How many fire exits needed - Ground floor office

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How many fire exits needed - Ground floor office

Postby denzilW » Tue May 03, 2011 8:24 pm

hi, first post with general fire exit question.

i appreciate that this is difficult to visualise without picture but but i have a question regarding fire exits.

The building i work in is a low rise (ground floor only) rectangular modern building with one entry/exit at each end of the building, these are the the only 2 external doors in/out - each entry serves as final exit which leads into large open space car park at each end.

Basically a large bungalow with a door at each end!

The building has a central corridor (approx 25M) running from one door to the other with individual offices off the central corridor. Halfway down the corridor is a door marked "fire door" which is a substantial fire door that is always closed, but not locked.

Here's the issue - we wish to move in to one end of the building and lock the "middle" door with a view to leasing out the other half of the building to a new company - essentially then creating 2 buildings within one. Each end would have its own external door/exit and would essentially become a dead-end style building - the distance from the external door to the furthest office is not more than 12M.

No more than 12-15 people would work at each end of the building, the building is used for light office duties, has no machinery etc and otherwise is fire compliant.

Can you tell me, would it be legal to lock the internal fire door and thereby creating 2 separate offices, and what the reference for this is? My understanding is because the building is low risk, low rise with low population 1 final exit is sufficient?

Thanks

Denzil.
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Re: How many fire exits needed - Ground floor office

Postby Reddwarf » Wed May 04, 2011 9:03 am

I would go along with your findings on this because the single travel distance is less than 18 mtr's and the maximum number is well below 60 in each office. Does the office have a manual call point system or automatic fire detection?

How would you let the other office know that there is a fire in your side or visa versa. Also there would be a legal requirement to co-operate and co-ordinate, you would need to ensure the change is covered in your FRA. aslo the new company moving in would need to carry out their own FRA and communal areas would need a fire risk assessment carried out by the owner of the building if such a situation arises

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Re: How many fire exits needed - Ground floor office

Postby Keith1983 » Wed May 04, 2011 9:53 am

Why not let the other company use the corridor as a means of escape? After all you could have it closed and alarmed so that if anyone went through it an alarm would be activated therefor letting the everyone know it had been breahed. I presume at night the individual office doors are locked so should be no security issues and the alarm would stop people opening the door for fun. That way security is maintained and so is an alternative means of escape for both seperate companies.
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Re: How many fire exits needed - Ground floor office

Postby denzilW » Wed May 04, 2011 10:02 am

Thanks, very helpful.

regarding fire alarms, there are 2x maunal fire alarms at each end of the building that link into the same system.

Take your point about revising the FRAs.

Do you have the reference that refers to the 18M / 60 pax rule? I've only ever seen this referred to on various websites not the actual line or law.

Thanks again,

D.
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Re: How many fire exits needed - Ground floor office

Postby Reddwarf » Wed May 04, 2011 11:10 am

Keith1983 wrote:Why not let the other company use the corridor as a means of escape? After all you could have it closed and alarmed so that if anyone went through it an alarm would be activated therefor letting the everyone know it had been breahed. I presume at night the individual office doors are locked so should be no security issues and the alarm would stop people opening the door for fun. That way security is maintained and so is an alternative means of escape for both seperate companies.



if you can do what keith has suggested then it would do no harm but from a fire safety point of view it would not be required and could be simpler to assume the door is in fact a solid wall as the travel distance would still be acceptable. Also could be an issue that if one office is closed (locked up) and the other office tries to evacuate through the locked office they may not be able to escape from the building as the doors could be securely locked. Doors only need to be readily openable during hours of occupation.
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Re: How many fire exits needed - Ground floor office

Postby Reddwarf » Wed May 04, 2011 11:15 am

denzilW wrote:Thanks, very helpful.

regarding fire alarms, there are 2x maunal fire alarms at each end of the building that link into the same system.

Take your point about revising the FRAs.

Do you have the reference that refers to the 18M / 60 pax rule? I've only ever seen this referred to on various websites not the actual line or law.

