Hi,

I own a flat in a converted Victorian terrace comprising of 3 flats on separate floors with a communal entrance, hallway and staircase, and a 4th flat in the basement with its own entrance. in late 2023  we commissioned a fire alarm system, which was completed in early 2024. The surveyor had recommended an Ld2 system. The zoning was split into 2 zones. 1 zone is the basement flat, and the second zone are the 3 flats with the separate entrance and staircase. We recently had the annual maintenance check, and the fire safety rep stated that we should have had 4 zones. I know that the total floor area of the 3 flats combined into 1 zone are less than 300m squared, is the zoning correct as is or do we have to change zoning? Further more LD2 requirements state that heat sensors be located 600mmm inside the entrance  lobby of each flat, smoke sensors were installed instead, is this Ok?

If you are under 300 sq.m. then a single zone for the whole building or over more than one storey is compliant, the only exception would be a HMO or Sheltered Housing where zoning per room/dwelling is recommended regardless of the size. A non Building Regs flat conversion can be classed as a HMO under s257 of the Housing Act if at least two thirds rental, but this is mainly an administrative definition to allow these premises to require licensing should a council wish to as part of an additional licensing scheme and not for specific fire precautions reasons. It can be beneficial to zone further but isn't needed to meet BS5839 recommendations so unless an addressable system (which can easily and cheaply be rezoned by programming) I wouldn't bother as you would need recabling.

The reason for heat detection on flat hallways is to prevent the whole building being disrupted by false alarms that could be generated by smoke detection as the common system is to protect people in the rest of the building, not the flat of fire origin. In this case each flat would still need local smoke alarms to protect the flat residents - a false alarm in these would only disrupt the flat causing it. It's possible for a common system to do double duty by having a smoke instead of a heat and no separate local smoke alarms - if there are no false alarm issues then this is fine.