FireNet Community
FIRE SERVICE AND GENERAL FIRE SAFETY TOPICS => Fire Safety => Topic started by: tmprojects on January 21, 2011, 12:05:34 AM
-
opinions please.
22 storey building. 2 stairscases. both with FF coms, FF lift and dry riser.
1960's prefab build. One is lobbied. One staircase is not lobbied.
to achieve the required occupancy (ESPECIALLY WITH THE HOT DESKING) you cannot discount a stair. so you need both in any calcs.
one staircase is fine. the other has rooms with one hour fire doors leadING directly onto the staircase. these rooms have various occupancy (store, Office, maintenance, meeting, etc).
management is very disjointed so cannot be relied upon.
-
Currently, they must discount the un-lobbied staircase (but that will lead to some serious problems mentioned below). If the unlobbied staircase is un-useable due to smoke or fire spreading into it then everyone will have to use the single available (lobbied) staircase. This will put a lot of people into the staircase and the main concern at this stage is that, due to the number of people already in the staircase, the people on the fire floor may not be able to enter the staircase quickly enough to escape the effects of fire. The fact that it is 22 storeys makes it no worse than if it was only a few storeys, probably slightly better in fact because we should be confident that the floors are compartment floors.
Is it phased or simultaneous evacuation? What I'm talking about in the above paragraph relates to simultaneous but if there is phased evacuation and the fire floor evacuates on its own in the first phase then the main concern mentioned above is dealt with. There won't be people from other floors clogging up the stairs stopping people leaving the fire floor.
But that's only part of it and the rest isn't good. There's very little resiliance in only having one lobby-protected staircase to this height. How long will it take everyone to leave the building using a single staircase? How long will it take the disabled people to get down and out after everyone else has evacuated? And here's the really bad thing. Which staircase are the fire fighters going to use to access the fire floor? The one not affected by fire, I would suggest. Will everyone be out by the time the fire fighters start attacking the fire, holding the doors open with their hose? I doubt it.
ADB says this, "4.27 In tall buildings over 30m in height, where phased evacuation is adopted, there is a potential that persons attempting to escape could be impeded by firefighters entering and operating within the building. This potential varies with the height of the building and with the number of escape stairs that are available. Generally, this can be addressed by incorporating special management procedures into the evacuation strategy in consultation with Fire and Rescue Service. However, in some very tall buildings,
typically those over 45m in height, physical measures may need to be incorporated into the building (e.g. by discounting a stair or by some other suitable means)."
So you may have to discount the one remaining staircase as well as the one affected by fire. That doesn't leave many staircases left for use by the people still inside the building when the fire fighters arrive. And don't blame the fire fighters - their alternative is to let it burn.
This building has serious problems that should be dealt with immediately. They've got away with it for years but as from now both staircases should be lobbied.
Stu
-
Thats a cracking response Phoenix. Answer complete.
The scenario sounds a little like an exam or interview question to me though?
-
Just to add: If you go down the phased evac route you really need lobbies anyway. I suppose you could aim for phased just down the one dependable stair, but like Stu says, that will be the preferable stair for firefighters, which will cause further problems
to achieve the required occupancy (ESPECIALLY WITH THE HOT DESKING) you cannot discount a stair. so you need both in any calcs.
That being the case, you only have two options:
Lobby the stair.
Pressurise the stair.
-
Pressurise the stair.
Good point. A very viable alternative. If there are many small rooms opening into the stairs then the lobbies may not be viable.
But pressurisation is not an easy route either. Both stairs may need to be pressurised, a number of AOVs will be required on every floor, existing ductwork may need additional automatic dampers, new ductwork, much disruption during installation and very long commissioning, a huge amount of work for an existing building, thinking about it I'd go back to the lobbies if possible!
The scenario sounds a little like an exam or interview question to me though?
kurnal has a point there. The existance of such a building seems unlikely in today's fire safety climate. Maybe abroad somewhere? Or as kurnal suggests, on an exam or interviewer's question paper?
Stu?
?
-
I've not seen an existing build that high that bad in the UK - but I have seen very close examples, high rise and low rise that have critical issues but 'got away' with it.
Nothing to add to the replies above, I certainly wouldn't put my name to justifying it as is.
-
Thats a cracking response Phoenix. Answer complete.
The scenario sounds a little like an exam or interview question to me though?
I can see why you would think that. but this is a genuine question.
Also, i never said this was a real building! I mean, how could this possibly be? That would mean the building was off the inspection radar and the occupiers could of changed its layout in this fasion without requiring permission. that couldn't happen... Could it?
So. this is a purely hypothetical question.
I should however. clarify something in my question. Both staircases are lobbied in a sense. BUT one stair has rooms directly off it. making it, in some respects, unlobbied. but not completely.
-
can i throw something else in the mix.
now i know its not about money. but lets say you where gonna stump up the bill for this. what would be your recommendation? what would you put your name to on the FRA? (for fairness i try to consider this).
you cannot lobby. the layout doesn't allow it.
The rooms off the stair have 1Hr fire doors. (clearly someone's attempt to bodge the job) (in this hypothetical building).
The Building has an L2 fire alarm.
Possible solutions:
stop using the rooms and lock them off. this would solve the problem at no cost.
restrict their use. if so to what. (i.e would a chair store be ok?)
lobby the rooms that can be lobbied. lock off the others.
presurisation.
please criticise them all. i know i can.
what would you do?
-
Tear it down.
Stu
p.s. I wanted to say that all along.
-
Sell it to some other unfortunate property owner!
It wouldn't be the first time, particularly as most building fabric surveys don't look at fire safety in any detail and the new owner normally has the FRA done after they've signed on the dotted line.
It can be a nightmare finding an acceptable risk specific solution and normally the client ends up having to spend 10's of thousands, void whole floors from use or just planning permission for a new development & knock it down and sell on the land.
Oh and some that do nothing, fingers firmly crossed behind their backs.
If I can find a cost affordable solution by tailoring actions to the specific situation (rather than guide hug) I will, but if none exists I will plainly point it out to them and that's it, I wouldn't compromise my report just because the solutions cost too much.