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FIRE SERVICE AND GENERAL FIRE SAFETY TOPICS => Fire Safety => Topic started by: Jon Barrett on February 22, 2008, 10:26:50 AM
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There seem to be difficulties in clearly understanding what are the requirements for sprinklers in residential for blocks over 30m as defined in the ADB.
This in my interpretation of how to satisfy the ADB requirements:
1. Does ADB allow resi sprinklers to be installed to 9251?
The ADB states that 'dwellings outside the scope of 9251' should be sprinklered to 12845.
But ADB also states that the 'limit on the scope of 9251 below 20m can be ignored' - so we DO fall within the scope of 9251 as defined in the ADB.
Therefore we can design to 9251
2. Do we need to provide full sprinkler coverage throughout the building?
The ADB states that ‘where a sprinkler system is specifically recommended within this document it should be provided throughout the building.
But ADB also states that ‘Sprinklers only need be provided in individual flats’.
Therefore corridors and common areas are unsprinklered.
3. Does the system need to comply with 12845 life safety requirements?
The ADB states that ‘any sprinkler system installed to satisfy the requirements of Part B should be regarded as a life safety system’.
Some people are reading this to mean that the life safety requirements of 12845 are to be applied.
BS 9251 states that ‘it covers systems installed for life safety purposes’.
Therefore BS9251 satisfies the requirements of the ADB.
Moving on to interpretation of 9251, for resi:
1. Flowswitches and audible alarms
For resi it states that... 'alarm arrangements should be in accordance with the authority having jurisdiction'
We should discuss and agree with the relevant authorities applicable to the project
2. Concealed and Recessed Sprinkler Heads
Is states that... 'Concealed and recessed sprinklers may be used with the approval of the authority having jurisdiction
We should discuss and agree with the relevant authorities applicable to the project
3. Pumped supply (for resi over 30m mains supply will be insufficient)
A single tank and single pump (no backup electrical supply required)
4. Pipework material
Plastic pipework can be used that complies with the relevant standards
Any comments and feedback on any of the above points would be appreciated.
Thanks,
Jon
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For 30m plus flats - Use BS 9251. Ignore the fact that 9251 is limited to 20m. Simple really - just read it with your brain turned on.
Dont see the point of fitting alarms to the sprinklers other than to warn you that its gone off by accident. (the flats will have smoke alarms)
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Dont have any experience of this at all so cant really help you in any meaningful way.
Presumably the 9251 sprinklers systems in individual flats will share a common water supply?
It would not be economic for each to have their own pumped supply and storage.
Would the block domestic supplies be pumped or by static head? Any circumstances/ subject to safeguards in which these may be used for a 9251 system- like using the feed from the public main is permitted where flow and pressure are sufficient?
If you go for common stored water and pumped supply what capacity would we look for? 30 minutes duration in one flat? How many fires in how many flats would we cater for in calculating storage? To what standards would we install any common pipework and what would be the basis for calculation of flow? Would we install ring mains and isolation valves?
Sorry to hijack your thread with a load more questions and sorry if these are banale- havn't had time to read up on 9251 for a long time.
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Its all in the standard - much easier than the BS EN for commercial buildings.
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Sprinklers are only recommended in the dwellings themselves. Hence the 'run-time' is 10 minutes (domestic, not residential sprinklers).
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30 minutes storage required by 9251 for residential. Only need to consider one fire. Max. of 4 heads discharging.
I'm aware of people pushing resi above 30m to be to 12845 OH1/OH2 protection. The ODPM review of the cost effectiveness of sprinklers was based on a 9251 level of protection - it reported that 'resi sprinklers are probably cost effective for resi over 11 storeys'. 12845 system would not be cost effective.
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Well spotted peanut - Most people havent spotted that one.
ADB only asks for a domestic system so 10 mins it is.
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I can't see reference to ADB ONLY asking for a domestic system - could you please quote the clause?
Thanks.
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I can see how it might be read that the requirement only needs 'domestic' protection...
- ADB says sprinklers 'only be provided within the individual flats'
- 'individual flats' are defined as 'domestic' under 3.7 in ADB (could also fall under 'residential' (3.17) in ADB as 'apartment's fall under this definition)
BUT...
