Class C4 and the C3 to C4 change: small HMOs

Class C4 covers a small house in multiple occupation: between three and six unrelated people sharing basic amenities such as a kitchen or a bathroom. Moving a family house from Class C3 into Class C4 is permitted development under Class L of Part 3 of Schedule 2 to the GPDO 2015, so no planning application is needed. Unless the council has made an Article 4 direction, which in a great many university towns and inner suburbs it has.

That one check decides whether your conversion is a weekend of joinery or a three month planning application.

What Class C4 actually covers

The Use Classes Order takes the meaning of a house in multiple occupation from section 254 of the Housing Act 2004. In practical terms the property is C4 when three, four, five or six occupiers who do not form a single household live there and share at least one basic amenity.

Above six occupiers the use is sui generis and always needs planning permission. Purpose built student accommodation is a separate question again and usually sui generis.

Two features of Class C4 are worth holding onto. It is a use class, not a licensing category, so a property can be C4 in planning terms while needing no HMO licence, and it can need a licence while the planning position is disputed. And the class is about occupation, not about layout, so a house with six bedrooms let to a single family remains C3.

The permitted change under Class L

Class L of Part 3 permits change of use from C4 to C3, and from C3 to C4, in both directions. No prior approval, no notification, no fee.

Where it operates, the practical effect is that the planning system does not engage at all with the conversion. The Building Regulations still do, HMO licensing still does, and the freeholder or mortgage lender may still have something to say.

Where the right has been withdrawn, you need express planning permission for the change of use, and the application is judged against the adopted local plan like any other.

Article 4 directions, and how to check for one

An Article 4 direction is made by the local planning authority over a defined area and removes a specified permitted development right within it. HMO directions almost always remove the C3 to C4 direction of Class L while leaving C4 to C3 intact, so you can always convert back.

Check three places before you exchange contracts.

• The council's own planning policy pages, which publish the direction, the map and the confirmation date.
• The national planning data service at planning.data.gov.uk, which holds Article 4 direction datasets.
• The council's local plan and any HMO supplementary planning document, because the direction and the policy that will be applied to your application are separate documents.

Directions are geographically precise and the boundary often follows individual streets. Two houses opposite one another can sit on different sides of it. Never rely on a general statement that a town "has an Article 4 for HMOs" without checking the address.

Where a direction exists, it does not make existing lawful C4 uses unlawful. A property already in lawful C4 use when the direction took effect keeps that use. Proving it is the difficulty, which is why a lawful development certificate under section 191 is worth obtaining while the evidence is still fresh.

What a C4 application has to answer

Councils in Article 4 areas usually assess four things, and the weighting between them is set by local policy rather than national policy.

Concentration comes first. Many authorities apply a threshold expressed as a proportion of HMOs within a stated radius of the application property, and some add a rule against creating an unbroken run of HMOs or leaving a family house sandwiched between two of them. The thresholds and radii vary, so read the adopted policy rather than assuming a figure.

Amenity for occupiers comes second: room sizes, the retention of a communal living room, kitchen capacity relative to the number of occupiers, and outdoor space.

Amenity for neighbours comes third, meaning noise, refuse storage and the visual effect of bins and cycles on the frontage.

Parking comes fourth, and it is where most applications are won or lost in streets that are already full. Assertion carries no weight here. A parking survey carried out to a recognised methodology, on the right nights and outside holiday periods, is the evidence an officer can actually use.

Pull all four together in a planning statement that addresses the policy tests in the council's own order, with a room schedule giving floor areas, a bin and cycle store shown on the plan, and a short management statement covering who manages the property and how.

Room sizes, licensing and the other regimes

Planning is one of four systems and the others do not wait for it.

Mandatory HMO licensing applies to properties occupied by five or more people forming two or more households, whatever the number of storeys. Many councils also run additional licensing schemes catching smaller HMOs, so check the local position.

The mandatory licence conditions set minimum sleeping room floor areas: 6.51 m² for one person aged over 10, 10.22 m² where two people over 10 share, and 4.64 m² for a child under 10. Rooms below 4.64 m² cannot be used as sleeping accommodation. Councils commonly apply their own, larger, standards through licensing policy and through planning.

The Building Regulations bring fire separation, means of escape and alarm systems under Approved Document B, and sound insulation under Approved Document E where the works create separation between rooms in different occupation. Work that needs no planning permission can still need building control approval and a fire risk assessment.

Council tax, energy performance and, where relevant, the freeholder's consent all sit outside planning as well.

Illustrative example: an investor buys a four bedroom terrace intending a five bed C4 let. The street is inside an Article 4 area, the ground floor reception room was to become the fifth bedroom, and the council's HMO policy requires a retained communal living space. Keeping the reception room and letting four rooms made the application straightforward. The fifth bedroom would have made it a refusal.

Timing, evidence and the cost of getting it wrong

Do the checks in this order, and do them before you commit.

1. Confirm the Class C4 position and whether an Article 4 direction covers the exact address.
2. Read the adopted HMO policy and any supplementary planning document, and work out where the property sits against the concentration threshold.
3. Check the licensing position with the housing team, since it is a different department from planning.
4. Only then price the works.

If you have already converted and the Article 4 was in place, do not assume time will fix it. The Levelling-up and Regeneration Act 2023 moved enforcement time limits in England towards a single ten year period, so check the current position and the commencement date rather than relying on the older four year rule for changes of use. A retrospective application, submitted before the council writes to you, is usually a better place to start than a planning contravention notice.

This is general guidance rather than legal advice. A lawful development certificate is the only formal way to confirm that a use is lawful, so check the position with your local planning authority or a qualified professional before relying on it.

Enter your postcode on PlanScope to see which supporting documents a C4 change of use application is likely to need. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.