Protected escape route vs MEP services
I wonder if you could share some of your expertise in the below
Last week on 25/05/2023, a Corrigendum to BS7671 was released by the IET applicable with immediate effect. (attached)
Here is a couple of relevant screenshots:
I have this newly built Insulated Concrete Formworks (ICF) four storey Office Building with a residential apartment at level 1, with its design and construction started in 2022
In the absence of the fire strategy document (which I requested), I would assume that the staircases highlighted by red rectangles would be classified as a staircase of a protected escape route.
Below I highlighted the emergency escape routes (red dotted arrows) and the main service runs (power, data, fire & mechanical) within a 610mm deep floor void. (green dotted line)
My concern is the lift lobby (see the exclamation mark); it is where all the MEP services pass through in the floor void.
If the lift lobby was classified as a firefighting lobby of a protected escape route – would the floor void be part of the firefighting lobby or excluded from it?
I am pondering it because of the services that are passing through and the 25mm casted penetrations through the slab for services below serving lighting, fire detection, and small power in the lobby below.
Reading the Approved Document B Volume 1 & 2 I assume the floor void forms part of the protected escape route, and in this case, the fire-resisting construction is carried out to full storey height – the walls are slab to slab, therefore any services penetrating the fire resisting construction must have appropriate barriers/seals.
I will risk the assumption that the raised floor should be class B-s3, d2 or better (Limited contribution to fire) and that most, if not all of the 600x600 raised floor types would comply with this requirement by default
My questions are: can I install cables in the lift lobby floor void if:
- they are not essential fire safety or related and just passing through to serve other areas
- the cables feed general lighting and cleaners socket at this floor
- the cables feed general lighting and cleaners socket at floor below
- the cables feed access control at this floor
- the cables feed the access control floor below
- can the wet system trench heaters be installed with electrical fans?
On another note, we see more projects where some corridors are being classified as a protected escape route as you know, the corridors are typically used as the primary service route at HL; therefore, the BS7671 corrigendum creates quite a challenge
What do you think?
Do you have any other comments?
Comments:
“Excellent question Jarek
As you will understand, I cannot answer the excellent question, but I am sure our A Team of experts will have a view. Paul McSoley, this sound like something you might have a view on?”-George
“Thanks George
This caused a lot of issues in the original 7671 amendment. The amendment has helped. Below is a heap of info that should help all on this one, sorry for the info dump! I also attach the fire terminology BS as well. - Paul McSoley
Hope this helps. Any views, just ping them over, it’s been a big debate.
The key question is. Does an apartment common corridor form a protected escape route? Also the original wording, see below, has been varied after many complaints.
The key with this, as George always says, is the space risk needs to be defined and agreed early what forms the firefighting parts of the protected escape route. We must also note what it states in the appendix 13.
Then, we also consider that the wording has changed to reflect what Part B and BS9999 already states. See below. The common corridor on the diagrams that Jarek sent are outside the firefighting shaft. We must also note that all cabling is generally B1/B2ca or Cca or lower, and im not sure on the secondary classes of S1 or D0 or A1.
Approved Document B (ADB) lists the following requirement within 17.9 paragraph 2:
Figure 1.1.1 – ADB 2019, Components of A Fire Fighting Shaft
Figure 1.1.2 – ADB 2019, Design and Construction of Firefighting Shafts
BS 9999:2017 lists a similar requirement to ADB below under 20.2.3 on page 112.
On Page 113 of BS 9999:2017 the following is also stated:
Jarek Wityk – “This is brilliant, thank you. I also had a conversation over the phone with Brian Kirby
Reading through all the guidance, I see two distinctive purposes:
- Safe evacuation in the event of Fire
- Escape Routes
- Protected Escape Routes
- Firefighting lobby
- Shaft or staircase of a protected escape route
- Protected lobby
- Protected corridor
- Protected stairway
- Safe access for Fire Fighters during the fire
- Firefighting shafts
These two purposes and guidance are merging: talking to Brian and reading Paul’s information,
I think it would be helpful if the BS 7671 Corrigendum were updated to clarify that It is possible to install ‘cables and other electrical equipment’ passing through ‘Protected Corridor’ as long as the services have fire-resistive properties for example, appropriate fixings, type of cable LSZH, 2h rated.
And what’s more important are to install with fire barrier which will create a compartment allowing safe evacuation and access for firefighters.
What I mean by that is - People misinterpret the risk, this is what Brian pointed out.
For example, if cables are installed at a high level in Protected Corridor, it is not sufficient to install a 2H fire-rated ceiling because the risk of combustion is above (risk=cables), and the ‘typical fire-rated plasterboard ceiling is tested for fire from below – not from above where all the metalwork and cables are (the risk). Therefore, such a fire barrier is pointless.
Brian suggested a so-called fire membrane that would protect the ceiling void, not allowing the fire to spread below the ceiling.
Reading the Building Regulations and BS9999, I think the stance with Fire Fighting Shaft is less problematic from the point of interpretation and practical installation.
