Compartmentation of roof voids above self contained flats

[Suttonfire]

To add clarity, In the cases I am looking at there is no vertical compartmentation within the roof voids. It is difficult to retrospectively ascertain the FR of the ceilings in all cases, but all appear to be a minimum of 30 minutes fire rated. From my understanding of the Building Regs and the responses on this thread the fire rating of the ceilings does not negate the requirement for vertical compartmentaion (or adequate compensatory measure) in line with the fire rated walls from the floor below.

[wee brian]

you get my vote

[William 29]

Sorry, if I was confusing? Just to clarify then, 2 options as I see it:

1. No FR to flats ceilings but the flat walls (60mins) extended to true roof height, giving 60mins between flats and flats and common areas. This is as per the diagram in ADB and in an ideal world is the preferred option.

2. 30min or 60min FR to the ceilings but the flat walls do not extend to true roof height, but there are 30/60min cavity barriers (i.e. rock wool) in the roof void in line with the flat walls.

[wee brian]

Yes, but No 2 and the FR needs to go up and down - almost impossible to build - you have been warned.

[kurnal]

I have seen three solutions to this but retro installing a compartment barrier will always be a compromise and have several weaknesses in particular at the roof junction and at the head of the internal wall.
1- one local authority client installed plasterboard and stud partitions on the line of the internal walls within the roof void. They made a fair and durable job with access hatches using cut down fire door blanks, but this breached the fire door blank certification.expensive and messy.
2- a social housing provider installed rock wool FirePro mineral fibre cavity barriers again with cut down access hatches - fixing is critical at the head and base of the barrier, it is essential to follow the spec to the letter. The most appropriate and cost effective solution IMO if you are forced down this path.
3- another housing provider bodged it with smoke control curtain intended for subdividing cavities but ignoring the lack of integrity and insulation, the curtains were stapled together and within a year had been ripped asunder by other contractors. waste of time and money to achieve nothing.

[colin todd]

Wee B you are right as always but now that you can get B Regs approval from the world and his wife (in England and Wales, wherever the latter country is) you will find an A(dapatable) but Ignorant chap to approve it.  Equally, in an existing purpose built block of not too high risk, you have to be realistic, and a cavity barrier would be reasonably practicable.
I like local authority building control-I always used to liken them to a squelch in 2-way radio (breaker breaker Big Al 10:4 will understand).  It applied a bias current to that generated by the signal so filtering out the crap but letting good signals pass. 

[col10]

Another solution might be to upgrade the ceiling to be a compartment  floor, using the justification that if it was another flat above the then it would be acceptable for the flat accommodation to straddle the compartment wall.  
BRE Digest 208 gives guidance using mineral fibre fixed  with chicken wire between the joists  and tongued and grooved floor boarding.
There could be an electrical fire within the construction and there could be a fire within the void, but these things could happen if it were a flat above.
You would need to check any penetrations, eg seal all holes and fit intumescent collars to the  structure at soil pipe penetrations / pipes over 40mm dia.
The access hatch would need to be considered.

[wee brian]

Just remember that its the entire construction that gives you the fire resistance. Thats the ceiling, the joists (much bigger for floors that for ceilings) and the floor boards.

[Fishy]

Just remember that its the entire construction that gives you the fire resistance. Thats the ceiling, the joists (much bigger for floors that for ceilings) and the floor boards.

Ja - EI for ceilings, REI for floors (to BS EN 13501-2).

[col10]

Just remember that its the entire construction that gives you the fire resistance. Thats the ceiling, the joists (much bigger for floors that for ceilings) and the floor boards.

Ja - EI for ceilings, REI for floors (to BS EN 13501-2).

Ive amended my earlier comment as below:

"Another solution might be to upgrade the ceiling to be a [color=red]compartment[/color]  floor"

The compartment floor would have stability (R) , integrity (E) and insulation (I).  As wb pointed out above it is the whole floor that counts and exstg say "3 x 2",  ceiling joists on their own wont suffice, new joists could be fixed alongside.  The cavity above the mineral wool would need to be totally filled where it passes over compartment walls and around the perimeter.  Trussed rafters would make it more complicated.

[Suttonfire]

Hi All,

I would appreciate some views re the legal requirement for any works in relation to this topic. We have established that compartment walls above flats should be extended into communal loft voids, and that were this is not the case various compensatory actions need to be considered.

I have a client who has asked 'is it a legal requirement to take any action in the communal roof voids as the property complied to the building regs at the time it was built?'

Can anyone give me some more detailed views on the legal status of these types of recommendations, which require retrospective building upgrades.

I would also be interested to learn whether it has ever been allowable under previous Building Regulations for compartment walls separating flats from eachother/the common areas not to be extended into the roof void.

Thanks

PS... Here is my take on the legal basis of the requirement to implement measures in the roof void, based on current guidance:

The law, The Regulatory Reform (Fire Safety) Order 2005 (RRFSO) sets general fire safety objectives to be achieved. For example it is a requirement of the RRFSO to ?reduce risk of the spread of fire on the premises?.

Accordingly, a Fire Officer could take enforcement action if he/she determines that by not installing compartments within the lofts the Landlord/Managing Agent has not taken reasonable steps to ?reduce risk of the spread of fire on the premises?.

Whilst the existing layout of the lofts may have considered to be adequate at the time of construction, it may not be considered to be adequate now (due to developments in technologies, and the understanding of how fires can affect buildings etc).

It is accepted that it is not realistic/risk proportionate to update existing buildings to meet all current approved guidance; however, the guidance should be used to establish just how far removed the original standards are from what is considered acceptable today, and whether this has given rise to an unacceptable level of risk.

[Dinnertime Dave]

Just reading through this thread again, my scenario is slightly different in as much as the building is a supported living scheme so residents are more vulnerable. I have ruled out the over boarding option as it does not adequately deal with a roof fire or a fire spreading from a flat window through the soffit, the practicalities of carrying out the work and the additional weight applied to the structure.

My preferred option is controlling the fire loading and the installation of cavity barriers. But do I need to do all flats, every other flat or even every third flat? Could I extend the size with the addition of detection? 

[Jim Scott]

I would always be inclined to provide, at the very least, cavity barriers at each compartment line if I couldn't provide full compartmentation.

I have seen this go wrong a few times, where the idea of a fire-resisting ceiling has been provided in lieu of vertical compartmentation.

Although it softens the blow, I do think that detection is inadequate mitigation in this scenario.  Particularly as the likely intention is stay put.

[Suttonfire]

Just to pick this up again.

Would you consider that any form of retrospective cavity barrier is required if the floor within an open communal roof void is a concrete slab?

Obviously there is potential for fire spread across the open void but little chance of ingress into the flats.

[John59]

Can't envisage an issue with that and I'm sure the risk assessor would record the the matter accordingly after examining it. Problems tend to arise where the Fire Authority have been informed that the compartmentation will be taken up to rafter level at consultation stage.. and then find the premises has not been built to plan. But I can't imagine any objection being raised to this provided adequate fire stopping and intumescent materials are used where necessary.

There's a reluctance to accept horizontal protection in place of vertical fire barriers which is understandable. Systems are now available in which ceilings and floors can be upgraded to provide an hours FR from above and below and meet BS 476;pt 21 criteria. Whether the relevant stautory authorities will accept these or not seems to be on a case by case basis.