'Domestic' application restricts the size of any individual rooms in the dwelling to 40m2
'Residential' application allows the size of individual rooms in the dwelling to be increased to 180m2
Hence the logic of increasing the storage capacity from 10 to 30 mins for water storage. Also, 'domestic' only requires a max of 2 heads, 'residential' requires a max of 4 heads.
If the apartment rooms don't exceed 40m2 then a 'domestic' system could be used otherwise you'll need a 'residential' system.
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I'd go along with that. 40m2 is a big room.
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Hmmmm...10 mins goes quickly when you are located on a floor 30m and above. And don't even think of relaxing any other (passive) standards because of the sprinkler protection!
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How do you envisage sourcing the water for these individual BS9251 systems in these tower blocks? Surely we are not looking at individual storage for each flat- and if we are not then the 10mins/ 30mins argument will become academic.
Again excuse me if I am out of touch- I havn't yet bought the BS and am still relying on the DD- Will buy it when I have a paying query!
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One supply and pump - 10 minutes worth of water in the tank for two heads.
Of course if you are trading off (design freedoms as thay call them these days) then I would definately up the spec.
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ADB clearly states that the systems are only required within individual flats, and that a BS 9251 (& in turn a DD 252) system is sufficient (note that ADB is thus recognising a DD as a design standard).
BS 9251 clearly states that systems within individual flats should be designed to a domestic standard.
10 minutes may not sound long, but it is 10 more minutes than a flat which less than 30 metres above ground, where the probability of fire is higher.
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So Wee B to be clear lets say we have a 25 storey block of flats wth 12 flats per floor and sprinklers over the 30m level, are you proposing 180 sets of pumping equipment and 180 1000 litre tanks or 1 pump set and one 1000 litre tank between the lot?
Myself I would gold plate the BS and go for something like two 10000 litre tanks and pump sets in the roof space of the block shared between the lot, so that we have resilience for maintenance, can cater for more than one flat having a fire on any day and due to the height to maintain the sprinklers for as long as it takes for the fire service to attend, to climb to the top floor and to get their equipment to work however long it takes. That way we would have continuity of attack on the fire.
But I am making it up as I go along- why doesnt it say something like that in the BS and the AD?
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1 pump set and one 1000 litre tank between the lot?
That's what it says
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The resilience and robustness of the system is proportional to the potential impact of a fire.
If a fire occurs in a clothing shop in a covered shopping centre then it is imperative that the sprinklers activate and contain the fire, otherwise hundreds of people could be injured/killed. Hence the requirement to meet the life safety requirements of 12845.
An apartment is fire compartmented from others around and perhaps there could be 6 people in an apartment - the failure of a sprinkler system has a much lower potential impact. Not much consolation for the people in the flat but that is how it works.
You also have to remember that the risk posed by a fire in an apartment is dependant on the type of fire (chip pan, christmas tree, cigarette etc), the time in occurs in the day (day/night) and the state of the occupants of the compartment (asleep, drunk etc.). Only a cetain percentage of fires will result in death.
For me a system designed to 9251 is appropriate for the potential impact. Remember ODPM's report found that for apartments over 30m sprinklers might be cost effective (emotive subject I know when you start putting a value on peoples lives). Sprinklers for apartments lower than 30m were not considered cost effective.
The ODPM report concluded that... 'The frequency of fire per accommodation unit increases with building height' - hence why they concluded that if sprinklers were installed in apartment buildings over 11 storeys then they might be cost effective.
It is a general rule of fire engineering that you only design for one fire.
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Confirmation received from LPCB is that the sprinkler contractor CAN'T issue a LPCB certificate for a installation to 9251 in a building over 20m because it is a 'major departure'.
Confirmation received from BRE (FPA) that the interpretation of ADB as identified in first post is correct.
However, as Wee Brian has already commented, they go on to say... 'You do need to be carful where people are proposing "design freedoms" or trade offs on the back of the sprinklers being installed. I would suggest that in such cases the specification of the sprinklers may need to be higher than BS 9251 provides'.
How much higher? This is where it becomes subjective and there is no clear guidance available.
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It is a general rule of fire engineering that you only design for one fire.
Yes but that general rule is applied per building- not per street.
Surely flats are considered to be totally seperate occupancies?
If you have 180 flats protected by a single minimal source of water you could have 179 flats with no protection at all for a considerable time following the single fire.
