Beverly Danield

We live on the ground floor of a 3 storey purpose built block. All the homeowners have been contacted by the management company and told that they are legally required to replace their own front doors (which on each floor lead off a communal hallway) to a certain fire standard. The cost to be born by each owner. I recently heard that blocks under 4 storeys high are excempt. Or is this the responsibility of the management company?