We are currently refurbing a single story building which has 3 corridors approximately 35m in length running in parallel between the final exits.  We are installing FD30S doors as approximately the midpoint of each corridor.  The issue is that at the midpoint is another corridor that connects the three corridors but is not connected to a final exit (basically |-|-|) we can either put a door at the midpoint of each (2 doors) or at the end (3 doors).  Does anyone have any suggestions or an alternative, currently the walls are not full height and so require fire stopping.

What is the fire doors being install for, and a sketch would easier to understand than your description also what guidance is the premises subject to.

Building is a large store,  the doors are cross corridor doors.  The building is to under go an internal refurb.

 

In my opinion two FD30s doors at the intersection of the west and cross corridor also similar arrangement for the east corridor. Also three FD30s doors at the intersection of the central and cross corridor, would achieve acceptable travel distances to places of relative safety/ultimate safety. What I am unable to establish if it is possible for a fire to pass from any  section of corridor to another via the office space/sales area.