HMO Conversion in London: Planning, Licensing & Building Requirements

Houses in Multiple Occupation (HMOs) — properties let to three or more unrelated tenants sharing facilities — are a significant part of London's rental market. Converting a family house to an HMO can increase rental yield substantially, but the planning, licensing, and building requirements are more complex than standard single-let properties.

Planning Permission for HMO Conversion

In London, almost all HMO conversions require planning permission. A change of use from C3 (dwellinghouse) to C4 (small HMO — 3 to 6 unrelated occupants) was previously permitted development in many areas, but Article 4 directions have been applied by almost every London borough to remove this PD right. Check with your specific borough before assuming PD applies.

Large HMOs (7+ occupants, Sui Generis use class) always require full planning permission.

Planning considerations include:

• Impact on housing mix in the area
• Parking and cycle storage
• Waste and refuse management
• Design and appearance (if external changes are involved)
• Amenity impact on neighbours

HMO Licensing

Mandatory HMO Licensing applies to HMOs with 5 or more persons in 2 or more households sharing facilities, across 3 or more storeys. A mandatory licence must be obtained from the local authority before letting.

Additional HMO Licensing is operated by many London boroughs to cover smaller HMOs (3–4 persons, 2 storeys). Check your borough's licensing scheme — most London boroughs operate additional licensing schemes.

Licence conditions typically specify:

• Minimum room sizes (10m² for a single adult room is the national minimum under the Housing Act 2004 amendment)
• Fire safety standards (fire doors, fire alarm system, emergency lighting)
• Adequate cooking, bathroom, and toilet facilities relative to occupant numbers
• Condition and management standards

Building Regulations for HMO Conversion

A change of use to HMO requires a Building Regulations application. Key requirements include:

Fire safety (Part B):

• Fire alarm system (Grade D minimum, typically Grade A for larger HMOs)
• Fire doors to all rooms (typically FD30S)
• Emergency lighting in escape routes
• Fire stopping where services penetrate compartment walls

Means of escape (Part B):

• Protected escape route from all floors
• Window egress from habitable rooms where applicable

Ventilation (Part F):

• Adequate ventilation in all rooms and shared facilities

Sound insulation (Part E):

• Where internal partitions are created or altered, sound insulation to the revised standards

Typical Costs of HMO Conversion

A full HMO conversion of a 4-bedroom house to a 5–6 bedroom HMO in London typically costs £30,000–£70,000 depending on the existing condition, fire safety works required, bathroom additions, and specification.

RCB Design & Build

RCB Design & Build delivers HMO conversion projects across London — from planning and licensing advice coordination through to full construction and Building Regulations compliance.