Small HMOs, Class C4 and the six occupant line

Class C4 of the Use Classes Order covers the use of a dwellinghouse as a house in multiple occupation by not more than six residents. Below three residents the property is not an HMO at all and remains C3. Above six it falls outside C4 and becomes sui generis, which means a full planning application with no permitted change available. So the class C4 HMO six occupants line is the one that decides whether a letting is a planning matter at all.

The second thing that decides it is whether the council has made an Article 4 direction. In much of the country the change from C3 to C4 is permitted development. In most university towns and in large parts of several cities it is not.

What Class C4 covers and the occupant range

The class picks up the definition of a house in multiple occupation from the housing legislation, with the converted block of flats category excluded. Broadly, that means a property occupied by three or more persons forming two or more households who share a basic amenity such as a kitchen, bathroom or toilet.

Two residents sharing are one or two households but do not meet the three-person threshold, so the property stays C3. Seven residents take the use outside C4 whatever the internal arrangement.

Counting matters more than most landlords expect. Residents means people living there, not tenancies. A couple occupying one room are two residents and one household. A property let to five people where one has a partner staying permanently is a six-resident property, and adding a lodger takes it to seven.

The permitted change between C3 and C4

Part 3 of Schedule 2 to the General Permitted Development Order 2015 permits change in both directions between C3 and C4. That two-way right is useful, because it means a property converted to a small HMO can revert without a further application, and the lawful use for the purposes of a later application is the one in place at the relevant time.

The right is a change of use right only. It does not authorise building works, so an extension or a loft conversion to create the extra rooms still needs its own route, and a rear dormer on designated land still needs permission.

Where the change is made in reliance on the right, keep evidence of the date. A certificate of lawfulness for an existing use is the way to fix the position if it is ever questioned, and it is far easier to obtain while the tenancy records are current.

Article 4 directions removing that change

An Article 4 direction made by the local planning authority withdraws the C3 to C4 permitted change in a defined area. Directions are common in university towns, and several cities have applied them across the whole authority area rather than to a single ward.

Three practical points.

Directions have boundaries, and those boundaries do not follow ward lines or postcode districts. Check the direction's own map for the individual property.

Directions have dates. Where a direction takes effect, a change made lawfully before that date is unaffected, which is why establishing the date of the change is worth doing at the time rather than in retrospect.

And a direction removes the permitted change, not the use class. The property is still C4 once lawfully in that use; what has gone is the free route into it.

Where the direction applies, a full planning application is needed, and the council will apply whatever concentration policy it has adopted.

Where seven or more occupants makes the use sui generis

A large HMO sits outside the Use Classes Order entirely. Moving from C4 to sui generis is a material change of use requiring permission, and there is no permitted route.

Councils assess those applications against concentration policy, amenity, parking and refuse, and they frequently condition the maximum number of occupants. Enforcement follows occupancy rather than paperwork, and an officer can establish numbers from licensing records, council tax, refuse volumes and, in the end, a visit.

The intermediate cases cause most trouble. A six-person C4 house that quietly takes a seventh occupant has changed use without permission, and the breach continues for as long as the occupancy does.

Licensing under the housing legislation as a separate regime

HMO licensing under Part 2 of the Housing Act 2004 runs alongside planning and answers a different question. Mandatory licensing applies to HMOs occupied by five or more persons forming two or more households, and councils may adopt additional licensing covering smaller HMOs in a designated area, or selective licensing covering other rented property.

A property can need a licence while remaining C3 in planning terms, and it can be C4 in planning terms without needing a licence. Neither decides the other, and a licence is not evidence that the planning use is lawful.

Licensing does bring mandatory conditions that affect layout. Minimum sleeping room sizes apply to licensed HMOs in England: broadly 6.51 square metres for one person over the age of ten, 10.22 square metres for two persons over ten, and 4.64 square metres for a child under ten, with rooms under 4.64 square metres not usable as sleeping accommodation. Check the current regulations, since the licence conditions and any additional local standards apply together.

Amenity standards and room sizes in planning terms

Planning applies its own standards, and they are not the licensing ones. Many authorities have adopted an HMO standards document covering room sizes, the ratio of bathrooms and kitchen facilities to occupants, communal space provision and refuse storage.

Where the council has such a document, design to it and say so in the Planning Statement. Where it has not, the assessment falls back on general amenity policy and on the national space standard by analogy, which is a weaker basis for both sides.

The question of whether part of a property has become a separate planning unit arises here too, particularly where a self-contained studio is created within the house, and our note on ancillary use and the separate planning unit covers that analysis.

Parking and bin storage evidence

These two items decide more small HMO applications than policy does.

On parking, a bare assertion that occupants will not own cars is worthless. Where the authority has a parking standard, apply it. Where on-street stress is the issue, a Parking Survey carried out to a recognised methodology, with overnight counts on a midweek and a weekend night outside school holidays, produces evidence an officer can use. Councils expect a suitably qualified author and professional review is advisable for anything contested.

On refuse, show the bin storage on the plan, sized for the number of occupants and the council's collection arrangements, in a position that does not require bins to be dragged through the house. Cycle storage in the same position helps the parking argument.

Check the Article 4 position for the specific address before relying on the middle row.

Establishing the existing lawful use of a let property

Where a property has been let to sharers for years without any application, the lawful use is whatever can be proved. Assemble tenancy agreements, rent records, council tax and any licensing history, and get statutory declarations from letting agents or long-standing tenants where the documents are thin.

A certificate of lawful existing use under section 191 of the Town and Country Planning Act 1990 is the only formal way to confirm that a use is lawful. It is decided on evidence rather than on merits, and it is the document a lender or a buyer will want.

Illustrative example: a six-bedroom terrace let to six students since 2015, in a street brought within an Article 4 direction in 2019. The use became C4 lawfully before the direction took effect. A section 191 certificate, supported by six years of tenancy agreements and council tax records, settles the position and removes the issue from the sale.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.

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