There is no set time for doing this. The IET recommends a ‘no more than’ period depending the type of the premises. See the table below for some examples.
It should be noted that if there is a case of a dispute, the IETs recommendations will be taken very seriously by a court.
Very often local authorities will also have their own rules on how often this should happen, e.g. no more than 12 months in HMOs.