The BS7671 Corrigendum threw spanner into the works because it makes it prohibitive to install passing services in the ‘protected corridor & protected lobby’ - because although the protected corridor is not the same as Fire Fighting Shaft,
However, it is its part of a Protected escape route - and this is how I read the BS7671 Corrigendum.
The BS7671 Corrigendum is the biggest problem because in most projects, the corridors are used as part of the service route – and without further guidance, consultants are unsure of what to do and then produce wrong solutions.
Now going to my specific project, I now have the Fire Strategy report and:
5.8 Staircases
5.8.1 Stair 1A (Serving All Office Floors)
In accordance with Section 3.3 of AD B: Vol2, the office building does not have a floor level greater than 11m, therefore a single protected staircase is acceptable. The protected staircase should:
- Be protected in 60-minute, fire-resisting construction, with FD30S self-closing fire doors.
- Be lobby protected on all levels, with the lobby including 60-minute fire-resisting construction, with FD30S self-closing doors. The lobbies should be kept sterile.
- Be constructed of materials achieving European Class A2-s3, d2, or better.
- Discharge directly to a final exit or passageway at ground floor level which leads directly to the outside. This discharge route should be free of combustible material, not have any rooms opening into it, and be at least as wide as the stair, with an outward opening final exit door.
- Meet the requirements of Approved Document K, and have:
- A minimum stair width between enclosing walls, strings or upstands of 1200mm.
- A minimum width between handrails of 1000mm.
- Not have access hatches for service risers open directly into the staircase, or staircase lobby.
It is noted that the lobby at L00 is technically not a sterile area as it will have a reception. This is considered acceptable provided the following is adhered to:
- The reception desk will be constructed of metal or hardwood.
- The computer will be a laptop rather than a desktop.
- No other office equipment (printer, TV, filing cabinet, etc) will be located in this lobby.
- Seating for visitors will be kept to a minimum and will be constructed of metal or hardwood. Electrical sockets will be kept to a minimum and should be located behind the reception desk to discourage visitors using them.
Approval Note 1: This is a design risk until approved by Building Control and the Fire Service.
5.8.2 Stair 1B (Serving L02 & L03 in the Office)
Stair 1B is an accommodation stair, and is not relied upon for means of escape. Therefore, this stair has no specific requirements in relation to fire safety.
Please see Section 5.5 for relevant information relating to Stair 1B.
5.8.3 Stair 2 (Serving Residential Unit)
Due to the emergency escape windows
[…]
5.15 Provision of Refuges
Refuges are relatively safe waiting areas for short periods of time. They are not areas where disabled people should be left alone indefinitely until rescued by the Fire Service, or until the fire is extinguished.
A refuge should be provided on all above ground levels within the protected lobbies of Stair 1A.
Each refuge should provide an area accessible to a wheelchair of at least 900mm by 1400mm. Where the wheelchair space is within an escape route, the wheelchair space should not obstruct the flow of persons escaping. Please see Figure 3 for an indicative depiction of a refuge space.
To facilitate the effective evacuation of people from refuges, an Emergency Voice Communication (EVC) system should be provided adjacent to each refuge. It is essential that the occupants of the refuge are able to alert building management that they are in need of assistance and for them to be reassured that this assistance will be forthcoming. The EVC system should conform to BS 5839-9 and consist of Type B outstations which communicate with a master station located at reception or adjacent to the fire alarm panel.
A management strategy will need to be developed for the evacuation of people with a disability and should incorporate details of how the building complies with the requirements of The Equality Act 2010. This should form part of the Fire Safety Management Plan.
To summarise
Reading the above, I understand that the lift lobby on each floor is treated as a ‘protected lobby’ the one at the Ground floor is recognised as not a sterile area however reception desk is allowed.
Therefore, I assume installing cables in the lift lobby floor void is allowed if they are not essential fire safety or related and are just passing through to serve other areas.
The cables shall be installed to minimise the fire and smoke spread risk. For example, 60min fire-resistant cables or cables in fire-resistant conduit or trunking and use fire-retardant cable terminations.
However
I am not so sure if it is allowed to install standard cables at level one floor void to supply lighting in the Ground Floor Lift lobby.
Can I install standard cables if the raised floor is rated 60min?
Can I pass through with standard cables if the raised floor is rated 60min?
Can I install standard cables if the raised floor is not rated 60min?
Why is the Fire Strategy allowing 60min not 120min?
What do you think? “
Roy Buckingham – “This is a great example of what we all should be doing in this industry. Collaborating to solve problems and having dialogue to ensure that works carried out to achieve one solution does not directly or indirectly reduce the effective fire safety integrity of the building.
Paul/Jarek this is great information, out of the scope of my usual field of application which is doors and hardware, but it is good to gain a wider understanding of these cabling issues as it has consequences for the application of access control into these areas which is within my remit.
I am regularly asked about the installation of access control and electric locking to the doors for protected escape stairways and I wonder how many security system installers are aware of the implications of wiring for access control to these protected locations, do they ensure that cables do not pass through the protected area? If they are not qualified electrical installers I wonder how much knowledge and understanding they will have with regard to BS 7671 wiring regulations and these requirements.
I await further replies to the additional questions and will save the email trail for future reference.”