Thanks again,

D.


there is no specific law on this but the HM goverment documents would bee seen as recommendation or good practice. it's free to download or £12 to buy

http://www.communities.gov.uk/publicati ... afetyrisk2


Travel distance are given on page 68 maximum 60 persons for one exit is on page 87. 60 people applies in my mind if you are talking of a room or ground floor with only one final exit. More than 60 people then a second exit would be required all other means to allow for more (fire alarm, sprinklers, additional fire compartment etc etc)

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Re: How many fire exits needed - Ground floor office

Postby denzilW » Wed May 04, 2011 5:04 pm

Again, really helpful thanks.

Ref the other guys coming through our corridor, this isn't an option as we double lock the exterior door with enhanced security and it is alarmed etc; the cost to convert would be very expensive.

thanks for the help guys. cleared this up nicely.
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Re: How many fire exits needed - Ground floor office

Postby Messy » Wed May 04, 2011 10:12 pm

You should have a look at ADB (approved document B) of the building regulations for further info. The standards in ADB apply during construction or alterations. If the aim is 2 x completely separate occupancies, the corridor should perhaps be made up with a 60 min stud wall. *(subject to the last paragraph below)

Means of escape wise, it doesn't sound problematic. Two points though:

1) If you have a manual fire alarm system and the panel is in demise 1, how are those in demise 2 going to access it to reset on those occasions when demise 1 is unoccupied? in addition, I don't think BS5839-1 (BS refers to fire alarm design) will allow one system covering two occupancies where those occupancies are completely separate. This might cause enforcement issues, but I haven't got my 5839 copy available to check.

2) Be careful about occupancies and purpose groups. ADB requires 1hr fire resistance between occupancies in some circumstances. A locked 20 minute or 30 minute fire door obviously will not achieve this


* If you are not using an architect or approved inspector, I would recommend a fire safety consultant be appointed to check over the proposals, as with the best will in the world, to give definitive advice blind and via the interweb is a bit of a lottery
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Re: How many fire exits needed - Ground floor office

Postby Jack Kane » Sat May 07, 2011 4:44 pm

Hey Denzil, welcome to the forums :D :wave:

Glad to have you with us.
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Re: How many fire exits needed - Ground floor office

Postby Alexis » Mon May 09, 2011 2:51 pm

Hi Denzil, welcome from me too. :wave:
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Re: How many fire exits needed - Ground floor office

Postby johnbone » Wed May 11, 2011 12:57 pm

Hi,
The answers are in Vol 2 of the Approved Document for Fire Safety in the Building Regualtions 2010.

In brief, if work-place (office, workshop, retail shop) has less than 18m travel distance (from all points where persons may be in the event of a fire) to a final exit, then ONE exit is acceptable. (If that exit door width is only 800-1000 wide then the limt would be under 60 persons.)

You will need to get a Building Regualtions approval for the proposed "Material Alteration" (i.e. the sub-division of the building into two units and the closing up of the alternative exit) to this building. Becasue without additional measures you may be making the future means-of-escape worse than it already is.
But, show any Building Control body, that you also have a suitable and sufficient fire alarm for both sub-units, and small enough max travel distances, and you should get a approval certificate in a flash!
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Re: How many fire exits needed - Ground floor office

Postby hammer1 » Thu May 12, 2011 1:24 pm

I do not think Building Regulations come into this issue as there is no new build or major physical alterations. It seems they are just splitting a ground floor office area into 2 with no alterations apart from locking a door. I might be wrong but I think building control may not get involved, worth giving them a ring though to confirm. Only say this as I have seen buildings change in this way with building control not bothering to get involved, however as with fire authority I find each building control officer has different views to the next one.

What you should be doing is reviewing your FRA (as you employ more than 5 persons it is recorded?).

Record the travel distance from the corner of your office to the final exit? Is it in line with guidance that allows a single escape route?

What are you occupancy levels ?

Is it open plan office?

What current, if any AFD system have you got? If it is only a ground floor building, then I would assume you have no AFD system in place

Have you extinguishers?

Liaise with new tenants on other side. request their FRA, ensure your fire emergency plan is communicated, share fire drills etc.

If fire door is to be secured, ensure all staff are made aware, any signs rmeoved.

With not knowing the full details, I would assume this would be ok so long as you conduct a FRA ensuring the above questions are answered.
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