MoE from a Historic Monument

[GB]

I have a 5 storey historic monument with a spiral staircase of minimum width of 750mm. Each storey has a single room leading directly to the stair with an open door to allow members of the public access with a single final exit at ground level direct to fresh air.
Evacuation is simultaneous with no members of staff at the upper levels - only sounders throughout. The current occupancy that the site uses is 150 people over the 4 storeys and they would like to increase to 200. Using ADB Volume 2 I would suggest that the occupancy capacity should only be 60 - I am interpreting this correctly? The monument can not increase stair width. I have identified some further control measures that they require but still am questioning the capacity. Is there any further benchmark standards for historic / listed buildings with public access?

[nearlythere]

Do the rooms contain combustibles?
Are they furnished in some sort of fashion?
I would also look at this from a safety angle with the spiral stairway and so many persons. Some historical buildings with steep spiral staircases I have been in do not have landings and someone falling over at the top would not stop until they reach the bottom probably taking others out on the way down.

[CivvyFSO]

There isn't always the answer that people want to hear. Taking quite a strict view, you say there is no way to increase the width... Then I agree with that and blame that as the reason you can not increase the occupancy. Obviously a more accurate assessment of the risk is needed, but it is quite possible that if done correctly, a risk assessment might just as easily say that the occupancy of 150 should be reduced. People who get consultants in for this type of job expect them to risk assess the problems away and somehow make the building safer with a few 'excuses'.

It is my opinion that L1/L2 doesn't compensate for a poor escape routes in this circumstance.

[kurnal]

1- What is the building used for? Are the 150 persons visitors, sleeping or working?
2-Are there any combustible materials or ignition sources?
3-What are the doors to rooms like from a fire point of view?
4-How long would it take to get people out in an emergency?
5- Is there a role for fire suppression systems in the rooms leading onto the staircase? 

I agree with all the above postings but it is very important to protect our heritage buildings by keeping them in use if possible.

[Phoenix]

GB,

ADB generally recommends 60 per floor for a single staircase - but not for a spiral 750mm staircase with open doors over 5 storeys.  ADB is not designed to deal with such buildings.  It says,

"...adherence to the guidance in this document might prove unduly restrictive.  In such cases it would be appropriate to take into account a range of fire safety features, some of which are dealt with in this document and some of which are not addressed in any detail and to set these against an assessment of the hazard and risk peculiar to the particular case."

This supports the replies so far.

As kurnal and ADB allude to, some leeway might be in order in such cases.  But only if justifiable.  Five storeys is a long dead end and a spiral staircase is a difficult route.  150 sounds like a lot of people to put in such a situation.

Possible solutions might be along the lines of L3 detection (or better) and fire doors on magnets to the stairs or ever present staff trained to shut doors on the alarm. Alternatively, these buildings often have a pretty low fire loading and it might be acceptable to do without fire doors if it can be all but guaranteed that there will never be a fire that affects the escape route.  That might be a tall order.

150 people makes it sound like an unusually popular hertitage building.  Often, these buildings have a very low population (e.g. 8 ) for 99% of the time and only have large numbers (such as 150 or 200, as proposed here) when they have special functions or exhibitions.  If this is the case here, then you can consider having two fire safety strategies - one for when the building has a population of 8 and one for when the popular functions are on and a heavy staff presence is required.  That doesn't mean that you can chuck out the fire safety rules when just 8 are there - I might be one of those 8!

Stu


 

[Mike Buckley]

I think we need more information about the building. Some of the questions have been asked above, but some of the other questions are:

What is the construction of the building and the staircase? A stone building with a stone staircase and stone floors is a different case to a timber framed place with softwood floors.

Who are the people in the building and what are they doing? Disipilined employees working are a different to a stag/hen party.

How often will the place have all 150 people in it?

Can a fixed firefighting system be introduced such as a water fog system?

I agree that 150 sounds a lot but unless there is a great deal more information available the answer has to be a fairly definite maybe.

[GB]

many thanks for input thus far.

The figure of 150 people is for around 10 weeks in the year with the occupancy dropping to around 10 / 20 during the winter months. The visitors are not all english speaking and are a range of mobility levels.

The building fabric is stone with combustibles within each room although limited.

From the top to the bottom in an unrestricted stair i.e not full of slower people in front of me takes around 2/3 minutes.

At present only staff members on the ground floor entrance - limited CCTV on the upper levels.

The doors could be upgraded to some extent with smoke seals and automatic closers without losing any heritage - although the approval process would take considerable time!

[kurnal]

GB
Using risk assessment you will no doubt evaluate the current use of the building and make decisions on the necessary measures to manage the risk. If designing the building from scratch in the 21st Century we would not do it that way but we are where we are and there are clearly a lot of people who want to visit the site.

It would not be acceptable to society to shut it down or make major changes so we have to reflect this in the way we use and manage the fire risk. Take a look at many similar buildings- castles and cathedrals - and take a leaf out of their book ( ie i mean better ones who have thought about what they are doing). But dont think about increasing numbers till you have fully justified the current position. 150 persons may be too many.

[CivvyFSO]

Possible solutions might be along the lines of L3 detection (or better) and fire doors on magnets to the stairs or ever present staff trained to shut doors on the alarm.

I would say that L3 detection would be a minimum anyway since we could have unoccupied floors below unsuspecting people looking around above, so it wouldn't be compensatory in my opinion. I would also say that we need the doors shut to reduce the risk, not held open.

Compensatory features here would be a voice alarm, or trained staff on every floor, and lobbies or a pressurised stair.

For me you need to ensure that the stair remains free of smoke enough to let everyone down it in safety. It is a tall order.

I have my jack boots on today just in case you haven't guessed. (And they are nipping a bit)

[wee brian]

Sometimes in this kind of situation we have to look at reducing the risk of fire. An "intrinsicly safe" approach to any materials in the building perhaps? Non combustible or treat everything in sight with flame retardents. Use high spec electrics etc.

It may be that max population should be driven by other issues. If its a pokey tower then theres the problem of the punters getting in each others way and knocking each other down the stairs.