An annexe for a dependent relative and its conditions
Separate metered supplies, a separate gate and a fenced garden turn an annexe into a second dwelling. What to show on the plans, and which condition wording to ask for.
A granny annexe planning permission turns on one question: is the accommodation ancillary to the main house, or is it a separate dwelling? Get that wrong and you have created a new planning unit without permission, with an enforcement risk and a problem on sale. Councils decide it on the physical and functional relationship rather than on the family arrangement, and they attach conditions designed to keep the answer stable for as long as the building stands.
The family circumstances matter less than most applicants expect. The building, the access and the services matter more.
Ancillary accommodation against a separate dwelling
Section 55 of the Town and Country Planning Act 1990 makes a material change in the use of land development requiring permission. Creating an additional dwelling is such a change. Extending a house to provide more accommodation for the same household is not.
An annexe sits between the two. Where it works as part of a single household, sharing the house's facilities and life, it is ancillary and the planning unit is unchanged. Where it could and does function independently, it is a second dwelling.
The courts identify the planning unit by looking at the unit of occupation and whether the activities on it are functionally interlinked, with a separate planning unit arising where part of the land is used for a substantially different and separate purpose. Applied to an annexe, the practical test is whether the accommodation could be occupied by someone with no connection to the main house without any physical change.
The functional link officers look for
Case officers work through a familiar list, and the weight given to each item varies.
| Factor | Points towards ancillary | Points towards separate dwelling |
|---|---|---|
| Internal connection | Lockable but usable door into the main house | No internal connection at all |
| Cooking facilities | Kitchenette, limited provision, or none | Full independent kitchen |
| Services | Supply shared with the main house | Its own gas, electricity and water supplies |
| Access | Shared drive and shared front entrance | Own gate, path and front door off the street |
| Curtilage | Shared garden with no division | Fenced private garden |
| Postal address | Same address | Own number or name |
| Council tax | Treated as part of the dwelling or as an annexe | Separate band as a dwelling |
No single factor decides it. A detached building at the end of a long garden with its own kitchen, its own supplies and its own gate is a dwelling whatever the application says. The same building, interconnected by a glazed link, sharing the drive and on the house supply, with a kitchenette rather than a kitchen, is usually accepted as ancillary.
An important practical point. A separate metered supply is often installed for the occupier's convenience, and it is one of the strongest pieces of evidence against ancillary status. Submetering from the house achieves the same result for billing without creating the planning problem.
Permitted development, and why it rarely delivers an annexe
Class E of Part 1 permits outbuildings incidental to the enjoyment of the dwellinghouse, and the government's technical guidance is clear that such buildings must not be used as self-contained living accommodation and should not contain sleeping accommodation. So a garden annexe cannot be built under Class E.
An extension under Class A used as annexe accommodation is different, and it can work, provided the extension remains part of the single dwellinghouse. The accommodation stays within the house, with an internal connection, shared services and shared access. Build the same accommodation with its own front door and no internal link and you have changed the use of the planning unit, which Class A does not permit.
Heating a detached annexe raises its own permitted development questions, and heat pump installations carry limits and conditions of their own: see air source heat pumps and the conditions attached.
Occupancy conditions and what they do
Where an application is granted, expect two or three conditions.
A condition tying the accommodation to the main house, typically worded so that the annexe shall be used only for purposes ancillary to the use of the main dwelling and shall not be occupied as a separate dwelling. This is the workhorse condition.
A condition restricting occupation to a named relationship, such as a member of the household of the main dwelling or a person dependent on them. The courts have upheld conditions of this kind on annexe permissions, so they are not open to easy challenge, though the precise wording matters and overly personal drafting is sometimes criticised.
A condition removing permitted development rights, to prevent later extension or the creation of a separate curtilage.
Read the occupancy condition carefully before accepting it. A condition limited to a dependent relative becomes a problem when the relative dies and the family wants to use the space as a study or a guest room, because that use is outside the condition even though it is plainly ancillary. A condition framed around ancillary use to the main dwelling, without naming a relationship, is easier to live with and achieves the same planning purpose. Ask for that wording at the drafting stage.
