What is an HMO?
A House in Multiple Occupation (HMO) is a property rented by three or more people who are not from one household (i.e., not a family) and who share facilities such as a kitchen or bathroom. HMOs include shared houses, bedsits, and some types of flat conversions.
From a landlord's perspective, HMOs offer significantly higher rental yields than single-let properties — often 1.5–2x the rent achievable from a single family. But the regulatory, planning, construction, and management requirements are substantially higher too.
Do you need planning permission to convert to an HMO?
This depends on the number of occupants and your local authority's approach.
Change of Use: C3 to C4
A standard family house falls within Use Class C3 (dwellinghouse). An HMO for 3–6 occupants falls within Use Class C4 (small HMO). In many parts of England, converting from C3 to C4 falls within Permitted Development Rights — meaning no planning permission is required.
However, many London boroughs and other high-demand areas have used Article 4 Directions to remove this Permitted Development Right. In these areas, you will need a full planning application to convert to an HMO even for 3–6 occupants.
Large HMOs (7+ occupants): Sui Generis
Properties for 7 or more occupants fall outside Use Class C4 and become sui generis (their own category). These always require a full planning application regardless of location.
Check with your local planning authority before purchasing a property for HMO conversion.
HMO licensing
HMO licensing is separate from planning permission and is managed by your local council.
Mandatory HMO licensing applies to properties that are:
- Rented to 5 or more people
- From 2 or more separate households
- With shared facilities
For mandatory licensed HMOs, you must apply for an HMO licence from your local council. Licences are typically granted for 5 years.
Additional and selective licensing schemes exist in many areas (particularly London) and can apply to smaller HMOs or all private rented properties. Check your specific local authority for active licensing schemes.
HMO licensing conditions: what you will need to comply with
To obtain and maintain an HMO licence, you will typically need to demonstrate compliance with:
Room size standards
Since October 2018, minimum room sizes for sleeping rooms in licensed HMOs are:
- Single adult: minimum 6.51 m²
- Two adults sharing: minimum 10.22 m²
- Children under 10: minimum 4.64 m²
Rooms below these sizes cannot be let as sleeping rooms.
Fire safety
HMOs have strict fire safety requirements under the Housing Act 2004 and associated guidance. Typically required:
- Grade D interlinked mains-powered smoke and heat alarms throughout
- Fire doors to all rooms opening onto escape routes (FD30 minimum)
- Self-closing mechanisms on all fire doors
- Emergency lighting (larger HMOs)
- Fire blanket and extinguisher in kitchen
- Fire risk assessment (recommended for all, mandatory for larger HMOs)
Kitchen and bathroom ratios
Local authorities apply minimum ratios for shared facilities. Common standards:
- One kitchen facility per 5 occupants (some councils require individual cooking facilities per room in larger HMOs)
- One bathroom/shower room per 5 occupants
- Separate WC recommended where bathroom has a bath
Heating, insulation, and energy efficiency
HMOs are subject to the Minimum Energy Efficiency Standards (MEES). Since April 2023, all new tenancies in the private rented sector in England and Wales require a minimum EPC rating of E. The government has consulted on raising this to C, which would significantly impact older HMO properties.
Conversion costs: what to budget
HMO conversion costs vary enormously by property type, starting condition, number of rooms, and specification. Here is a realistic range for different HMO types:
| HMO type | Typical conversion cost | Key cost drivers |
|---|---|---|
| 3-bed terrace → 3-room HMO | £12,000–£35,000 | Fire doors, alarms, kitchen upgrade |
| 4-bed semi → 5-room HMO | £25,000–£65,000 | Additional bathroom, fire upgrade, room reconfigurations |
| Large house → 7–10 room HMO | £60,000–£150,000+ | Full refurbishment, multiple bathrooms, commercial-grade kitchen |
| Purpose-built bedsit conversion | £120,000–£250,000+ | Full fit-out, en-suites, kitchenettes |
Major cost items to budget for:
- Fire doors: A standard FD30 fire door supply and fit costs £350–£600 per door. A 6-room HMO might need 8–12 fire doors.
- Fire alarm system: A Grade D addressable system for a 6-room HMO costs £1,200–£3,500 installed.
- Additional bathrooms: £5,000–£12,000 per bathroom.
- Room reconfigurations: If you need to create additional rooms, structural costs can range from £5,000 to £25,000+ depending on what walls are moved.
- Kitchen upgrade: A kitchen designed for multiple occupants may need more worktop space, additional sockets, and a larger appliance specification.
Building Regulations
Any material structural alteration, new bathroom, or change to fire safety provisions will require Building Regulations approval. For HMO conversions, relevant Parts include:
- Part B (Fire Safety): Escape routes, fire doors, alarm systems
- Part F (Ventilation): Adequate ventilation in bathrooms, kitchens, and sleeping rooms
- Part L (Conservation of Fuel and Power): Thermal performance of the building fabric
- Part G (Sanitation): Bathrooms and water supply
- Part P (Electrical Safety): All electrical installation work
Obtain either Local Authority Building Control (LABC) or private Approved Inspector sign-off for all notifiable work.
Timeline
A typical 3–5 bedroom HMO conversion project might take:
- Planning (if required): 8–13 weeks
- Building Regulations approval: 3–6 weeks (can run parallel)
- Construction: 6–16 weeks depending on scope
- HMO licence application processing: 4–12 weeks (varies significantly by local authority)
Start the licence application process early — some councils have significant backlogs.
Key risks
- Planning refusal: In Article 4 areas, councils actively limit HMO growth in some streets. Check the local plan before purchasing.
- Licensing delays: A property that cannot be legally occupied costs you rent while the clock runs.
- Build cost overruns: Discovery of damp, structural movement, or substandard existing electrics during conversion
- Condition non-compliance: Local authority inspections can require expensive remediation after licensing
- EPC C future requirements: Properties with poor insulation may need significant investment to meet tightening MEES standards
Summary
HMO conversion is a viable strategy for significantly increasing rental yield — but the planning, licensing, fire safety, and build quality requirements are substantial. Budget conservatively, engage a contractor experienced in HMO conversions, and check planning and licensing requirements with your specific local authority before committing to a purchase.