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FIRE SERVICE AND GENERAL FIRE SAFETY TOPICS => Technical Advice => Topic started by: lyledunn on December 01, 2016, 09:17:14 PM
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I have a standard exposed grid 600x600 suspended ceiling below floor joists in a doctors surgery. The floor joists have no further protection and are exposed when you lift out a ceiling tile. They are 250x50 at 450mm centres with flooring grade chipboard over. The floor is really a roof space accessed via a trap door and loft ladders and is used for file storage. We have been asked to provide a staircase access. The only place to put the stairs results in travel distance being around 27m.
So this is a small single storey building and as I understand it we will need 60 min fire protection for the floor. The FRA has determined a current tolerable risk. L2 FA system in place.
We are not making the situation any worse than it currently is other than by perhaps increasing traffic flow to the floor by providing better access.
I can't see the ceiling grid providing the necessary 60 mins. Is there any way that this can be checked or can it be easily converted?
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Just for clarification is this in NI?
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Yes, does that matter very much Kurnal?
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It is only of relevance in respect of the technical guidance to be applied but not specifically related to tests on ceiling tiles.
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In England, that would be building work and you would need building control approval.
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Is there any manufacturers information? Are the tiles clipped in place or just resting in the grid?
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A standard grid-type suspended ceiling will provide no appreciable contribution to fire resistance and there is no way you could practicably upgrade it to provide 60 (or even 30) minutes fire resistance. If you really need 60 then a properly-specified ceiling would need to be installed (more likely you would remove it, fix an appropriate number of layers of plasterboard to the joists and re-install or replace - or make the new ceiling the finished surface).
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We do our best to meet the requirements of 9999 which in turn helps demonstrate compliance with building regulations. We have noted recently that BC often give way to mitigating factors rather than insist on strict adherence to approved guidance. Not sure if this is a good thing for simple buildings as it tends to lead to a degree of inconsistency which is not always helpful to project managers like ourselves. So for example, in this simple case, I am very confident that the appropriate requirements of neither 9999 or our Technical Booklet E are being met and would normally consider fire protecting the exposed joists. However, on previous jobs BC have allowed such a situation and allowed extended travel distance on the basis that a L2 system was installed. This is why I often turn to the expertease apparent on this forum, so I guess there is always an upside!
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Take a look at BRE Digest 208 for ways to upgrade from above, if you have L2, then what credibility does 60m have? why not 30m? but also speak to a structural engineer because you may be overloading the existing floor with all these files.
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Lyle you hit the nail on the head. A well considered and presented fire strategy document in cases such as the one you describe will often win the day and relaxations described within it accepted by the BCO or AI. This sort of work was my bread and butter before retirement. If however the inconsistency that inevitably arises is unhelpful then a fully code compliant solution is the reliable choice.
Remember the Building Regulations are solely to protect the H&S of persons in and around the building. Even an unprotected chipboard floor will offer some protection to occupiers, though not to firefighters. The old Building Regs 1976 gave some useful advice on this. Additional detection may well make up the difference to ensure occupiers are able to evacuate safely and accepted response times and travel speeds, e.g. As suggested in the SFPE manual or even BS9999 may help. But always consider also access for firefighting on the mezzanine and potential for rescue below it.
In respect of your initial query ADB 3 gives some practical guidance in respect of the use of suspended ceilings as a component of a compartment floor.
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Can you help me with interpretation of Table A3 in ADB3? If I am reading it right it seems to indicate that providing SOF characteristics are met, the existing suspended ceiling in my case, if deemed to be W, X, Y or Z can contribute to 60min fire protection?
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lyle
any pipes, wiring etc in the void?
If so, sparkies etc cannot be relied upon to re-clip the tiles.
Some excellent points listed!
davo
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That's true Davo. In fact there are ASDs throughout the void formed by the ceiling. There is also a number of building services items that would need access for inspection and maintenance. It would be a hell of a job to provide fire resistance from below. Perhaps it might be reasonable to suggest that the suspended ceiling will give some fire resistance to a floor that will be accessed by only one or two people on an infrequent basis and that the L2 system is at least some mitigation.
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Fire resisting suspended ceilings are a special system. Not in common use these days because of the maintenance issues.
You cant just plop different tiles in.
