Interconnected Rooms

[skwdenyer]

I hope you'll forgive a lay question. I've been attempting to digest the Building Regs and available fire safety documentation, but have reached a point of little / no clarification! I'm not attempting to get completely free consultancy here, just a pointer as to what assumptions I can make in examining a floor plan as a small feasibility study on a possible new (to us - in reality 100 year-old) office building.

I'm looking at a building which is rectangular and approximately 3500 sq ft. It opens out into free air at one short edge, and has no further walls through which exit could be made (all party walls). The building proportions are approximately 2:1 and it is a single-storey structure.

In the current plan, there are no formal corridors. There is "circulation space" front-to-back, approximately 30% of the width of the building, separated from the remainder by a masonry wall which should qualify as a compartment wall if necessary. The circulation space includes a cellular office (3 walls take a chunk out of the circulation space) and an open-plan "reception-style" sitting area. There is a clear "path" front-to-back in this space. This space opens onto the free air at the front. I'm treating this "circulation space" area as if it were a room (which I understand is how to treat a lobby), and the cellular office as an inner room (this one has only one exit).

The "2/3" space is divided into three rooms. The rear two have exits into the "circulation space", and open into each other. The front room opens onto the courtyard and into the next room "up" the plan.

I've done the calculations for exit distances from all parts of each room to the front exits (there are 3 exit doors there in total). There are 2 unique exits and 2 unique exit routes from each room / space, so the "2 or more exits" travel distances seem to apply. The angle between exits is sufficient. There are no protected corridors or stairwells (no stairs).

The "problem" is that one exit route from each location will always involve going through interconnecting rooms. With 2 exits these don't appear to be "inner rooms" within the meaning of Approved Document B.

The wording of that document is a little ambiguous, vis "A room from which the only escape route is through another room is called an inner room". The diagram (Diagram 17) shows a room with interconnecting (access) rooms on each of 2 exits and states this is not an inner room, yet an English reading of the sentence would seem to suggest that, even if a room had 10 exits, if all were through other rooms then the room in question would still be an inner room. Or in reality should this be read as "a room from which there is only one excape route, and where that escape route is through another room, is an inner room"?

As I said, I'm sorry to pick brains on such a specific question, but if anyone can offer any practical guidance on this I'd be most grateful. This problem affects the viability of leasing the building, without which it is pointless (and certainly beyond our financial means) getting a consultant in to do detailed work, and hence why I'm burning the midnight oil digesting regulations.

Here's a (not quite to scale) plan:

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     free air

[Bill J]

I think if you expand the quotation from Approved Document B you will find that the sentance reads

"2.4 A room whose only escape route is through
another room is termed an inner room and is at
risk if a fire starts in THAT other room (access room)."

The Capital Letters are mine, and not the document, it is therefore clear that an inner room has a single means of escape through one other room only, and it is the possibility of an undetected fire within that room which would prevent persons within the inner room from safely escaping, which is the concern.

If I read your drawing and notes correctly, and as long as the premises are occupied by a single occupier, (or managed to ensure co-operation) and that all doors are free from fastenings, so the alternative direction of escape is available at all times, I would be satisfied that there are no "Inner Rooms" present.

Of course I am always willing to be corrected.

Bill

[skwdenyer]

Bill

Many thanks. That's what I'd hoped was the interpretation!

"2.4 A room whose only escape route is through
another room is termed an inner room and is at
risk if a fire starts in THAT other room (access room)."

My copy of Document B says "the other room" rather than "that other room", which is why I was a little unsure, since "the other room" could apply to each access room when considered in turn. Your version using "that" is more prescriptive.

But again, thank you for the clarification, which of course does agree with Diagram 17! Yes, the building would be in single occupation and all doors would be free from fastenings and available at all times.