BS5839-6:2004 Large Houses

[JPAH]

Can anyone explain the reasoning (if there is any!) behind the recommended upgrade in alarm system from Grade D to Grade B when a 2 storey dwelling has a floor area that exceeds 200m2?

The possible reasons I can think of are:
1. there is a higher potential of the house being multi-tenanted - not single family.
2. long runs of wiring and more smoke alarms may cause the system to be unreliable (I'm no electrician!!)
3. ?? potentially longer travel distances for occupants - ie therefore detection and alarm needs to be more reliable to give warning (basing this assumption on the old max 30m travel distance recommendation in some guidance)

I ask the above question in relation to not upgrading the system in a new house.  The only mitigating features I can think of would be to introduce 30 minute sub-compartmentation with fire doors (where it wouldn't normally be required) so that no area exceeds 200m2 OR introduce enhanced means of escape - say over-provision of doors/windows OR if the layout lends itself to particularly short travel distances.

Any comments much appreciated.   

[nearlythere]

Can anyone explain the reasoning (if there is any!) behind the recommended upgrade in alarm system from Grade D to Grade B when a 2 storey dwelling has a floor area that exceeds 200m2?

The possible reasons I can think of are:
1. there is a higher potential of the house being multi-tenanted - not single family.
2. long runs of wiring and more smoke alarms may cause the system to be unreliable (I'm no electrician!!)
3. ?? potentially longer travel distances for occupants - ie therefore detection and alarm needs to be more reliable to give warning (basing this assumption on the old max 30m travel distance recommendation in some guidance)

I ask the above question in relation to not upgrading the system in a new house.  The only mitigating features I can think of would be to introduce 30 minute sub-compartmentation with fire doors (where it wouldn't normally be required) so that no area exceeds 200m2 OR introduce enhanced means of escape - say over-provision of doors/windows OR if the layout lends itself to particularly short travel distances.

Any comments much appreciated.   

I take it you are having a problem with Building Control?

[JPAH]

No, just have been asked advice on the issue recently (and many times before!) and it is one that I have never understood.  Never been able to get a common sense answer.

[nearlythere]

No, just have been asked advice on the issue recently (and many times before!) and it is one that I have never understood.  Never been able to get a common sense answer.

This is one of those little facts of life without good reason JPAH other than it is in Building Regs and BS5839, the latter considering a 200M2+ house a country mansion. No proper reason given other than "justified and considered appropriate" Don't know who justified or considered it appropriate.
Don't think LACORS goes for it.
Maybe you are looking at it from the wrong end. Maybe a BS5839 Pt1 system is the norm with downgrading to a less sophisticated system being appropriate for the more humble abodes.

[JPAH]

Thanks - you are probably right.  Just wondered if I had missed something obvious.  Causes no end of problems for Building Control this one.

[nearlythere]

Thanks - you are probably right.  Just wondered if I had missed something obvious.  Causes no end of problems for Building Control this one.

True.
Had to help someone who did not realise that the detection system required for his 200M2+ country pile was more than the single point detectors and this was after it was built. Went for wireless which was more expensive but less disruptive for his french pine floors and freshly skimmed walls.

[JPAH]

My scenario is similar to yours above.  It was missed and they have already installed a simple compliant 'domestic' system.  I thought good mitigation might be sub-compartmentation which is inplace already via fire doors (although not required under bregs).  The building has a large ground floor and tiny first floor.  Escape is available from every room (via a door in the majority of cases) directly to the outside. 

I understand that BControl want to let it go but are just looking for someone to say it is ok because......?  I think it is ok because of the above features.  I cant think of any other possible compensation for the 'non-compliance'.

[nearlythere]

My scenario is similar to yours above.  It was missed and they have already installed a simple compliant 'domestic' system.  I thought good mitigation might be sub-compartmentation which is inplace already via fire doors (although not required under bregs).  The building has a large ground floor and tiny first floor.  Escape is available from every room (via a door in the majority of cases) directly to the outside. 

I understand that BControl want to let it go but are just looking for someone to say it is ok because......?  I think it is ok because of the above features.  I cant think of any other possible compensation for the 'non-compliance'.

This is one of those situations where unless you know why the Pt1 system is "justified or considered appropriate" it is difficult to make judgement on compensatory features. I think the bum protection approach is that the owner must acknowledge and accept that the system is not strictly as is required by BC. He/she probably won't care anyway.