In a retirement complex with 67 flats we have recently had a fire alarm system upgrade. We have had a new fire panel, removed fire bells from flats as the fire risk assessment said as we are a stay put site we shouldn't have them and replaced the bells in the corridors with sounders. Existing cabling was used. Where the bells have been removed from the flats the remaining cable has been joined using plastic choc blocks. These are (mostly) inside the existing round metal conduit junction box but without a lid. This is fixed to the wall and the plaster board is dabbed onto the wall leaving a gap between. Then on the flat side (apartment side) of the plaster board a metal plate has been fitted using the fixing holes of the original junction box. This results in a gap between this plate and the upper edge of the junction box. The installer says this is still classed as an enclosed metal box as fire cannot get in. Is it? Is it a fire proof situation? Is the system compliant? We have a modifications certificate.

BS 5839-1:2025 is fairly clear on this point.

The standard states that external joints should be avoided wherever practicable, but where they are necessary, the jointing method and terminals need to be capable of withstanding a similar temperature and duration to that of the cable itself. In other words, the joint shouldn’t become the weak point in the fire-resisting cable system.

It also requires joints outside system components (panels, detectors, MCPs, sounders etc.) to be enclosed in suitably labelled junction boxes, with the intention being that they remain identifiable and maintain integrity during fire conditions.

That’s why you’ll commonly see:

• metal junction boxes

• ceramic terminal blocks

• fire-resistant terminals/fixings

used on life safety systems, rather than generic plastic choc-boxes or floating connector strips above ceilings.