Converting a house into a house in multiple occupation (HMO) requires planning permission when the change crosses the threshold from a single household (Use Class C3) to an HMO of between 3 and 6 unrelated occupants (Use Class C4). In many areas, councils have removed this permitted change of use with Article 4 directions, making formal applications mandatory even for smaller HMOs.
Planning Signal holds around 11,000 HMO applications. This is one of the most politically sensitive residential categories. Local authorities in university towns and cities with high private rental demand are the most active, and approval rates vary more than almost any other application type.
The Use Class rules
The relevant use classes:
- C3: family home, single household. No planning permission needed to use as C3.
- C4: 3 to 6 unrelated occupants sharing facilities. Change from C3 to C4 is normally permitted development, but removed by Article 4 in many areas.
- Sui generis: 7 or more occupants. Always requires full planning permission. No permitted development rights.
Check whether your local council has an Article 4 direction before assuming you can convert without applying.
What councils assess
Where an Article 4 direction is in place, councils evaluate:
- The concentration of HMOs in the local area (many councils have a percentage threshold)
- Whether the property is in or near a defined HMO saturation zone
- Amenity standards: room sizes, shared facilities, natural light, ventilation
- Parking and cycle storage provision
- Impact on the character of the street and residential amenity of neighbours
Licensing alongside planning
Planning permission and HMO licensing are separate requirements. An HMO of 5 or more occupants over 3 storeys requires a mandatory HMO licence from the council. Many councils also operate additional or selective licensing schemes that cover smaller HMOs. Both must be in place before letting begins.
Failing to obtain a licence while holding planning permission does not prevent enforcement action. The two processes run in parallel.
Track HMO applications
Letting agents, landlords, and HMO conversion specialists can track new applications early to identify upcoming properties and understand local council policy shifts. Search planning applications near you or browse HMO planning applications across the UK.
For council approval rates and decision time data, visit planning statistics.