Common parts include entrance halls, staircases, landings, corridors, lobbies, bin stores, plant and meter rooms, communal lofts and shared external escape routes. In blocks of flats the position goes further: the Fire Safety Act 2021 confirmed that the assessment must also cover the structure, the external walls including cladding and balconies, and the flat entrance doors, even though those doors open into private homes. Maisonettes with their own street doors are the classic edge case: where each home is entered directly from the street and nothing else is shared, the duty does not arise.
HMOs sit firmly inside the duty because shared kitchens, bathrooms and landings are common parts by definition, and HMO licensing layers its own fire safety conditions on top. Where the duty applies, it is normally discharged through a Type 1 fire risk assessment of the shared areas, commissioned by the responsible person for the building.