Lobby protection to a staircase

[Bill G]

Can you please assist -

I have recieved a BR consultation for a 8 storey office building which has two staircases ( one a FF stair) . It is proposed that the second one is protected by means of a single door.

They have argued that as the width of the FF stair is sufficcient to take all of the occupants that the lobby protection to the second staircase can be omited. I can' get my head around this- they are claiming that this is an engineered solution ! Am I loosing the plot !

The stairs in question are at either end of a rectangular floorplan ( which is open plan)

[kurnal]

Sounds like they are confused over the rules on discounting a stair when calculating the necessary width/ exit capacity . Lobbies or protected corridor approach is required for all stairs in a building of this height. I suggest you take a look at BS5588 part 11 chapter 9 which is set out in a more logical way than the ADB, in my opinion.

[CivvyFSO]

Bill

The second stair may indeed be capable of taking all the persons in the building, but the simple fact remains that persons who are in the building WILL (and should) use both stairs to evacuate.

It looks to me like simple cost-cutting trying to hide behind an 'engineering' tag. Possibly in the hope that you will be scared of challenging the 'engineering' behind it.

[nearlythere]

Bill

The second stair may indeed be capable of taking all the persons in the building, but the simple fact remains that persons who are in the building WILL (and should) use both stairs to evacuate.

It looks to me like simple cost-cutting trying to hide behind an 'engineering' tag. Possibly in the hope that you will be scared of challenging the 'engineering' behind it.

Civvy. Surely they will only use the one stairway if the other is unusable. In a situation like this where more than one stairway is needed, when one stairway is discounted due to fire the remaining, be it one or more, must be capable of taking the occupancy factor.

[Midland Retty]

Yes because of the height of the building surely needs lobby / corridor approach onto the staircases.

UNLESS... the BCO is saying that as both staircases can take the maximum number of occupants only one needs to be protected as he is working on the logic that you will only have one fire.

That is to say therefore if one is lost to fire you can turn your back and you have an alternative... you can stop travel distance in protected routes.

And travel distances only applies to the nearest exit.

Furthermore in theory you should never loose a protected route to fire in the time needed to evacuate. (you could loose access to the storey exit onto the protected route but you do have an alternative).

But there are fundemental problems with that strategy.

I can sort of see where he is coming from if that is the case. But that is on the strict proviso of AFD being installed.

AFD plus one line of FR has been accepted in the past as constiuting a protected route but I have to say this particular scenario doesn't sit easy with me.

The idea of corridor approach / lobby is to prevent smoke entering the protected route.

[PhilB]

AFD plus one line of FR has been accepted in the past as constiuting a protected route but I have to say this particular scenario doesn't sit easy with me.

The idea of corridor approach / lobby is to prevent smoke entering the protected route.

Retty single doors onto a staircase provides a protected route....regardless of AFD. In this situation due to building height the stairs need the additional protection of a protected lobby or a protected corridor.

I think you are confusing this with the old home office guides, when you mention 1 door and AFD, but  the old blue guide still recognised that in tall buildings additional protection was needed.

The theory behind it is we cant reach you by ladder so you need to make sure your stairs work.

[Bill G]

Many thanks so far to those who have responded.

We have now replied to the AI along the lines that if they go ahead with it that upon completion the building may be subject to immediate enforcement action.

[wee brian]

Sounds OK to me - if I discount the stair without a lobby then the other stair does the job.

I dont have to discount the lobbied stair.

[PhilB]

Sounds OK to me - if I discount the stair without a lobby then the other stair does the job.

I dont have to discount the lobbied stair.

And what happens to the person on the eighth floor who choses to use the weak stair and is 10 minutes into his journey when the stair becomes smoke logged???

You're that blokey who wrote the new Animal Guide aren't you!

[nearlythere]

Wee Brian
In this case the lobby protection is not a compensatory feature to enable one to relax the number of stairways required for escape purposes. Lobby protection is the minimum standard for each stairway.

[wee brian]

How does the fire know what the lobby is for - you guys crack me up.

[PhilB]

How does the fire know what the lobby is for - you guys crack me up.

mmm great point Wee Brian!!!

The fire doesn't know what the lobby is for or where it is going to start.

Spookily enough, neither does the blokey on the top floor who always uses the stair without lobbys to go to work.

He will leave using the weak stair and lets say the fire starts on the ground floor adjacent to that stair with the single door protecting it.

So 10-15 minutes after ignition the smoke and heat break into his stairway while he perhaps is at the second floor....what does he do now???

[CivvyFSO]

Civvy. Surely they will only use the one stairway if the other is unusable. In a situation like this where more than one stairway is needed, when one stairway is discounted due to fire the remaining, be it one or more, must be capable of taking the occupancy factor.

I think that you missed my point. In a fire what will happen is neither staircase will become unusable immediately other than on the fire floor, where they are likely to lose one exit depending on the location of the fire. You are then left with 6 other floors who still have access to both staircases, and they will use them.

Then you are faced with people coming down from the 7th storey, passing a fire that is only one fire door away as opposed to 2 doors away down the ff stair. And this is in a building that probably requires no compartmentation between floors, so to end up having to track back across the building to the ff stair could be "not ideal". Or 'pants', to quote the technican term.

[wee brian]

I've just read the original question - if its 8 stories then the stair should be lobbied regardless of the discounting rules (always read the question - Never my strongpoint - failed a lot of exams that way).  Para 4.34 in B1 is clear enough.

Ignore my earlier comments - much as it pains me to say it Phil B is right. But the Horsey guide was nothing to do with me!

[nearlythere]

Civvy. Surely they will only use the one stairway if the other is unusable. In a situation like this where more than one stairway is needed, when one stairway is discounted due to fire the remaining, be it one or more, must be capable of taking the occupancy factor.

I think that you missed my point. In a fire what will happen is neither staircase will become unusable immediately other than on the fire floor, where they are likely to lose one exit depending on the location of the fire. You are then left with 6 other floors who still have access to both staircases, and they will use them.

Then you are faced with people coming down from the 7th storey, passing a fire that is only one fire door away as opposed to 2 doors away down the ff stair. And this is in a building that probably requires no compartmentation between floors, so to end up having to track back across the building to the ff stair could be "not ideal". Or 'pants', to quote the technican term.

Can't quite see where you are going here Civvy. The principle in this type of building, or part thereof, is that one has to design the MOE to take into consideration the loss of one stairway, where a multi stairway condition is required. The additional smoke protection of the stairway by the provision of a 1/2 hrfr lobby is the norm. It cannot be assumed that any of the stairways are made fire proof.
Do I pick up from your comments that you think the FF stairs is the only escape route and therefore no need to provide the proper level of protection to the others?