Garden subdivision and the planning unit
Fencing off a garden for the annexe is one of the quickest ways to turn ancillary accommodation into a separate planning unit. The same applies to a separate bin store, a separate parking space marked out for the annexe, and a separate gate.
Keep the garden undivided on the submitted plans and say so in the Planning Statement. Where some privacy is wanted, show planting rather than fencing, and avoid drawing anything that reads as a boundary.
Overlooking is the other design issue, because annexe windows often face the neighbours at close range from a position where the house itself does not. The usual solutions are high-level or obscure-glazed windows, roof lights, and careful orientation, and the Design and Access Statement should show the sight lines. The same reasoning applies to raised areas and balconies, covered in Juliet balconies, terraces and overlooking on an extension.
Later severance and the enforcement risk
The common sequence is this: annexe built and occupied by a parent, parent dies, owners let the annexe or sell it off with a slice of garden. Both are a material change of use needing permission, and letting it as a self-contained unit also breaches the ancillary use condition.
A breach of condition notice can be served under section 187A of the 1990 Act, and there is no appeal against one. Enforcement time limits in England were changed by the Levelling-up and Regeneration Act 2023 to a single ten-year period for breaches, with transitional arrangements for earlier breaches, so check the current position rather than relying on the old four-year rule for changes of use to a single dwellinghouse.
The practical consequences surface on sale. A buyer's solicitor asks for the permission and the conditions, finds the ancillary use condition, and the annexe cannot be valued as a separate unit. Mortgage lenders take the same view.
If separation is the eventual aim, apply for it properly, with its own parking, amenity space, access and refuse provision assessed against the local plan's standards for a new dwelling. That is a different and harder application, and it is better attempted openly than discovered later.
What the application should say
Be explicit. A vague application invites a condition drafted defensively.
- State that the accommodation is ancillary to the main dwelling and describe the functional link in a sentence.
- Show the internal connection on the plans, or explain why there is none and how the link is maintained.
- Label the cooking facility accurately. A kitchenette is a kitchenette.
- Confirm that services will be taken from the main dwelling, with submetering if needed.
- Show the garden as undivided, with no separate access from the street.
- Say who the accommodation is for, and propose condition wording yourself, framed around ancillary use rather than a named person.
- Address overlooking, parking and refuse in the same document, because those are the points an objection will raise.
Community infrastructure levy is worth checking too. The regulations provide an exemption for residential annexes within the curtilage of the main dwelling, subject to conditions including that it is the only annexe and that the main dwelling is the applicant's principal residence, and the claim has to be made and acknowledged before work starts. Missing that sequence costs real money.
PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. This is general guidance, not 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.
Frequently asked questions
Does an annexe need planning permission?
Usually yes, unless it is formed as an extension that remains part of the single dwellinghouse under Class A, with an internal connection, shared services and shared access. A detached garden building cannot be an annexe under Class E, because the technical guidance is clear that such outbuildings must not be self-contained living accommodation.
What makes an annexe a separate dwelling?
The ability to function independently. A full kitchen, its own gas, electricity and water supplies, its own gate and front door from the street, a fenced private garden and a separate postal address together point firmly to a second dwelling. No single factor decides it, but separate metered supplies are among the strongest pieces of evidence.
Can the council restrict who lives in the annexe?
Yes. Conditions restricting occupation to a member of the household of the main dwelling, or to a person dependent on them, have been upheld by the courts. The wording matters, and a condition framed around ancillary use to the main dwelling is easier to live with than one naming a relationship that will eventually end.
Can I sell or let the annexe separately later?
Not without permission. Letting or selling it as a self-contained unit is a material change of use and will also breach the ancillary use condition, which can be enforced by a breach of condition notice with no right of appeal. Separation should be applied for openly, with parking, amenity space, access and refuse assessed as a new dwelling.
Is an annexe exempt from the community infrastructure levy?
The regulations provide an exemption for residential annexes within the curtilage of the main dwelling, subject to conditions including that it is the only annexe and that the main dwelling is the applicant's principal residence. The claim has to be made and acknowledged before work starts, so the sequence matters.
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.