Converting a London Property to an HMO 2025: Licensing, Planning, Fire Safety, and Costs

There are two types of HMO licensing that may apply to a London property being converted to an HMO: Mandatory HMO licensing: applies nationally to all HMOs that are occupied by 5 or more persons forming 2 or more separate households, in a property of 3 or more storeys. Since 1 October 2018, the 3-storey requirement was removed by the Licensing of Houses in Multiple Occupation (Mandatory Conditions) (England) Regulations 2018 — mandatory licensing now applies to all HMOs occupied by 5 or more persons forming 2 or more separate households, regardless of the number of storeys. This means: a 4-bedroom, 3-bathroom house in London let to 5 sharers as an HMO requires a mandatory HMO licence from the local authority. Additional HMO licensing (borough discretion): many London boroughs have designated all or part of their borough as an Additional Licensing area under Section 56 of the Housing Act 2004, requiring all HMOs (below the mandatory threshold — 3 or 4 occupants as well as 5+) to be licensed. As of 2025, the majority of inner London boroughs operate additional HMO licensing (including Islington, Hackney, Tower Hamlets, Southwark, Lambeth, Lewisham, and others). Check the specific borough's website to determine whether additional licensing applies to the property. HMO licence application: applied for with the relevant London borough. The licence application requires: completion of the application form; payment of the licence fee (varies by borough and by HMO size — typically £300-£1,200 for a 5-bedroom HMO, depending on the borough); submission of supporting documents (gas safety certificate, EICR, Energy Performance Certificate, details of the proposed management arrangements, fire risk assessment, floor plan); confirmation of the HMO management and safety arrangements meeting the borough's licensing conditions. Licence duration: HMO licences are typically granted for 5 years, subject to continued compliance. The licence is not transferable — if the property is sold, the new owner must apply for their own licence. HMO licence conditions: when an HMO licence is granted, the LHA attaches conditions to the licence — typically covering: minimum room size standards (see below); fire safety measures (fire doors, fire detection system, emergency lighting, means of escape); management standards (inspection and maintenance of the property); gas and electrical safety certification; anti-social behaviour management; waste and recycling management. Failure to comply with licence conditions is a criminal offence. Operating a licensable HMO without a licence is a criminal offence carrying an unlimited fine, and the LHA can issue a Rent Repayment Order (RRO) requiring the landlord to repay up to 12 months' rent to the tenants.

The conversion of a residential property from a single-family dwelling (Class C3) to a small HMO (up to 6 unrelated residents sharing — Class C4) was, until recently in many London boroughs, permitted development — no planning permission was required. Since 2010, under Article 4 Directions made by many London boroughs, this PD right (to convert from Class C3 to Class C4 HMO without planning permission) has been removed in large areas of London. An HMO with 7 or more residents is not classified as Class C4 — it is a sui generis use. The conversion of any dwelling to a sui generis HMO always requires planning permission (there is no PD right for conversion from C3 to sui generis). How to determine whether planning permission is required for an HMO in London: Step 1: check whether an Article 4 Direction removing the Class C3-to-C4 PD right applies in the area where the property is located. The borough's planning department website will list Article 4 Directions. In most inner London boroughs, and in many outer London boroughs, this Article 4 Direction covers the entire borough or most of the residential areas within it. Step 2: if an Article 4 Direction applies, a planning application for change of use from Class C3 (single-family dwelling) to Class C4 (small HMO) must be submitted. The LPA assesses the application against: the local plan policy on HMO concentrations; the NPPF guidance on mixed and balanced residential communities; the impact on the character of the area and the amenity of neighbours (noise and disturbance from a higher-occupancy use, bin storage, cycle storage, parking). Step 3: if the HMO will have 7 or more residents (sui generis): a planning application is always required, regardless of Article 4. Assessment against local HMO concentration policies is typically more rigorous for sui generis HMOs. HMO concentration policies: many London boroughs have adopted planning policies setting a maximum concentration of HMOs within a given area — typically expressed as a maximum percentage of HMO within a defined zone. For example, a policy might state that planning permission for a new HMO will be refused where HMOs already comprise more than 10% (or 20%, or 25% — the threshold varies by borough) of the residential dwellings within 50 or 100 metres of the application site. Always check the local plan HMO concentration policy before investing in a property for HMO conversion in London.

Fire safety requirements for London HMOs: fire safety in an HMO is regulated by: the HMO licence conditions (set by the local housing authority — LHA); the Housing Health and Safety Rating System (HHSRS — Part 1 of the Housing Act 2004); the Regulatory Reform (Fire Safety) Order 2005 (RRO), which applies to the common parts of the HMO (hallways, staircases, landings). A fire risk assessment by a competent person is required for the common parts of every HMO. Key fire safety measures required for a typical London 4-5 bedroom HMO: fire detection: a Grade D, Category LD1 or LD2 system — mains-powered, battery-backup, interlinked smoke alarms in every habitable room and on every landing and hallway, plus a heat alarm in the kitchen. The exact specification is set by the LHA as a licence condition. Fire doors: FD30S fire doors (with self-closing devices, intumescent seals, and cold smoke seals) on all room doors opening onto the escape route hallway and staircase, on the kitchen door, and on the door to any under-stair storage area. Emergency lighting: emergency lighting (non-maintained luminaires in the escape routes, illuminated for at least 3 hours in the event of a mains power failure) is required in the common parts of most HMOs of 3 or more storeys or where the escape route is a single direction without natural light. Room size standards (HMO licence conditions): the Licensing of Houses in Multiple Occupation (Mandatory Conditions) (England) Regulations 2018 set minimum room size standards as part of the mandatory licensing regime (as of October 2018): minimum floor area for a room used as sleeping accommodation for one person aged 10 or over: 6.51 sq m (GIA, including the area under the roof slope down to 1.5m above floor level); minimum floor area for two persons sharing: 10.22 sq m. Rooms below 4.64 sq m cannot be used as sleeping accommodation at all. Many London boroughs set higher minimum room size standards in their additional licensing conditions (typically 10 sq m for a single occupancy room). Conversion costs for a London 4-bedroom to 5-bedroom HMO (indicative all-in refurbishment cost, 2025): a typical conversion of a 4-bedroom London terrace (originally a single let) to a 5-bedroom HMO includes: ensuite bathrooms to each bedroom (adding value and enabling per-room rents): each new ensuite (partition, shower tray, vanity basin, WC, tiling, M&E connections): £4,500-£9,000 per ensuite, depending on specification. Fire safety upgrade (Grade D LD2 interlinked fire alarm system, FD30S fire doors to all bedrooms and kitchen, emergency lighting on escape route): £2,500-£6,500. Electrical upgrade (new consumer unit if required, additional circuits for new ensuites, smoke alarm circuit, emergency lighting circuit): £2,000-£5,000. Refurbishment of shared kitchen (full kitchen refit to high-specification — robust and easy to clean finish — for 5 sharers): £6,000-£12,000. Broadband, TV aerial, and data connections to each bedroom (increasingly a strong rental differentiator): £500-£2,000. Decoration and floor finishes throughout: £3,000-£8,000. External bin storage (a licence condition in most London boroughs): £500-£2,000. Total all-in HMO refurbishment cost (London 2025, for a 4-5 bed terrace): £25,000-£60,000 depending on starting condition, number of ensuites, and specification level.