Protected Staircase 18 metre plus

[StuartH]

Both ADB and BS9999 state that all staircases serving a floor more than 18 metres high should be provided with lobby protection. I would be grateful if anyone can confirm the reason for this requirement ?

Many thanks.

[wee brian]

Lobbies reduce the potential for smoke to enter the stair.

The higher the building the greater the problems with escape and rescue.

So put lobbies in taller buildings.

The 18m is a loose link to the height at which external rescue would be possible. It doesnt really hang together that well anymore but 18m is still a reasonabl height at which to say a building is getting a bit tall.

[StuartH]

Thanks Wee Brian

I'm trying to ascertain the importance (and relevence) of the 18 metres as detailed within ADB and BS9999.

So you have the full picture, I have come across a 1960's office building which has a number of protected staircases, all serving a top floor some 30 metres above ground, however none of the staircases are lobby protected.

The cost of providing protecting lobbies retrospectively to the staircases is high (although I suspect they were orginally lobbied as some still remain), and although the requirement for staircases higher than 18 metres to be lobbied can be referenced (ADB and BS9999), the customer is asking for further explaination on the reason for the 18 metres.

My understanding was that it is to assist fire fighting, but was keen to see if any of you were aware of any additional reasons.

[Phoenix]

Stuart,

One of the most important reasons for the lobbies in these buildings is because it takes longer to evacuate tall buildings, especially if some of the people have mobility problems.  Even someone who you might not think of as disabled but with, for example, a slight knee injury or a dicky hip can take a long time to negotiate 18m, or 30m in your case, of stairs.  A single line of 30 minutes FR may not be enough.

You can come up with mitigating arrangements that reduce the need for lobbies on some stairs and at some levels but these arrangements have to be tailored for the precise circumstances of the building and such bespoke arrangements often fall foul of the passage of time so the best advice is to stick with the lobbies.

Stu

[CivvyFSO]

To address the relevance of 18m:

I believe that 18m = Approximate extent of usefulness of a wheeled escape.

Therefore above this, you are not being plucked out of a window by a normal 'wheeled escape bearing' appliance.

The 'actual' relevance if this is another matter entirely. This is not over-provision, but under-provision. ADB misses the no-mans land that exists between about 11m and 18m. Fire service ladders are now about 13m, so 10-11m vertical when braced against a wall. Until you reach 18m there are not the internal facilities for firefighters to use. BS9999 addresses this, as did BS5588. (One of the only things I like about BS9999)

[AnthonyB]

I've come across similar buildings, but if you dig deep enough you will find that in most cases they were lobbied and it's in the last few years that they have been removed in refurbishments that didn't go through building control (or the AI only considered the area being refurbished and not the impact across the building) or unauthorised works by tenants.

They have to be put back (assuming no engineered solution has been put in instead, which usually isn't the case) & it's just bad luck for the client.

It illustrates how important ongoing fire safety management is for a premises - with proper oversight these alterations would not have occurred and the issue would not have arisen.

A similar situation occurs with the splitting of floors on high rise buildings that for years were single occupancy but not realising the rule requiring access to both stairs, or adding new doors and access controls to historically split floors without realising that the other suites needed emergency access through them to the second stairwell & removing the original door furniture allowing this.

[Northern Uproar]

The 'actual' relevance if this is another matter entirely. This is not over-provision, but under-provision. ADB misses the no-mans land that exists between about 11m and 18m. Fire service ladders are now about 13m, so 10-11m vertical when braced against a wall. Until you reach 18m there are not the internal facilities for firefighters to use. BS9999 addresses this, as did BS5588. (One of the only things I like about BS9999)

It does cover it in a 'non direct sense' but asks for less than the BS - 11m is the limit for single stair buildings, and it assumes that only one stair will be lost, and 17.1 says that access requirements for buildings under 18m will be met by normal means of escape. 

[Phoenix]

Civvy and Northern Uproar,

I think you are muddling the requirements for means of escape and the requirements for access and facilities for fire fighters.  

All that nonsense about fire brigade ladders might be a consideration for providing access for firefighters to the upper floors of the building but for means of escape purposes no consideration should be contemplated about rescues via ladders.  I know you know this but I'm just stressing the point to make the distinction.

Therefore, the lobbies are required for means of escape purposes irrespective of the requirements for fire fighting access.  On that point though, you're right, fire fighter access should, of course, be provided by at least one of the staircases and this also requires lobbies (Not more lobbies! The same ones will do!)

