Part 1 of the Housing Act 2004 (HA 2004) introduced a new system for the enforcement of local housing standards. This framework was based on an assessment of hazard in homes and provided local authorities with a new set of enforcement powers including to serve improvement notices (HA 2004, ss 11–12). The parameters of the housing health and safety rating systems (HHSRS) are set out in HA 2004, s 1. It is framed as a system to assess the condition of ‘residential premises’, and for the enforcement of housing standards in relation to such accommodation (HA 2004, s 1(1)). ‘Residential premises’ is defined as covering a dwelling, a house in multiple occupation (HMO), an occupied HMO and any common parts of a building containing one or more flats (HA 2004, s 1(4)). ‘Dwelling’ is in turn defined as meaning a building or part of a building occupied or intended to be occupied