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A block of flats is a building and much smaller than a large shopping centre where the same rule is applied.
If you look at the incidence of fire you'll probably find you can cover a large area before buildings in the area would have coincidental fires (occuring independantly).
We looked at fire death stats for a 300 apartment block and according to the stats you would have one fire related death every 123 years.
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Kurnal, think about how often you have had a fire in your own street. I expect that the installer would fit a zone valve for each flat, or each floor in a big block so you wouldn't necessaritly loose protection to the whole block after one incident.
I think 9251 could do with a bit of tidying up now that its being used by regulators.
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I hope so too Wee Brian but am worried that someone may allow you to put in your small cistern to cover the lot because the rules dont specify otherwise.
Yes Jon but if the one fire in your shopping centre had the potential to put all the sprinklers out of commission there would be something very wrong with the installation. Especially if installed for life safety.
And the shopping centre has one centre management and one regime responsible for facilities management and repairs, whereas the flats may have 181 different persons responsible, 180 different installers fiddling with bits of the system some of which may be maintained, and 181 different insurance companies arguing with each other.
The ADB is a nightmare in this respect.
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The ADB has introduced the nightmare because they've referred to a domestic standard (diagrams are for houses only) and applied it to residential when the resi aspects of the standard haven't been sufficiently detailed.
This is where you get different people interpreting it differently.
The general industry conscensus seems to be a monitored valve and flowswitch on each apartment block floor serving a number of apartments. So there would be no parts requiring maintainence in the apartments. Complete installation in the apartments as the initial installation.
In respect of loss of sprinkler protection to the apartments if they were shut down for a period, it has to be remembered that (as long as there's no significant design freedoms) then sprinklers to apartments over 30m are really an enhancement and not an essential element such as fire compartmentation.
If design freedom, in terms of extended escape distances and reducing fire resistance, then yes are more robust system would be required I believe.
A 'small cistern' to cover the lot is what is currently being done because the standards don't ask for any more and as long as there are no significant design freedoms adopted then I think that's fine.
You don't have to have any storage, it could just be fed off the mains if there was enough pressure in them. Again it goes back to it being an enhancement rather than an essential element of the fire strategy.
9251 sprinkler installations with a 80% success rate (hopefully much higher) is better than them not being installed at all.
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The ODPM report concluded that... 'The frequency of fire per accommodation unit increases with building height' - hence why they concluded that if sprinklers were installed in apartment buildings over 11 storeys then they might be cost effective.
This conclusion was indeed in a nice yellow box, but there was no explanation of how the conclusion was reached. There are clearly more fires in higher buildings, but a quick glance at the graph above this conclusion shows that the number of fires in 8+ storey buildings is approximately double the number in 4 storey buildings. Not really suprising, as one would expect there to be twice as many flats in an 8 storey building as in a 4 storey building.
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Yup - but the cost of the sprinkler supply is shared out so it gets more cost effective.
Its also fair to say that things get a bit hairy in very tall buildings when tey are on fire so even if the numbers are a bit wayward the result is a sensible one.
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If anyone's still following this thread...
It was suggested earlier in this thread that 'domestic' standard could be used for flats over 30m rather than 'residential standard'. This was on the basis, as defined in BS9251, that as long as any individual room doesn't exceed 40m2 then the system only needs to be designed for the activation of 2 heads (rather than 4 heads if it was a residential application).
This is where the issue becomes a little grey...
A domestic occupancy is defined as an 'individual dwelling house, individul flats, maisonettes...'.
A residential occupancy is defined as an 'occupancy for multiple occupation not exceeding 20m in height... such as apartments'.
The definition of 'domestic' doesn't make reference to height, I think on the basis that it is for low-rise flats/maisonettes not those over 30m.
If you have a residential block that requires sprinklers because it is higher than 30m (as required by ADB) then I would suggest you should be applying the residential (i.e. for apartments) rather than the domestic specificaiton (i.e. design for 4 sprinklers not 2) as it falls more closely into that category.
Another issue that requires clear clarification by the authorities to avoid diverse views and debate!
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I still take the view that flats are domestic. Given that ADB tells you to ignore the 20m limit on scope.
I can see how you have come to a different conlclusion and iether of us could be right! perhaps the BS could be tydied up a bit to deal with this.
