Fire Stopping of Electrical Risers

[ponch]

Hi all,

This is probably a basic question which I should know but is something which I have recently been confused about due to a number of premises I have recently visited.

My question is should electrical risers be fire stopped at each level within a building so there is no free run of smoke / flame between the compartment floors? 

Until recently it was my understanding that electrical risers should be adeqautely fire stopped at each compartment level.  However, recently I have visited a number of multi-storey residential premises where this has not been the case.  All have adeqaute FD30s fire doors leading from the risers into the common areas and the shaft itself appears to have been constructed with appropriate fire resistant materials.  I know this may be a straightforward question and I understand that Approved Document B diagram 31 does not show that a protected shaft requires fire stopping at each level but I just wanted to check with your expert opinion.

Also, I if may note that from the risers there were vents leading from the riser into the common area.  I can only think there are vents within the risers leading into the common area because of the gas supply within, which inline with ADB require venting.  However, due to the electrics within these risers surely the vents would compromise the required compartmentation of the shaft. 

This was not picked up in previous risk assessments, by the building control officer of by the local fire service during their recent visit so I am wondering if it is just me missing something glaringly obvious.

If anyone could help me with this it would be much apprecaited

[kurnal]

A protected shaft in which the elemnets of structure are to the same standard of fire resistance as the compartment floors they penetrate, and the doors half of that standard does not need sealing at each floor level- if you did it would not be a shaft.

However a shaft with vents into each storey is not a protected shaft and either needs the vents sealing or an alternive solution found.

[nearlythere]

The point of the shaft is because of the difficulty with fire stopping around services. If you could easily fire stop services between floors there would be no need for a shaft. 

[Phoenix]

The vents are such an obvious breach of the fire resistance that you start to look for reasons why they might have been accepted.  Could I ask if you have checked to see if they contain intumescent dampers.  The presence of these, though not ideal, might make the vents comply with the requirements for fire resistance.

Stu

[wee brian]

not all floors are compartment floors. most aren't.

[ponch]

Hi there

Thank you all for your replies.  The vents I mentioned don't appear to be of the intumescent type and there are a number of fire stopping issues within the shaft itself where services have not been suitably fire stopped once it penetrates the wall.   

I should have also pointed out that there are automatic smoke vents within the protected lobby areas in which the shaft/vents leads into.  So I can only think that with the automatic openable window system, which should be interfaced with the alarm (although at present this interface has not been established), smoke from the shaft would pass into the protected areas activate the alarm due to the AFD in the protected area, which then opens the windows to allow for venting of smoke coming from the shaft.

However, although this may have been deemed acceptable by the Local Fire Officer and Building Control in the case of the vents from the shaft to the protected areas with AFD there are also vents in some protected lobby ceiling areas directly outside apartments which are not provided with automatic smoke vents.


Thank you again for any help you can give
 

[kurnal]

So can we confirm this is a block of flats, the riser is soley within the staircase at all levels, the only openings into the riser are into the staircase and there are no unsealed openings into any other part of the building apart from the staircase.

If this is the case then is the riser simply part of the staircase itself? The only question that would then remain is whether, in accordance with ADB, the risk within the riser warranted protection and fire separation. In a single staircase building the electricity meter cupboard should for example be enclosed by fire resisting construction. If the riser communicates with the meter cupboard it should either be fire stopped where the riser leaves the cupboard enclosure or the cables would then need to run within a fully protected shaft. The ADB does not make specific comment about gas meter cupboards but simply refers to the relevant installation regulations and codes of  practice. If the two services share the same shaft there would probably be some conflict. Is there a common meter cupboard for gas and electrics?

[ponch]

Yes they are block of flats.  But the riser is not in the stairwell but is in the protected apartment entrance lobbies which are accessed directly from the staircase.  The access for the risers is within the apartment entrance lobbies and currently a number of the risers have vents from within the riser and above the access door to the riser itself

there are seperate gas and electric meter cupboards for each apartment block but the gas piping is in the same riser as the electrics.

[kurnal]

Then it is clearly non compliant as the lobbies are all linked vertically by the vented riser. Duct needs sealing at each compartment floor level. Rockwool firepro or similar.

[ponch]

Hi Kunal

Thanks for the advice.  It was as I suspected but I just couldn't understand why it wa never picked up by building control, the fire officer and the previous risk assessor so i thought i was missing somehting.

Thanks again for your help

[wee brian]

If I've understood correctly, it does sound a bit iffy.

[Speyside]

Then it is clearly non compliant as the lobbies are all linked vertically by the vented riser. Duct needs sealing at each compartment floor level. Rockwool firepro or similar.

Yep Kurnal just stuff in some Rockwool, or what about some plaster board and some fire retardant foam. Get it done properly, to provide a fire resistant separation to the same level as the compartment. With a material that has test evidence or certification to support its application for that purpose. Passive protection has some excellent guidence documents and the ASFP website will point you in the right direction.

[kurnal]

Thats a bit prickly Speyside?
Rockwool is the name of a recognised leader in the passive field and Firepro is their range of fire stopping systems.
I did not say stuff up the holes with a bit of gunge did I?

[Speyside]

Thats a bit prickly Speyside?
Rockwool is the name of a recognised leader in the passive field and Firepro is their range of fire stopping systems.
I did not say stuff up the holes with a bit of gunge did I?

Not intended as such sorry. My point being that its the bit you don't say that counts and particularly as there are many many products produced by Rockwool and indeed in the Firepro range and the vast majority of all these will not be suitable for the situation described. I see it all the time with risk assessors, they mention a product or resolution method without stating what has to be achieved at the end and what should be done/checked to ensure the resolution makes good the initial problem.

[kurnal]

Thanks Speyside I was being over sensitive and touchy. I was going to amend my posting but you beat me to it.

The fact is they need sealing to an appropriate standard, one would expect and hope to see this carried out to the same standard of fire resistance as the compartment floor.

But there could be circumstances where the assessor may take some account of the fire protection offered by the existing (flawed) riser protection and it may be legitimate to consider whether the principle risk to relevant persons in this case is the spread of fire or the passage of smoke. Only the assessor can judge. Only he has seen it. But whatever,  your point is valid and well made.