?AFD in lieu of fire resisting lobbies - single staircase?

[Underground]

I have often heard that it is acceptable to have AFD in lieu of fire resisting lobbies on a single staircase but:

1) what can you have - does there need to be AFD on the staircase as well as in the rooms off the stair? I am thinking of offices here - not sleeping risks.
2) Are there any written down official guidelines for this one?

Many thanks in advance.

[PhilB]

AFD in lieu of lobbys is from old home office blue, lilac guides etc. Those guides gave option of single fire door and AFD throughout floor instead of two fire doors in single stair conditions. AFD in stair way only is a bit pointless...you need to be aware of fire before smoke enters protected stairs.

[Ken Taylor]

I think he's asking about AFD on the stair in addition to throughout the floor, Phil, rather than instead of.

[kurnal]

Dont overlook the fact that the Approved document B in some cases allows a single stair without lobbies up to 5 floors. I think the old FP act guides looked for lobbies if you went to three storeys and above.

It would be most unusual not to put detection in a stair if putting it in offices off the stair- it goes against the old philosophy of systems building up in coverage- M, L3, L2, L1.
It may not be wrong to do it- if the detection is purely in specific areas in lieu of lobby protection you could perhaps through a risk assessment justify it as an L5 system. For what it would save on the cost of the installation though- probably one or maybe 2 detectors I reckon it isnt worth it. Probably cost more thinking about the weasel words to put in the risk assessment and variation to BS5839

[PhilB]

I think he's asking about AFD on the stair in addition to throughout the floor, Phil, rather than instead of.

Quite so Ken, I must read the question!!!  Sorry Underground.

[Underground]

Many thanks - so an old 18th century traditional built buliding with no lobbies and 4 floors could well be covered with full smoke detection rather than having to install lobbies - if I have read it right?

Kurnal - not sure what your "weasel words" line was about - can you explain please?

[PhilB]

Yes, but make sure your doors and partitions are in good condition, doors should be self closing and fitted with intumescents strips and smoke seals.

[PhilB]

Many thanks - so an old 18th century traditional built buliding with no lobbies and 4 floors could well be covered with full smoke detection rather than having to install lobbies - if I have read it right?

Kurnal - not sure what your "weasel words" line was about - can you explain please?

It would probably cost more to pay a consultant to justify why you haven't got detection in the stair enclosure than it would to provide it.

Is that an accurate translation Kurnal?

[kurnal]

precisely phil

[Underground]

Thank you one and all - I will therefore look at smoke detection on each landing as well as inside the door, with SC's 30 mins and smoke seals/intumescent strips to ensure I secure a good single means of escape for all 4 floors.

[Ken Taylor]

We did this with a Grade 1 listed. Stairs and floors going off in all directions - but AFD everywhere.

[saddlers]

Kurnal,
ADB allows single stairs up to 11m but lobbies have to be provided on all single stairs with more than 1 floor above or below ground level.

[PhilB]

I would recommend reading both the new ADB and the old version and then reconsider your last post Saddlers. Contradicting Kurnal!!! are you mad!!

[kurnal]

Phil thanks for your confidence but in truth the old Kurnal can talk out of his backside from time to time and never minds being told so.  
We are all shaped  and limited by the range and depth of our past  experience, and discussion can help broaden our knowledge.  

In this case I was referring to paras 4.6 and 4.34a of the new ADB.
Thats making some big asumptions on the size of the building and travel distances of course because  I should have stressed that these paras do only relate to small buildings.

We could also of course refer to BS 5588 part 11 sections 9.6 and 10.2.4 though these have never been as clear in their application as is  set out as the new ADB. The problem with the 5588 explanation is that the dispensation with the lobby protection for small buildings only appears in the commentary section 9.6.1 and not the recommendations in 9.6.2 .

For heritage buildings there is another potential problem that will need to be managed- if we have a single staircase we will need to keep it a sterile environment - and this can be difficult to achieve as they usually have loads of nooks and crannies crying out for an armchair or sofa.

[PhilB]

Yes discussion is good. At first glance it would appear ADB requires lobbies on single stairs with more than one floor above first or below ground floor.

Both old and new ADBs except small buildings from this requirement.