The three limbs of Class C3 dwellinghouses
C3(a), (b) and (c) divide ordinary households, small care schemes and other six-resident groups. The tests turn on how the house functions, not on what the operating model is called.
Class C3 of the Town and Country Planning (Use Classes) Order 1987 has three limbs, and almost every argument about shared or supported housing turns on which one applies. Limb (a) covers use as a dwellinghouse by a single person or by people forming a single household. Limb (b) covers not more than six residents living together as a single household where care is provided. Limb (c) covers not more than six residents living together as a single household where no care is provided, other than a use falling within Class C4.
Read the three together and two words do the heavy lifting: household and care. Get either wrong and the use is not C3 at all, which means a change into it needs planning permission and a change out of it may too.
What each limb covers
Limb (a) is the ordinary case. A family, a couple, a lone occupier, a group of friends who really do function as one household. The parenthetical in the class, whether or not as a sole or main residence, means a second home or a holiday home occupied in this way is still C3(a).
Limb (b) is supported and small-scale care accommodation: a small children's home, a supported living house for adults with learning disabilities, a recovery house where personal care is provided. Up to six residents, living together as a single household, with care.
Limb (c) is the residual one. Up to six residents, single household, no care, and outside Class C4. It catches arrangements such as a small religious community or a group that does not meet the statutory definition of a house in multiple occupation.
Above six residents, or where the residents do not live together as a single household, the use falls into Class C2 residential institutions or becomes sui generis. Class C2 is a residential institution, which is a different thing again from the non-residential institutions in Class F1 covered in our note on Class F1 learning and non-residential institutions.
The single household test
There is no definition of household in the Use Classes Order itself, and councils generally work from the approach in housing legislation, where members of the same family, and certain relationships treated as family, form one household.
For limbs (b) and (c) the phrase is stronger than that. Residents must live together as a single household, which is about how the accommodation actually functions rather than about who signs which agreement.
Officers look for shared living and dining space used communally, shared cooking or catering, collective decision-making about the running of the house, and an absence of locks on individual rooms with separate tenancies for each. A building converted to six self-contained studios with separate front doors is not one household, whatever the operating model is called.
This is where a lot of supported accommodation proposals come unstuck. The care model is genuine and the planning description does not match the physical layout.
Care being provided to residents
Care has a definition in article 2 of the Order. It means personal care for people in need of it by reason of old age, disablement, past or present dependence on alcohol or drugs, or past or present mental disorder.
Two consequences follow. Housing management, tenancy support, help with benefits and floating support visits are not care, so a scheme offering those falls to be assessed under limb (c) or as an HMO rather than limb (b). And care provided to residents by a live-in carer does not turn the household into an institution if the six-resident ceiling and the single household test are both met.
Where care is provided to more than six residents, or where residents occupy on a basis that is not a single household, Class C2 applies and a full application is needed to get there from C3.
Where supported accommodation falls outside C3
The common patterns that take a scheme out of C3 are worth naming:
- More than six residents, however the rooms are arranged.
- Self-contained units with individual kitchens and bathrooms, which point to separate dwellings rather than one household.
- High turnover, short stays and emergency placements, which look institutional rather than domestic.
- Staff sleeping in and providing 24-hour cover, combined with the above.
- Residents having no communal life together and no shared facilities in practice.
None of these is decisive alone. Together they move a scheme towards C2 or sui generis, and the assessment is a matter of fact and degree on the evidence.
The related question of when part of a property becomes a separate planning unit is covered in our note on ancillary use and the separate planning unit, and it is the same analytical exercise.
| Arrangement | Likely class | Route from an existing house |
|---|---|---|
| Family or single household | C3(a) | No change |
| Up to six sharing with care, one household | C3(b) | No permission needed from C3(a) |
| Up to six sharing, no care, meeting the HMO definition | C4 | Permitted change unless removed by direction |
| Seven or more sharing | Sui generis | Full application |
| Care accommodation above six residents | C2 | Full application |
Treat the table as a starting point. The local validation checklist and any adopted policy on concentration take precedence.
