In existing properties converted into flats with a simultaneous evacuation strategy, is there ever a requirement to sub-divide the roof void/loft space?

For example, a four storey mid-terrace Victorian property converted into flats accessed via a single communal stairwell with two flats located at top floor level. 

An additional question is what is the requirement for fire separation between the roof void and the escape route/stairwell in a converted property with a simultaneous evacuation approach? (i.e. to stop a fire within the roof void passing into the escape route).

You have to achieve compartmentation between flats in accordance with HOUSING – FIRE SAFETY Guidance on fire safety provisions for certain types of existing housing and all situations will differ. Check out the above guide.

Thanks for your response Tom.  However, the LACoRS guide does not make any mention of roof voids/loft spaces as far as I can tell.