fire break in 1900s open loft Terrace

Section62

https://forums.moneysavingexpert.com/discussion/comment/82176946#Comment_82176946

Bottom line is the meaning of "We need to have a fire barrier constructed between our house and adjoining neighbour".

If this is a requirement of an insurer or housing/BC enforcement then it needs to be done correctly regardless of the 'reclusiveness' of the neighbours.

Strictly the work should probably be signed off by building control, but as a minimum be compliant with building regs.

If the OP's insurers want a fire barrier, but only half a fire barrier is constructed, then the insurers will have grounds to wriggle out of liability if a relevant claim gets made in the future.

TBH this is the kind of thing where you need to get past any neighbour reluctance and do the job properly, rather than settling for a bodge. Fires kill people.