Evidence about occupation arrangements
Because the class turns on how people live, the application has to describe that in concrete terms. A statement that says the property will be used as C3(b) supported living tells a case officer nothing they can rely on.
Set out the number of bedrooms and their sizes, the communal rooms and their areas, the catering arrangement, the staffing pattern including any sleep-in cover, the anticipated length of stay, the tenure under which residents occupy, and the care registration position with the regulator where applicable. Where the operator is a registered provider, say so.
A Planning Statement that carries this detail and then applies the limbs of the class to it is the difference between a delegated approval and a request for further information. Add a floor plan marked with communal and private space, because officers read plans faster than paragraphs.
For schemes involving adaptation, the access arrangements need their own treatment in a Design and Access Statement, covering step-free entry, circulation widths and the accessible WC provision that supported occupancy usually needs.
Conditions restricting occupation
Where permission is granted for a use at the margin of the class, expect a condition. The common forms cap the number of residents, tie the permission to a named category of occupier, or restrict the use to the particular limb applied for.
A numbers condition is the one to negotiate with care, because the business plan depends on it and varying it later means a section 73 application. Where the operating model may change, argue for a condition drafted by reference to the class rather than to an operator, since personal permissions expire with the operator.
Conditions removing permitted change rights also turn up. A condition preventing a later change from C3 to C4 without permission is lawful and increasingly common in areas with concentration policies.
Council tax and licensing sit outside planning
Two regimes run alongside and neither decides the planning class.
Licensing under Part 2 of the Housing Act 2004 applies to houses in multiple occupation meeting the statutory tests, with mandatory licensing for larger HMOs and additional or selective licensing where a council has adopted it. A property can need an HMO licence while remaining C3 in planning terms, and it can be C4 in planning terms without needing a licence.
Council tax treatment of houses in multiple occupation changed in December 2023, so that most HMOs are valued as a single dwelling rather than banded room by room. Useful commercially, irrelevant to the use class.
Illustrative example: a four-bedroom house proposed as supported living for five adults with learning disabilities, with a shared kitchen and living room, one sleep-in staff room, and care provided by a registered provider. That is C3(b), no permission is needed from C3(a), and the sensible step is a certificate of lawfulness for a proposed use so the funder has something in writing. Convert the same house into five studios with kitchenettes and the answer changes completely.
This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. A lawful development certificate is the only formal way to confirm that a use is lawful. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.
Enter your postcode on PlanScope to see which reports a supported or shared housing proposal is likely to need.
Frequently asked questions
What is the difference between C3(b) and C3(c)?
Both cover up to six residents living together as a single household. Limb (b) applies where care is provided to residents, using the definition of care in article 2 of the Use Classes Order. Limb (c) applies where no care is provided and the use is not within Class C4, which catches arrangements that fall outside the statutory definition of a house in multiple occupation.
Does housing-related support count as care?
No. Care is defined as personal care for people in need of it by reason of old age, disablement, past or present dependence on alcohol or drugs, or past or present mental disorder. Tenancy support, help with benefits and floating support visits fall outside that, so a scheme offering only those is assessed under limb (c) or as an HMO.
How do councils test whether residents form a single household?
By how the accommodation functions rather than by the operating model. Officers look for communal living and dining space in genuine shared use, shared cooking or catering, collective running of the house, and the absence of self-contained units with individual tenancies. Six studios behind one front door are not one household.
Does an HMO licence change the planning use class?
No. Licensing under Part 2 of the Housing Act 2004 and the Use Classes Order are separate regimes with separate tests. A property can need an HMO licence while remaining C3 for planning purposes, and it can be C4 for planning purposes without needing a licence. Neither answer decides the other.
When does supported accommodation become Class C2?
When care is provided to more than six residents, or when the residents do not live together as a single household. Self-contained units, high turnover, emergency placements and round the clock staffing all push a scheme towards a residential institution. Getting there from C3 needs a full planning application.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.