Vertical Dead End or Unprotected Staircase?

[Tadees]

Hi All,

I don't believe the guides are totally clear on a scenario where initial travel on a floor and down some stairs should be treated as an initial dead end or whether this should be treated as an unprotected staircase where, if overall travel distance is met, there is no issue of providing FR or AFD to the rooms @ the base of the staircase which open on to the staircase. See example below:

Question

On a 2nd floor of an existing building, we have two small offices. The staircase from the 2nd floor is open to the first floor. Once you get down the stairs on to the first floor, there are 3 small offices open to the staircase i.e. no FR (normal doors & glazing to the 3 offices). Once we reach the base of the staircase at first floor level (the initial one way travel distance being approximately 14m) there is 2 ways out, i.e. at first floor level there are 2 separate staircases (one to the left & one to the right). The nearest available final exit can be reached within 45 metres.

Do the 3 offices on the first floor need to be FR or have AFD in them because of the initial 14m of travel from the 2nd floor & down the stairs being one way travel?

Or do you say that you can have an unprotected staircase because overall travel distance can be met?

[kurnal]

Are either of the staircases serving the first floor enclosed or separated from each other and the ground floor  by fire resisting construction?

[Tadees]

The staircases are separated from each other by FR. One fire cannot compromise both.

[kurnal]

To be fair Tadees it sounds pretty ropey to me.

Where you feel a situation is not adequately covered by the FSO guidance it is reasonable to have regard to other guidance such as ADB for benchmarks as to what an acceptable standard might be. The ADB would give clear guidance on acceptable standards for a small building with 3 floors. BS5588 part 11 / BS9999 likewise. I don't think you can simply apply the travel distance guidance in the vertical plane - convection becomes involved too.  Its not much help to someone on the second floor to get early warning of a fire on the ground floor if when they open their office door the landing is thick with smoke.  Ok  there may be other factors such as the way the builing is used that can be used to create an argument on equivalence. Sorry if this is garbled and smacks of sucking eggs.

[Tadees]

This is actually a common occurrence in all occupancy types. TD from upper floors to final exit can be met yet normal risk rooms open on to the staircase. In a normal dead end we would put FR & AFD in, yet the guides allow such a 'vertical dead end' where TD can be met. Ridiculous really?

[Phoenix]

It may not be a great layout but ADB will allow it if certain conditions are met.  See 4.32.

Smoke detection is required at first floor level (plus possibly elsewhere).