient.

i know it departs from standards, but i whould be hard pushed to say it doesn't acheive the functional requirements

[kurnal]

TMProjects I think your proposal has a flaw. It depeds entirely on the management regime for the building to ensure that the fire loading is kept within the design parameters for the sprinkler system. In a poorly managed building it wont be,  and its the poorly managed buildings that have the fires.