If the floor level of the inner room is greater than 4.5m above ground level (as with the top floor of a typical three storey house for example) the use of an egress window may not be safe and therefore an alternative solution will need to be sought. This may well be one that does not create an inner room situation in the first place.
Some walls around stairways (typically in houses 3 storeys or more in height) need to have fire resistance to ensure a fire in one of the rooms off of the stairway doesn’t unduly affect the means of escape from other rooms in the house. In other houses (such as in two storey houses) the walls may not need to have any particular fire resistance, but would still afford some protection to the stairway by containing the fire and smoke for a period of time.
The impact of the removal of an internal wall on fire safety should be carefully considered. In two storey houses, the removal of such a wall could normally be compensated by the provision of mains powered interlinked smoke alarms and egress windows from the other rooms off the stair. However, in houses of three storeys and greater this compensation may not be sufficient. The exact features needed will vary on a case by case basis.
A new wall (including any door leading through it), which separates a room from the stairway may need to have adequate fire resistance (typically in three storey houses) and, in the case of a door, be self closing.