If it was me, I'd fix plasterboard or other system to the underside of the joists (in accordance with manufacturers spec). then put the false ceiling back again.
or you can blag you way out of having fire resistance but I don't think I'd be comfortable with that.
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You do need to know what you have got - one clue is that if the original tiles were not clipped in place then it is most unlikely to have been designed as a fire rated ceiling.
The other thing you might consider is whether the floor could be described as a raised storage area as described in B3?
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Can you help me with interpretation of Table A3 in ADB3? If I am reading it right it seems to indicate that providing SOF characteristics are met, the existing suspended ceiling in my case, if deemed to be W, X, Y or Z can contribute to 60min fire protection?
Sorry - wishful thinking, I'm afraid. Table A3 presupposes that the suspended ceiling has evidence of fire resistance performance that demonstrates it can contribute to the fire resistance of a floor (e.g. BS 476: Part 21), and places limitations on the situations where it can be applied (e.g. if the void above the ceiling were full of combustible stuff then it would be likely that its contribution might be compromised). It doesn't indicate that a ceiling that meets the conditions in the table will contribute to the fire resistance of a floor, to any defined level.
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Whilst I fully agree that where building works are carried out National Guidance should be followed the issue of proportionality must also be considered in my opinion. In this case it seems that a loft ladder is to be replaced by a staircase. If it is the case that the loft is still to be used for storage only, (we have not been told) then I cannot see why, in addition, the fire resistance of the floor needs to be improved. Lyle - please let us know.
In the scheme of things premises don't come much lower risk than a single storey doctors surgery.
One thing that has always bugged me is that with small low risk premises "applying the book " is often onerous and in my experience these premises are often dealt with a heavy hand by many enforcers when compared to much larger, higher risk premises or developments. That is where a comparative analysis can be useful.
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There will be no one on the first floor other than to retrieve a file. Even then, travel distances are mostly met. It is only from the most remote end of the floor where travel distance becomes an issue at around 30m. We have made the BC application. I will let you know how it goes. Regardless of what BC say, from a moral perspective, I need to be confident that I am not compromising fire safety unnecessarily.
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Its a little harder to make your escape/effect a rescue if the flames are coming through the floor or the floor has collapsed.
As somebody has suggested, you might be able to use the approach taken for storage platforms in AD B. but this will restrict the way the space is used etc etc.
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There will be no one on the first floor other than to retrieve a file. Even then, travel distances are mostly met. It is only from the most remote end of the floor where travel distance becomes an issue at around 30m. We have made the BC application. I will let you know how it goes. Regardless of what BC say, from a moral perspective, I need to be confident that I am not compromising fire safety unnecessarily.
At least you will have someonrpe to make the decision Lyle. It will depend on who looks at the submission.
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Well the builder went ahead with works on the strength of a site meeting with the BC officer and his boss. Project was quick to finish. All happy. Then comes the response from NIFire and Rescue which rejects the proposal simply on the grounds of TD (nearly 30 instead of 18). They are happy to review their decision but on chatting with officer he feels 30 has an intolerable feel to it, whatever that means.
Everyone on the new floor will move immediately on activation of the L2 FA so no pre movement time to consider. It took me and the practice manager 37seconds to reach the car park in front of the building at a quick but not hurried pace.
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Well the builder went ahead with works on the strength of a site meeting with the BC officer and his boss. Project was quick to finish. All happy. Then comes the response from NIFire and Rescue which rejects the proposal simply on the grounds of TD (nearly 30 instead of 18). They are happy to review their decision but on chatting with officer he feels 30 has an intolerable feel to it, whatever that means.
Everyone on the new floor will move immediately on activation of the L2 FA so no pre movement time to consider. It took me and the practice manager 37seconds to reach the car park in front of the building at a quick but not hurried pace.
The response being on paper following the BC submission? It would be normal for it to reject something which the book considers excessive. Your next move would be to request a site meeting with FR Service to discuss and to demonstrate that despite the TD you are still able to evacuate that area well within 2.5 minutes. The whole point of TD limitations is to ensure the recommended evacuation time but then this is benchmark stuff. The L2 will give immediate warning of fire to enable the evacuation to commence immediately. That is as good a measure than no alarm system with 18m TD.