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Absolutely agree with that Jon. Keep bangin the drum!
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'You do need to be carful where people are proposing "design freedoms" or trade offs on the back of the sprinklers being installed. I would suggest that in such cases the specification of the sprinklers may need to be higher than BS 9251 provides'.
How much higher? This is where it becomes subjective and there is no clear guidance available.
Any "design freedoms" must be decided upon after full analysis of the effects of the compensating feature and of the effects of omitting whatever is being omitted. It's a balancing act and cannot be entered into lightly.
For example, there have been cases where recessed sprinkler heads have breached compartmentation in buildings. That is, the sprinkler system will operate for 10 or 30 minutes, but after that time it leaves a hole in what would otherwise be a line of fire resistance (the plasterboard ceiling). If the required level of fire resistance in the building is longer than 30 minutes (or 10 minutes!) then there is the potential for a breach. This is hardly what the designers anticipated and it illustrates how rigorous analysis is required.
It's also fair to say that things get a bit hairy in very tall buildings when they are on fire
The residential standard has to be the one for flats. The ten minute domestic standard is for houses where everyone is likely to be out in ten minutes (if they're going to get out). Flats are different. If you are comparing an individual flat to an individual house, then yes the same principle applies, everyone, if they are going to get out, should be out in ten minutes. But there is the added complication of the rest of the building. Ok, if the compartmentation is up to scratch then there should be no reason why anyone else should even find out about the fire, let alone evacuate, but maybe the compartmentation isn't always as good as we'd like to think it is. To come up with a particular solution for a particular building we're back to the balancing act.
perhaps the BS could be tidied up a bit to deal with this
There are many areas where the BS does not give complete answers, but application of sound reasoning when interpreting the principles being strived for should provide best solutions.
But ADB also states that ‘Sprinklers only need be provided in individual flats’.
Therefore corridors and common areas are unsprinklered.
What is the point of sprinklering an area where there will never be any fire load?
1. Flowswitches and audible alarms
For resi it states that... 'alarm arrangements should be in accordance with the authority having jurisdiction'
We should discuss and agree with the relevant authorities applicable to the project
The fire service may find it useful to have an indication outside a flat that the sprinklers are going off inside, but maybe it would be undesirable to raise the alarm for other residents. Maybe it would be desirable. It depends. So that's where the AHJ can have their say and tie the sprinkler arrangements in with the more general fire strategy for the building.
Stu
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Thanks for your comments Stu.
It's very helpful to flag up the issue of looking at what you're reducing when considering trade-offs.
Sprinklers have been introduced in ADB with no (or very little) trade-offs. Therefore I can see how people are looking to install the bare minimum because the requirement is an extra-over in some ways.
The ADB requirements have been introduced to protect life in the immediate vicinity of the fire, within the compartment.
As soon as you start looking at 'design freedoms' then you're in a different ball park and this is where your comments are extremely relevant - a common one is the extending of escape distances and eliminating fire rated enclosure of the entrance hallway in apartments - I guess though that even in that case it could be argues that 10 minutes (technically) would be adequate as they are reductions in the immediate vicinity of the fire and do not reduce down apartment to apartment separation. Although the resilience of the system needs to be considered - dual pumps and tanks etc.
However, I agree with you that resi standard SHOULD be applied to flats and I think that is what the BS is inferring.
The difference in domestic to resi standard is quite significant - 4 sprinks rather than 2 and 30 mins rather than 10 - that equates to a comparision of 820 litres to 5020 litres! Obviously the resi standard installation has a greater capacity to deal with a larger fire.
This difference can have quite a significant difference in installation cost - pipe sizes etc.
You stated that... 'There are many areas where the BS does not give complete answers, but application of sound reasoning when interpreting the principles being strived for should provide best solutions' - Unfortunately BS9251 falls woefully short of coming near the level of standard that is normally expected when we look at sprinkler installations (i.e. 5306:pt2). It is so open to interpretation, as this thread goes to prove.
Sprinklering corridors - this is a carry over from the LPC rules. Sprinkler contractors have suggested that this needs to be done to protect the sprinkler main (as is required by LPC rules). I agree with you, these are not required as the ADB states.
It just goes to prove how confusing the whole situation is when professional people can have views at opposite ends of the spectrum!
