3 flats above shop

[massive1969]

Good old flats above shops saga...

Retail unit ground and basement.
3 storeys above each with 1 flat.
Height of highest floor of building <18m.

Building built circa 1850's.

Standard construction (Bricks, mortar, stone, slate, tiles, etc.)

60min separation between shop & flat.
60min separation between basement & ground floor shop.
Timber stair has been underdrawn.
Separation between each flat - uncertain at this stage...looks to me like timber tongue and groove floors but ceilings have been underdrawn with gyproc plasterboard.

AFD (Part 1) in shop which has been extended to stairway of flats at bottom and top of stair.
AFD (Part 6) Grade D in each flat (smoke) with heat detector in kitchen linked to building fire alarm system.

There is independent access to the flats which is a single stairway which is only means of escape. This discharges on to the street. Shop has its own independent entrance/exit.

Looking at guidance, which says...

Several flats over a shop (3+ storeys) - 30 minute fire doors to each flat door. 60 minutes between floors. Internal doors should also be fire resisting thus giving a 60 minute fire resistance between the flats and the staircase. Clear exit route out to a place of safety.

The design of the building is such that there is only one door leading to/from each flat i.e. not a lobby approach.

So, using this as guidance, should the flats each have a FD60s door as there is no internal door as such?? Including the top flat?? Or will FD30s suffice?

If it helps, they are immediately opposite a manned Fire Station!

[AnthonyB]

Looks like it's set up for full evacuate due to layout/structure and could also have been subject to Section 257 Additional licensing depending on where it is, certainly sounds like a LACORS guide type approach has been used.

One FD60S does not perform as well as two lobbied FD30S doors from a smoke control point of view. If you have full evacuate already you have to ask does it matter as much if you only have the single FD30S door from a point of view of the protection of relevant persons for Fire Safety Order purposes or not - will a fire affect the escape before alarm and evacuation (possible different ball game if considering the flats layout for HHSRS purposes). Is the common AFD in the flat just the kitchen heat detector and nothing in the vicinity of the front door? 

The problem with a lot of these set ups is they don't quite fit the guides, hence the need for individual risk assessment - I assume you've had an intrusive survey so you can be assured of the FR, it's a nightmare with these types to know the best approach if you aren't sure of the build and it's condition.

[GM]

What is the actual internal layout of each flat does it have an internal hallway with each room opening direct into this hallway?
If the flat directly above the shop has a floor level of max 4.5m above ground level could rely on escape windows? to this flat and you would hope that the flats above would have an internal protected corridor and a fd30 entrance door which would give the required protection? to allow others to escape but also  protect the occupants of the flat itself