We live (and are co-freeholders) of a 2 storey Victorian building that comprises 2 flats; one upstairs and one downstairs, with a small communal hallway at ground level (1x3m) which contains both flat entrance doors. The building was converted long before 1991.

The FRA recommends a simultaneous evacuation strategy with Grade D2 LD2 alarms:

The premise is recommended to have installed a Fire Alarm System installed meeting BS5839-6 designed to Category Grade D2 LD2, as per LACORS.

Grade D2 - A System of mains powered detectors with user-replaceable batteries.

Category LD2: a system incorporating detectors in all circulation areas that form part of the escape routes from the premises, and in all specified rooms or areas that present a high fire risk to occupants, including any kitchen and the principal habitable room.

I understand the system needs to be interlinked. However does this mean all the detectors in both flats and the communal hallway need to be linked, so they would all sound off together? 

Or does it mean we should have one flat's detectors linked to a detector in the communal hallway, and the second flat's detectors linked to another hallway detector? 

Thanks

This would only usually be required where fire resistance between flats is less than notional 30 minutes (wooden floor with good condition lath & plaster underdrawing) or confirmed 30 minutes fire resistance (wooden floor with good condition plasterboard underdrawing) - brand new very small blocks only require 30 minutes fire resistance rather than the usual 60.

The smoke control requirement for a stay put block wouldn't apply to a small ground floor only lobby either.

Often these small blocks require nothing beyond the front doors being fire doors where there is only a small lobby. These blocks often don't have a landlord supply so the cost implications of bringing in a new electrical supply for common fire alarms & emergency lighting etc. 

If you did require a common system it would be separate from the existing flat smoke/heat alarms spanning all three areas - flat, common areas & flats:

Thanks very much for replying.

I understand what you're saying about stay put, however my neighbours are keen to meet the FRA recommendations to show compliance now we've paid to have one done.

For an interlinked system for Grade D2 LD2 purposes, would it be sufficient to have an alarm in Flat 1 that is linked to a communal hallway alarm - and an alarm in Flat 2 that is separately linked to another second communal hallway alarm? This would ensure that any fire in the small communal hallway sets off the hallway alarms and the alarms in both flats. And a fire in the escape route of either flat would set off the communal hallway alarm, however it would not set off the alarm in the other flat.

Or do all alarms need to be interlinked, so that all 3 sound if 1 is triggered?

Put another way, does the interlinking of alarms just need to be between each individual flat to communal hallway; or does it need to be between both flats as well?

We can hardwire alarms into the hallway with no problem. We don't want a Grade A control panel as this is more onerous than Grade D that the FRA requires. 

I forgot to say I'm in England.

Thanks in advance, I've spent a long time researching but the guidance isn't partic clear for a lay person!

The thing is you can get the FRA done by someone else and they will disagree and support maintaining the status quo!

Your common system would be a Grade D smoke alarm in the common hall wirelessly linked to Grade D heat alarms in the flat hallways close to the bedroom doors. It would not link to each flats existing smoke alarms. This is to avoid the alarms being disabled or ignored by false alarms that would affect the whole building (a very common problem with simultaneous evacuation flat blocks). This doesn't mean you aren't allowed to link the whole lot, but be aware of the potential pitfalls of this!