HMO Conversions in London: Licensing, Planning, Standards and Costs

Under the Housing Act 2004, a House in Multiple Occupation is a property occupied by 3 or more people forming more than 1 household, who share facilities (bathroom, toilet, kitchen). The legal definition is precise; the practical definition is a property let to 3 or more unrelated individuals each renting their own room, with shared kitchen and bathroom facilities.

Large HMOs (5 or more people from more than 1 household) require a mandatory HMO licence in all English local authorities. Smaller HMOs (3 to 4 people) may require licensing under the local authority's Additional Licensing scheme — many London boroughs have extended licensing to cover 3 and 4-person HMOs. Check with the specific borough before proceeding.

Mandatory HMO Licence: required for any HMO housing 5 or more people from 2 or more households in a building of 3 or more storeys (or, following the 2018 changes to mandatory licensing, in any building regardless of height if it houses 5+ people from 2+ households).

Additional Licensing: each London borough has its own Additional Licensing scheme (or lack thereof). As of 2026, most London boroughs — including Newham (100% of HMOs), Waltham Forest, Brent, Haringey, Tower Hamlets, Southwark, Hackney, and many others — have Additional Licensing covering 3 and 4-person HMOs. Check the specific council's website.

Licence conditions typically require:

• Minimum room sizes (see below)
• Adequate fire safety measures (alarms, fire doors, escape routes)
• Adequate kitchen and bathroom facilities per number of occupants
• Ongoing management standards (gas safety, electrical inspection, EPC)
• The property to be managed by the licence holder or a named manager

Licence fees: vary by borough. Typical range £500 to £1,500 per licence. Licences are usually granted for 5 years.

Changing the use of a property to an HMO is a material change of use and may require planning permission:

C4 Use Class (Small HMO, 3-6 people): in many London boroughs, properties changing use from a standard dwelling (C3) to a small HMO (C4, 3-6 people) can do so via Permitted Development rights. However, many London boroughs have removed this PD right via Article 4 Direction — requiring full planning permission for any change of use to C4.

Sui Generis (Large HMO, 7+ people): any HMO with 7 or more occupants is sui generis (outside use classes) and always requires full planning permission.

Check your borough's Article 4 position: in London, the following boroughs (among others) have Article 4 Directions removing PD C3-to-C4 change of use: Newham (entire borough), Waltham Forest, Haringey, Brent, Tower Hamlets, Hackney, Lewisham, Wandsworth, and others. Before progressing any HMO conversion, check your specific borough's planning portal.

The government's national minimum space standards for HMOs (updated 2018) set minimum room sizes:

• Single occupant sleeping room: minimum 6.51m²
• Double/two-person sleeping room: minimum 10.22m²
• Room for a child under 10: minimum 4.64m²
• Living room / kitchen-diner: proportionate to the number of occupants

Many London boroughs set higher standards in their Additional Licensing conditions. Always check the borough's specific requirements.

In practice: rooms of 7 to 8m² are functional but not desirable. Investing in better room sizes (8 to 12m² minimum for single rooms) produces higher quality tenants, lower voids, and stronger rental values. The best London HMOs create rooms of 10 to 14m² with en-suite facilities.

Fire safety is the most critical compliance area for HMOs. Requirements vary by size and height but typically include:

• L2 or L1 fire alarm system: interconnected smoke and heat detectors throughout all habitable rooms, communal areas, kitchens, and escape routes. Grade A system (mains-powered with battery back-up) required for larger HMOs.
• Emergency lighting: in communal corridors and stairways in larger or multi-storey HMOs.
• Fire doors (FD30S): on all room doors off the escape route, kitchen doors, and (in some configurations) doors to individual rooms. Self-closing devices on all fire doors.
• Protected staircase: in a three-storey or taller HMO, the staircase must typically be a protected escape route with fire-rated construction on all sides.
• Thumb-turn locks: all exit doors must be operable from inside without a key.

The fire safety strategy should be designed by a competent person and agreed with the licensing authority before conversion work begins.

Costs depend heavily on the condition of the property, the number of rooms being created, and the specification level:

• 3-bedroom house converted to 4 or 5-bed HMO (room additions in loft, new bathrooms, full refurbishment): £45,000 to £80,000
• Full HMO conversion of a 4-bed terrace to 6-bed with en-suites, full compliance package: £70,000 to £120,000
• Full conversion of a larger property to 8+ bed HMO with en-suites, fire safety system, compliance refurbishment: £120,000 to £220,000+

Key cost components:

• Loft conversion (to create additional rooms): £35,000 to £65,000 additional
• En-suite installations per room: £5,000 to £12,000 each (first-fix and second-fix, including drainage)
• Fire alarm system (Grade A, L2): £3,000 to £8,000
• Fire doors and closers (per door): £300 to £700
• Emergency lighting: £1,000 to £3,000
• Full rewire: £5,000 to £12,000
• Planning application (if required): £578 (change of use, 2026 fee in England)
• HMO licence fee (varies by borough): £500 to £1,500