Exploring the Implications: Protected Escape Route vs MEP Services in Light of Recent BS7671 Corrigendum

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:

  1. they are not essential fire safety or related and just passing through to serve other areas
  2. the cables feed general lighting and cleaners socket at this floor
  3. the cables feed general lighting and cleaners socket at floor below
  4. the cables feed access control at this floor
  5. the cables feed the access control floor below
  6. 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?