Converting a family home into a house in multiple occupation (HMO) doesn’t always require planning permission — but Article 4 Directions in many cities mean it does. Here’s how to work out what applies to your property.
Converting a single family home (Class C3) to a small HMO of 3–6 people (Class C4) is permitted development under Part 3, Class L of the GPDO 2015 — no planning application needed. However, many councils in cities, university towns, and areas with high HMO concentrations have made Article 4 Directions removing this right, meaning a full planning application is required. Large HMOs (7+ people) are “sui generis” and always need planning permission. HMO licensing is a separate legal requirement from planning.
Under the Town and Country Planning (Use Classes) Order 1987 (as amended), Class C3 covers a house occupied by a single family or up to 6 people living as a single household. Class C4 covers a small HMO — a house occupied by 3 to 6 unrelated people who share facilities but are not a single household. Sui generis covers HMOs with 7 or more occupiers, which always require planning permission for any change of use.
The change of use from C3 (dwellinghouse) to C4 (small HMO) and back is permitted development under Part 3, Class L of the GPDO 2015. Where no Article 4 Direction has removed the right, you can convert a house to a small HMO without any planning application.
Many councils in cities, university towns, and areas with high HMO concentrations have made Article 4 Directions removing the C3-to-C4 permitted development right. Where an Article 4 Direction applies, planning permission is required. The council will assess the application against its HMO policy — typically a threshold-based approach that refuses where HMOs already exceed a certain percentage in the immediate area.
An HMO with 7 or more occupiers falls outside the use classes — it is sui generis and always requires planning permission. Converting a C4 small HMO to a large HMO (adding a 7th bedroom) also constitutes development requiring planning permission — it’s a change from C4 to sui generis.
HMO licensing is separate from planning and applies regardless of whether planning permission was needed. Mandatory HMO licences are required for HMOs with 5 or more occupiers in buildings of 3 or more storeys. Some councils have additional licensing schemes covering smaller HMOs. Operating an unlicensed HMO is a criminal offence, and tenants can apply for a rent repayment order to reclaim up to 12 months’ rent.
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