I'll be dropping a letter to the IFE Journal - be interesting to see the comments.
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The BS clearly defines individual flats as requiring domestic systems, not residential. How can this be interpreted otherwise?
The flat is treated as an individual dwelling and thus requires the same level of protection as a house. There is no impact on the remainder of the building to be considered. That is the difference between a domestic and residential system. Of course, if you have a hotel, care home etc.. then there is less significantly less compartmentation and thus the residential system is required.
Does any one think that BS 5839 needs amending to stop domestic smoke alarms being installed in flats? If the residential sprinkler argument is valid then it follows that only BS 5839 Part 1 systems are acceptable in flats.
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The BS clearly defines individual flats as requiring domestic systems, not residential. How can this be interpreted otherwise?
When is a 'flat' (listed as domestic) not an 'apartment' (listed as residential)?!
If the building is over 30m then I would suggest it's an apartment block and therefore should be designed to resi standard.
The resi definition makes reference to height whereas the domestic definition doesn't - again indicating that resi relates to tall buildings rather than low level blocks.
All very unclear.
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Does any one think that BS 5839 needs amending to stop domestic smoke alarms being installed in flats? If the residential sprinkler argument is valid then it follows that only BS 5839 Part 1 systems are acceptable in flats.
The ADB SPECIFICALLY states that 'flats' are to be provided with a detection and alarm system to 5839:part 6.
Unfortunately ADB fails to recognise that the designer has to make a choice between 'domestic' and 'resi' when referrring them to BS9251.
You can't equate terminology across different documents - just because ADB refers to resi over 30m as 'flats' doesn't mean that you only look to see what is required for 'flats' in 9251.
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ADB SPECIFICALLY states that sprinkler systems are only required within individual flats and can be installed to BS 9251.
BS 9251 SPECIFICALLY states that flats fall within the 'domestic' standard. If, for whatever reason, sprinklers were required in the common parts of a block of flats, or other apartment building such as an HMO, then the standard would be 'residential' in the common areas. This is all very clear in 9251.
Equating terminology across different documents is exactly what should be done, espcially when one document references another.
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9251 includes 'flats' in both categories - under domestic... 'individual flats', under residential... 'blocks of flats'
ADB clearly states (in 8.14)... 'BLOCKS OF FLATS with a floor more than 30m...' and 'sprinklers need only be provided within the INDIVIDUAL FLATS'
So I guess, in your interpretation, a 'block of flats' would include communal areas with rooms up to 140m2 but in the ADB's case you only have to sprinkler the 'individual flats' - and therefore only to domestic standard.
I can see where you're coming from but it's not exactly plainly obvious. It takes a lot of deciphering and can be read in other ways.
We certainly have extremes of views - considering this thread was started because a sprinkler contractor told us that on one of our projects we should be putting in sprinklers to BS EN 12845 and OH3!
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Jon,
I have to agree with your flexible attitude and desire to find the most appropriate solution depending on the circumstances.
Peanut,
A couple of things....
This is what 9251 says about residential or domestic occupancies:
"Residential occupancies, for multiple occupation, not exceeding 20 m in height, include apartments, residential homes, houses of multiple occupancy (HMOs), blocks of flats, boarding houses, aged persons homes, nursing homes, residential rehabilitation accommodation and dormitories.
"Domestic occupancies include individual dwelling houses, individual flats, maisonettes and transportable homes."
What can we say about this?
Well, first of all, the reference to the 20m limit should be disregarded completely. It is now commonly accepted that this limit is inappropriate.
Now look at where flats appear. Well, they appear in both descriptions (they don't make it easy, do they?). But look at the general descriptions under each heading. The residential occupancies are all larger buildings. The domestic occupancies are all small buildings/premises.
It's my belief, and that's all it is, that flats in blocks should have residential systems installed.
Next....
You use an analogy of fire alarm systems in blocks of flats, stating that part 6 systems are all that are required in individual flats. Well that's true provided that the compartmentation is good between individual flats and that a fire in any one flat will not affect the residents in any other flat. I might just agree with you that, if the compartmentation is good between flats, then all that is required is a domestic system in each flat.
What I would add, though, is that we would have to be absolutely sure about the compartmentation in the building to accept part 6 systems only or domestic standard sprinklers.
