Roof voids in older blocks of flats

[mosh]

Where can I find information about lack of compartmentation within roof voids of older blocks of flats that pre dates modern building regs? I.e. information that can provide advice as to what sort of requirements there are for retrofitting compartmentation?

Thanks

[AnthonyB]

Both Government risk assessment guides (small purpose built flats & purpose  built flats in general) indicate minimum expectations.

[mosh]

Thank you.