A House in Multiple Occupation (HMO) is where at least 3 tenants live, forming more than one household, and share facilities (kitchen, bathroom, etc.). They are often used for students, young professionals, or low-income tenants.

Planning Use Classes for HMOs C4 Use Class is a small HMOs (3–6 unrelated occupants). C3 Use Class is a Dwelling houses (single households or small families. Sui Generis HMOs are larger HMOs (7 or more occupants).

Sui generis" means "in a class of its own" – i.e. not covered by standard use classes.Because of this, planning permission is always required to convert a property into a large HMO (7+ occupants).

Suis Generis matters as Councils have more control over larger HMOs due to potential impacts on neighbourhoods, parkig and straffic ussues, noisse rubbish and anti-social behaviour and loss of family housing stiock

Article 4 Directions allow councils to remove permitted development rights for smaller HMOs (C3 → C4), meaning permission is required even for small conversions. For sui generis HMOs, Article 4 isn’t needed because permission is already required. Local Plans and Supplementary Planning Documents (SPDs) often set out criteria for approving or rejecting HMO proposals (e.g., limits on concentration per street, minimum space standards). It should also be noted that susi genberis use requires a lot more work in terms of building regualtions as the proety will be views as a hotel in terms of fite safety and approved documet B fire safety.

Practical Example A landlord wants to convert a 5-bed family house into a 10-bed student HMO. Because it’s 7+ occupants, this is sui generis. They must apply for full planning permission.The council will assess: parking availability, bin storage, room sizes, effect on neighbours, and local HMO density.

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