I'm muddling myself now.

Stu

 

[CivvyFSO]

Stu

While I agree that FRS' do not tend to be plucking people out of windows, I do believe that the original source of the chosen limits was based loosely on post war building studies, which does state:

The main operational functions of the public fire service are:
1. To rescue persons who may be cut off by fire or otherwise prevented from using the normal escape routes. Rescue from buildings up to 42ft high to the topmost floor is regarded as a normal function of the public fire service, but as indicated in Part III rescue cannot be regarded as supplemental to structural means of escape above that height, though it would always be attempted.

While our present requirements would not contemplate window escapes at all in commercial buildings, the 42ft limit that PWBS always harped on about was a key figure for both MOE and FF Access, and this was explained as being due to the FS equipment available at that time.

[Tom Sutton]

The accepted teaching in the seventies including Moreton was,

I agree with Civvy and the FS equipment available at that time was the 50ft wheeled escape. It could only reach the windows on the fourth floor with addition height needed to effect a rescue. On decimalisation this became the 11m.

It was also considered that firemen could only be expected to carry the equipment required to fight a fire to the sixth floor after that a lift would be needed consequently the fireman's lift and a dry riser was required. As Kurnal said for the lift, all that was required was a protected electrical supply and a fireman's switch, there was other requirements but those were the most important. I believe some research was conducted on this matter. On decimalisation this became the 18m.

It was generally accepted that up to four floors a single staircase with double doors protection was acceptable above that multiple staircases with single door protection was acceptable to a height of ten floors. This was the height a TTL could effect a rescue above that we had to rely on the structural MoE and consequently a higher standard was required therefore all staircases had to be lobbied. On decimalisation this became the 30m.

[Phoenix]

..... above that multiple staircases with single door protection was acceptable to a height of ten floors. This was the height a TTL could effect a rescue above that we had to rely on the structural MoE and consequently a higher standard was required therefore all staircases had to be lobbied. On decimalisation this became the 30m.

Yeah, but, lobbies are recommended at 18m upwards.

Civvy,

I do not disagree with you about sources of figures.  And I think you would not disagree with me in acknowledging that the relevance of those sources is very limited in the new builds of today.  I'm not saying the figures are irrelevant, they are good(ish), but where they came from has little relevance. 

I feel we should be more interested in why we are sticking with these figures rather than reminiscing about wheeled escapes and TLs.  I think there is good reason for sticking with these figures...

Stu

[CivvyFSO]

The 'actual' relevance if this is another matter entirely.

Yes. I think we might actually agree in the main part Stu.

Toms example was really showing the reason for lobbies even when multiple staircases are present, which also traces its routes back to the days of TL's etc. It also makes more sense of the requirement for every floor to be a compartment floor in a building over 30m high.

So, to cut a long story short:

A single stair building at some point needs added protection to the stair.
History based this limit on fire service equipment available at the time and the ability of the fire service to perform rescues.
We have stuck with these figures, give or take a couple of feet/metres, because we still need a limit.

Just to add:
Even though we do have this no-mans land of external access between the 10/11m that the standard ladder can reach, and the 18m whereby we should have suitable facilities inside the building... Back when these figures were being played with the stairs will not have had the level of protection they are afforded now, i.e. Strips/seals etc, We can probably afford to have a bit more faith in the ability to get at the fire from inside the building.

[Tom Sutton]

Yeah, but, lobbies are recommended at 18m upwards.

stu

In the seventies 18m rule applied to high rise factories it was 24m for high rise offices and shops. (Blue guide) However I agree that this was then, not now and the relevance of those sources is very limited in the new builds of today. But have we answered StuartH question what is the relevance of the 18m?

[Stinky]

Check CP3 Offices guide, determine whether lobbies were recommended for your building.  If they were not recommended, maybe it is unreasonable to ask them to retrofit them? Maybe detection throughout compensates, check the old guidance to see what it says.  If they wereprovided but taken out in a refurbishment, then they shouldbe reinstated.  Look for evidence on the walls etc to determine this.

[Stinky]

I'm reading CP3 Part 3 for Office buildings. (1968).  Paragraph 2.1.5.2.2 asks for all single staricase office buildings to have a ventilated lobby between the accomodation and the staircase.  It also asks for lobbies to all stairs in multi-staircase office buildings over 18.3m in height.
Be good to ask if there was building control approval for the refurb and whether there was a fire strategy.