All in all, what is required in every case, as Jon has stated and restated, is a clear understanding of the needs of each particular building and a willingness to deal with a building in the manner that is most appropriate in the circumstances.
Stu
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Does anybody know why the threshold of 30m was chosen?
I recollect it was based on the BRE study commissioned by the ODPM on cost effectiveness of domestic and residential sprinklers but I think if we knew exactly who is at greater risk in apartment blocks higher than 30m and why at this height the risk increases and why it becomes necessary to enhance the passive measures with active measures then the issue would be clear.
Is the sprinkler to enhance the life safety of persons within an individual flat, or is it to protect others outside the flat involved by stopping a small fire in its early stages from becoming a bigger fire and thus ensuing that the passive measures- compartment walls, floors and doors are not tested towards their limits because the consequences of a fire at this level are much more serious?
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Like all trigger heights its a bit arbitrary. 30m is used throughout the AD as a definition of a "tall" building.
Things don't magicaly change at 30m but what else could you do?
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It would help if we know who or what the sprinklers are there to protect. Throughout the ADB, (although we are addressing life safety issues) its usually fairly clear whether a requirement is for the protection of general means of escape, specific parts of the means of escape ( internal layout of flats or users of mezzanines) , the elements of construction to make sure it stands up long enough to avoid risk, making sure that a fire cannot spread to affect too much of the building at any one time or to provide access and facilities for firefighters.
I struggle to see which element these sprinklers are intended to support. If its purely for the occupants of the flat involved domestics should do it. But why are high buildings any higher risk than medium rise buildings in this respect? If its for anything else then residential MAY be some help- greater chance of controlling the fire before the fire service arrive.
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I assumed we were talking about new build flats here, in which case we must assume that compartmentation will be good. If we cannot be sure of this then we would have to re-consider the way we deal with flats completely.
I am a bit confused about all this talk about a flat not being domestic if it is in a block. When is a flat not in a block? A flat on its own is a bungalow.
The BRE work looked at the incidence of fires in flats (blocks) of varying heights, and the upper height classification was 'over 11 storeys'. Since ADB already makes reference to 30 metres I guess it was decided to adopt 30 metres as opposed to 11 storeys as the threshold for sprinklers. The report also makes it clear that the sprinklers are intended to restrict fire growth within the flat. To me, but maybe not everyone, this means the sprinklers are provided to protect the occupants of the flat of origin. Afterall, there are very few instances of deaths on flats other than the one of origin.
Approving authorities should really look at the reasoning behind the new sprinkler 'requirement' before insisting on them in indiviual cases. Since the study looked at flats of over 11 storeys, perhaps there would be an argument for flats in a 10-storey, 31m high building not to be fitted with sprinklers. There is a nice comment in an article in the IFE journal (or whatever it is called now) about fire engineers using empirical calculations and calculating results to many decimal places. I agree with the point in the article, and would ask approving authorities not to be so 'exact' when insisting on limits placed in guidance documents.
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Sprinklers in these applications are there to protect the occupants within the compartment.
Once deviations away from the ADB are proposed - possibly extended distances and compartmentation rating reductions - then the 9251 requirements need to be reappraised to ensure the resilience and capacity of the sprinkler system is appropriate to compensate for any design freedoms.
Also, the application of domestic standard is probably fine for single height rooms less than 40m2 in size. But many apartments these days are being designed with mezzanines (i.e. a two storey space) and in this case I believe residential standard should be applied. You then end up designing the central system for 4 heads and 30 minutes anyway.
BS9251 mentions indivual flats and maisonettes under domestic - this could mean flats having their own entrances (not communal) - I used to live in a flat on a first floor that had its own entrance door at ground floor. Maisonettes would generally fall into the category of two story buildings.
This view would tally up with what Stu is saying in terms of the types of buildings being mentioned in 9251.
Taking this view, a building over 30m would fall into the 'block of flats' and hence 'residential' standard.
Although I think the logic of 'domestic' dealing with the apartments themselves and the 'residential' areas being for larger communal areas, such as communal lounges etc. makes sense.
The caveat to this is that all rooms in the flat should only be single height - if you have any mezzanines then I would suggest residential standard - as you could get more than 2 sprinklers activated due to the height of rise of the smoke from the lower level.